60.Christians, JK. (2021) The Placenta's Role in Sexually Dimorphic Fetal Growth Strategies.Reproductive SciencesThe Placenta's Role in Sexually Dimorphic Fetal Growth Strategies
Placenta; Sex differences; Fetal growth; Nutrition; Pathology
Fetal sex affects the risk of pregnancy complications and the long-term effects of prenatal environment on health. Some have hypothesized that growth strategies differ between the sexes, whereby males prioritize growth whereas females are more responsive to their environment. This review evaluates the role of the placenta in such strategies, focusing on (1) mechanisms underlying sexual dimorphism in gene expression, (2) the nature and extent of sexual dimorphism in placental gene expression, (3) sexually dimorphic responses to nutrient supply, and (4) sexual dimorphism in morphology and histopathology. The sex chromosomes contribute to sex differences in placental gene expression, and fetal hormones may play a role later in development. Sexually dimorphic placental gene expression may contribute to differences in the prevalence of complications such as preeclampsia, although this link is not clear. Placental responses to nutrient supply frequently show sexual dimorphism, but there is no consistent pattern where one sex is more responsive. There are sex differences in the prevalence of placental histopathologies, and placental changes in pregnancy complications, but also many similarities. Overall, no clear patterns support the hypothesis that females are more responsive to the maternal environment, or that males prioritize growth. While male fetuses are at greater risk of a variety of complications, total prenatal mortality is higher in females, such that males exposed to early insults may be more likely to survive and be observed in studies of adverse outcomes. Going forward, robust statistical approaches to test for sex-dependent effects must be more widely adopted to reduce the incidence of spurious results. DOI PubMed
59.Christians, JK; Shergill, HK; Albert, AYK. (2021) Sex-dependent effects of prenatal food and protein restriction on offspring physiology in rats and mice: systematic review and meta-analyses.Biol. Sex Differ. 12 Sex-dependent effects of prenatal food and protein restriction on offspring physiology in rats and mice: systematic review and meta-analyses
Developmental origins; Developmental programming; Maternal nutrition; Malnutrition; Prenatal exposure
Background Males and females may experience different effects of early-life adversity on life-long health. One hypothesis is that male foetuses invest more in foetal growth and relatively less in placental growth, and that this makes them susceptible to poor nutrition in utero, particularly if nutrition is reduced part-way through gestation. Objectives Our objectives were to examine whether (1) food and/ or protein restriction in rats and mice has consistent sex-dependent effects, (2) sex-dependency differs between types of outcomes, and (3) males are more severely affected when restriction starts part-way through gestation. Data sources PubMed and Web of Science were searched to identify eligible studies. Study eligibility criteria Eligible studies described controlled experiments that restricted protein or food during gestation in rats or mice, examined physiological traits in offspring from manipulated pregnancies, and tested whether effects differed between males and females. Results Our search identified 292 articles, of which the full texts of 72 were assessed, and 65 were included for further synthesis. A majority (50) used Wistar or Sprague-Dawley rats and so these were the primary focus. Among studies in which maternal diet was restricted for the duration of gestation, no type of trait was consistently more severely affected in one particular sex, although blood pressure was generally increased in both sexes. Meta-analysis found no difference between sexes in the effect of protein restriction throughout gestation on blood pressure. Among studies restricting food in the latter half of gestation only, there were again few consistent sex-dependent effects, although three studies found blood pressure was increased in males only. Meta-analysis found that food restriction in the second half of gestation increased adult blood pressure in both sexes, with a significantly greater effect in males. Birthweight was consistently reduced in both sexes, a result confirmed by meta-analysis. Conclusions We found little support for the hypotheses that males are more affected by food and protein restriction, or that effects are particularly severe if nutrition is reduced part-way through gestation. However, less than half of the studies tested for sex by maternal diet interactions to identify sex-dependent effects. As a result, many reported sex-specific effects may be false positives. DOI PubMed
58. Rogowska, MD; Pena, UNV; Binning, N; Christians, JK. (2021) Recovery of the maternal skeleton after lactation is impaired by advanced maternal age but not by reduced IGF availability in the mouse.PLoS One 16 Recovery of the maternal skeleton after lactation is impaired by advanced maternal age but not by reduced IGF availability in the mouse
Background Lactation results in substantial maternal bone loss that is recovered following weaning. However, the mechanisms underlying this recovery, and in particular the role of insulin-like growth factor 1 (IGF-I), is not clear. Furthermore, there is little data regarding whether recovery is affected by advanced maternal age. Methods Using micro-computed tomography, we studied bone recovery following lactation in mice at 2, 5 and 7 months of age. We also investigated the effects of reduced IGF-I availability using mice lacking PAPP-A2, a protease of insulin-like growth factor binding protein 5 (IGFBP-5). Results In 2 month old mice, lactation affected femoral trabecular and cortical bone, but only cortical bone showed recovery 3 weeks after weaning. This recovery was not affected by deletion of the Pappa2 gene. The amount of trabecular bone was reduced in 5 and 7 month old mice, and was not further reduced by lactation. However, the recovery of cortical bone was impaired at 5 and 7 months compared with at 2 months. Conclusions Recovery of the maternal skeleton after lactation is impaired in moderately-aged mice compared with younger mice. Our results may be relevant to the long-term effects of breastfeeding on the maternal skeleton in humans, particularly given the increasing median maternal age at childbearing. DOI PubMed
57. Rubio, L; Vargas, A; Rivera, P; Lopez-Gambero, AJ; Tovar, R; Christians, JK; Martin-de-las-Heras, S; de Fonseca, FR; Chowen, JA; Argente, J; Suarez, J. (2021) Recombinant IGF-1 Induces Sex-Specific Changes in Bone Composition and Remodeling in Adult Mice with Pappa2 Deficiency.Int. J. Mol. Sci. 22 Recombinant IGF-1 Induces Sex-Specific Changes in Bone Composition and Remodeling in Adult Mice with Pappa2 Deficiency
apatite; bone; collagen; growth; IGFBP; pappalysin; sex difference; Pappa2 deficiency
Deficiency of pregnancy-associated plasma protein-A2 (PAPP-A2), an IGF-1 availability regulator, causes postnatal growth failure and dysregulation of bone size and density. The present study aimed to determine the effects of recombinant murine IGF-1 (rmIGF-1) on bone composition and remodeling in constitutive Pappa2 knock-out (ko/ko) mice. To address this challenge, X-ray diffraction (XRD), attenuated total reflection-fourier transform infra-red (ATR-FTIR) spectroscopy and gene expression analysis of members of the IGF-1 system and bone resorption/formation were performed. Pappa2(ko/ko) mice (both sexes) had reduced body and bone length. Male Pappa2(ko/ko) mice had specific alterations in bone composition (mineral-to-matrix ratio, carbonate substitution and mineral crystallinity), but not in bone remodeling. In contrast, decreases in collagen maturity and increases in Igfbp3, osteopontin (resorption) and osteocalcin (formation) characterized the bone of Pappa2(ko/ko) females. A single rmIGF-1 administration (0.3 mg/kg) induced short-term changes in bone composition in Pappa2(ko/ko) mice (both sexes). rmIGF-1 treatment in Pappa2(ko/ko) females also increased collagen maturity, and Igfbp3, Igfbp5, Col1a1 and osteopontin expression. In summary, acute IGF-1 treatment modifies bone composition and local IGF-1 response to bone remodeling in mice with Pappa2 deficiency. These effects depend on sex and provide important insights into potential IGF-1 therapy for growth failure and bone loss and repair. DOI PubMed
56. Baltayeva, J; Konwar, C; Castellana, B; Mara, DL; Christians, JK; Beristain, AG. (2020) Obesogenic diet exposure alters uterine natural killer cell biology and impairs vasculature remodeling in mice.Biol. Reprod. 102: 63-75 Obesogenic diet exposure alters uterine natural killer cell biology and impairs vasculature remodeling in mice
pregnancy; natural killer cell; uterus; decidua; placenta; diet-induced obesity; spiral artery remodeling; high-fat/high-sucrose diet; gene expression; gene microarray
Prepregnancy obesity associates with adverse reproductive outcomes that impact maternal and fetal health. While obesity-driven mechanisms underlying adverse pregnancy outcomes remain unclear, local uterine immune cells are strong but poorly studied candidates. Uterine immune cells, particularly uterine natural killer cells (uNKs), play central roles in orchestrating developmental events in pregnancy. However, the effect of obesity on uNK biology is poorly understood. Using an obesogenic high-fat/high-sugar diet (HFD) mouse model, we set out to examine the effects of maternal obesity on uNK composition and establishment of the maternal-fetal interface. HFD exposure resulted in weight gain-dependent increases in systemic inflammation and rates of fetal resorption. While HFD did not affect total uNK frequencies, HFD exposure did lead to an increase in natural cytotoxicity receptor-1 expressing uNKs as well as overall uNK activity. Importantly, HFD-associated changes in uNK coincided with impairments in uterine artery remodeling in mid but not late pregnancy. Comparison of uNK mRNA transcripts from control and HFD mice identified HFD-directed changes in genes that play roles in promoting activity/cytotoxicity and vascular biology. Together, this work provides new insight into how obesity may impact uNK processes central to the establishment of the maternal-fetal interface in early and mid pregnancy. Moreover, these findings shed light on the cellular processes affected by maternal obesity that may relate to overall pregnancy health. Summary sentence High-fat diet promotes uterine NK cell activation in pregnancy and associates with impaired vascular remodeling within the uterus and drives altered uterine NK gene expression. DOI PubMed
55.Christians, JK; Munoz, MFH. (2020) Pregnancy complications recur independently of maternal vascular malperfusion lesions.PLoS One 15 Pregnancy complications recur independently of maternal vascular malperfusion lesions
Background Spontaneous abortions, intrauterine growth restriction, and preeclampsia are thought to be caused by defective placentation and are associated with increased risk of adverse outcomes in subsequent pregnancies. However, it is not known whether the recurrence of adverse outcomes is associated with the recurrence of placental pathology. We hypothesized that recurrent maternal vascular malperfusion (MVM) underlies the recurrence of adverse outcomes. Methods Using data from the National Collaborative Perinatal Project, we assessed the recurrence of pregnancy complications and MVM lesions (N = 3865), associations between a history of spontaneous abortions and MVM lesions or adverse outcomes in subsequent pregnancies (N = 8312), and whether the recurrence of pregnancy complications occurred independently of the presence of MVM lesions. Results The odds of an MVM lesion were higher for a woman who had had an MVM lesion in a previous pregnancy (aOR = 1.6; 95% CI 1.3-1.9), although this was marginally non-significant after adjusting for covariates such as gestational age, race and BMI. The odds of preeclampsia, a small-for-gestational-age infant, premature delivery and early pregnancy loss were 2.7-5.0 times higher if there had been that same adverse outcome in a previous pregnancy. A history of spontaneous abortions was associated with higher risk of a small-forgestational-age baby (aOR = 2.4; 95% CI 1.7-3.4) and prematurity (aOR = 5.1; 95% CI 2.3-11.5 for extremely preterm), but not preeclampsia. The recurrence of adverse outcomes was significant when restricting analyses to women without MVM lesions. Similarly, associations between adverse outcomes and previous spontaneous abortions were significant when statistically controlling for the presence of MVM lesions, or excluding pregnancies with MVM lesions. Conclusions Women with adverse outcomes in one pregnancy are at higher risk of complications in subsequent pregnancies. However, there is significant recurrence of adverse outcomes even in the absence of MVM. DOI PubMed
54. Virginkar, N; Christians, JK. (2020) Maternal Obesity Does Not Exacerbate the Effects of LPS Injection on Pregnancy Outcomes in Mice.Biology-Basel 9 Maternal Obesity Does Not Exacerbate the Effects of LPS Injection on Pregnancy Outcomes in Mice
obesity; inflammation; pregnancy; lipopolysaccharide; fetal growth; spontaneous abortion
Simple Summary Obesity increases the risk of problems during pregnancy, potentially due to inappropriate activation of the immune system. We predicted that, because of this immune activation, obesity in mice would exacerbate the effects of lipopolysaccharide (LPS), a substance that mimics infection, impairs fetal growth and leads to pregnancy loss in animal models. Mice were fed a high- or low-fat diet for thirteen weeks prior to mating, and then received an LPS or control injection during pregnancy. Treatment with LPS induced pregnancy loss in some mice, as expected. However, LPS did not have more severe effects in females fed the high-fat diet, who were heavier. Our results therefore do not support the hypothesis that an otherwise healthy obese pregnancy can be driven to an adverse outcome by a low-level infection. Our study improves the understanding of why obese women are at greater risk of adverse pregnancy outcomes. In doing so, it will contribute to future studies that seek to determine how obese pregnancies at risk of adverse outcomes can be distinguished from healthy obese pregnancies. Obesity increases the risk of a number of pregnancy complications, potentially due to chronic inflammation. We predicted that an obesogenic high-fat diet (HFD) in mice would create an inflammatory environment that would exacerbate the effects of lipopolysaccharide (LPS), an inflammatory insult, administered during pregnancy. Females were placed on a HFD or a low-fat diet (LFD) prior to mating, injected with 2 mu g LPS or control on gestational day 7 and collected on day 14. Treatment with LPS increased the odds that a female thought to be pregnant at injection had no conceptuses at day 14 (p= 0.024), suggesting that injection with LPS was more likely to induce complete abortion. However, there was no effect of diet on the odds of having no conceptuses at day 14 and no interaction between diet and LPS injection. Diet and LPS injection had no effect on the number of viable fetuses in females still pregnant at day 14. For fetal weight, there was a significant interaction between diet and treatment (p= 0.017), whereby LPS reduced fetal weight in HFD females but not in LFD females. However, LPS treatment of HFD females reduced fetal weight to that observed in control-injected LFD females. Although LPS increased the odds of abortion, there was little evidence that a HFD exacerbated the effects of LPS. DOI PubMed
53.Christians, JK; Amiri, N; Schipilow, JD; Zhang, SW; May-Rashke, KI. (2019) Pappa2 deletion has sex- and age-specific effects on bone in mice.Growth Horm. IGF Res. 44: 6-10 Pappa2 deletion has sex- and age-specific effects on bone in mice
Bone; Insulin-like growth factor; IGF; Insulin-like growth factor binding protein; IGFBP; Pappalysin; PAPP-A2
Objective: In humans, loss-of-function mutations in the gene encoding pregnancy-associated pregnancy protein-A2 cause short stature and slightly reduced bone density. The goal of this study was to determine the effects of Pappa2 deletion on bone in mice. Design: Pappa2 deletion mice and littermate controls were culled at 10, 19 or 30 weeks of age and femurs were analysed by micro-computed tomography. Serum markers of bone turnover and insulin-like growth factor binding protein 5 (IGFBP-5), a proteolytic target of PAPP-A2, were measured by ELISA. Results: At 10 and 19 weeks of age, Pappa2 deletion mice had slightly reduced trabecular parameters, but by 19 weeks of age, female deletion mice had increased cortical tissue mineral density, and this trait was increased by a small amount in deletion mice of both sexes at 30 weeks. Cortical area fraction was increased in Pappa2 deletion mice at all ages. Deletion of Pappa2 increased circulating IGFBP-5 levels and reduced markers of bone turnover (PINP and TRACP 5b). Conclusions: PAPP-A2 contributes to the regulation of bone structure and mass in mice, likely through control of IGFBP-5 levels. The net effect of changes in bone formation and resorption depend on sex and age, and differ between trabecular and cortical bone. DOI PubMed
52.Christians, JK; Grynspan, D. (2019) Placental villous hypermaturation is associated with improved neonatal outcomes.Placenta 76: 1-5 Placental villous hypermaturation is associated with improved neonatal outcomes
Accelerated maturation; Compensation; Hypermaturation; Pathology; Preterm; Outcome
Introduction: Accelerated placental maturation is considered a sign of maternal vascular malperfusion, and is often interpreted as an adaptive, compensatory response by the placenta. We tested this interpretation by comparing outcomes in pregnancies with and without accelerated maturation. Methods: Using data from the National Collaborative Perinatal Project, we categorized preterm placentas (24-34 weeks, inclusive; 2525 births) by whether they showed placental villous hypermaturation (PVH), i.e., had the appearance of a placenta of 37 weeks or over upon microscopic examination. We assessed whether PVH was associated with maternal race, maternal BMI, fetal sex, type of preterm birth, preeclampsia, signs of infection or inflammation or placental abruption. We also assessed whether placentas showing PVH were associated with improved outcomes in terms of survival, Apgar score, or oxygen use. Results: PVH was more common in preeclamptic pregnancies and less common in pregnancies complicated by placental abruption or showing signs of placental infection or inflammation. Adjusting for potentially confounding factors, PVH was associated with reduced odds of fetal death, death between birth and 120 days of age, low Apgar scores and oxygen use. PVH was also associated with higher birthweights for gestational age. When correcting for the effect of birthweight, the association between PVH and reduced fetal and neonatal death remained significant. Discussion: Accelerated placental maturation, as manifested by PVH, is associated with improved outcomes. Our work therefore supports the hypothesis that accelerated maturation is a compensatory response by the placenta to improve its transport capacity in specific pregnancy complications. DOI PubMed
51.Christians, JK; Lennie, KI; Wild, LK; Garcha, R. (2019) Effects of high-fat diets on fetal growth in rodents: a systematic review.Reprod. Biol. Endocrinol. 17: 39 Effects of high-fat diets on fetal growth in rodents: a systematic review
Developmental origins; Fetal growth; Maternal nutrition; Obesity
Background: Maternal nutrition during pregnancy has life-long consequences for offspring. However, the effects of maternal overnutrition and/ or obesity on fetal growth remain poorly understood, e.g., it is not clear why birthweight is increased in some obese pregnancies but not in others. Maternal obesity is frequently studied using rodents on high-fat diets, but effects on fetal growth are inconsistent The purpose of this review is to identify factors that contribute to reduced or increased fetal growth in rodent models of maternal overnutrition. Methods: We searched Web of Science and screened 2173 abstracts and 328 full texts for studies that fed mice or rats diets providing similar to 45% or similar to 60% calories from fat for 3 weeks or more prior to pregnancy. We identified 36 papers matching the search criteria that reported birthweight or fetal weight. Results: Studies that fed 45% fat diets to mice or 60% fat diets to rats generally did not show effects on fetal growth. Feeding a 45% fat diet to rats generally reduced birth and fetal weight. Feeding mice a 60% fat diet for 4-9 weeks prior to pregnancy tended to increase in fetal growth, whereas feeding this diet for a longer period tended to reduce fetal growth. Conclusions: The high-fat diets used most often with rodents do not closely match Western diets and frequently reduce fetal growth, which is not a typical feature of obese human pregnancies. Adoption of standard protocols that more accurately mimic effects on fetal growth observed in obese human pregnancies will improve translational impact in this field.Website DOI PubMed
48. Chin, EH; Schmidt, KL; Martel, KM; Wong, CK; Hamden, JE; Gibson, WT; Soma, KK; Christians, JK. (2017) A maternal high-fat, high-sucrose diet has sexspecific effects on fetal glucocorticoids with little consequence for offspring metabolism and voluntary locomotor activity in mice.PLoS One 12 A maternal high-fat, high-sucrose diet has sexspecific effects on fetal glucocorticoids with little consequence for offspring metabolism and voluntary locomotor activity in mice
Maternal overnutrition and obesity during pregnancy can have long-term effects on offspring physiology and behaviour. These developmental programming effects may be mediated by fetal exposure to glucocorticoids, which is regulated in part by placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) type 1 and 2. We tested whether a maternal high-fat, high-sucrose diet would alter expression of placental 11 beta-HSD1 and 2, thereby increasing fetal exposure to maternal glucocorticoids, with downstream effects on offspring physiology and behaviour. C57BL/6J mice were fed a high-fat, high-sucrose (HFHS) diet or a nutrient-matched low-fat, no-sucrose control diet prior to and during pregnancy and lactation. At day 17 of gestation, HFHS dams had similar to 20% lower circulating corticosterone levels than controls. Furthermore, there was a significant interaction between maternal diet and fetal sex for circulating corticosterone levels in the fetuses, whereby HFHS males tended to have higher corticosterone than control males, with no effect in female fetuses. However, placental 11 beta-HSD1 or 11 beta-HSD2 expression did not differ between diets or show an interaction between diet and sex. To assess potential long-term consequences of this sex-specific effect on fetal corticosterone, we studied locomotor activity and metabolic traits in adult offspring. Despite a sex-specific effect of maternal diet on fetal glucocorticoids, there was little evidence of sex-specific effects on offspring physiology or behaviour, although HFHS offspring of both sexes had higher circulating corticosterone at 9 weeks of age. Our results suggest the existence of as yet unknown mechanisms that mitigate the effects of altered glucocorticoid exposure early in development, making offspring resilient to the potentially negative effects of a HFHS maternal diet. DOI
47.Christians, JK; Leavey, K; Cox, BJ. (2017) Associations between imprinted gene expression in the placenta, human fetal growth and preeclampsia.Biology Letters 13 Associations between imprinted gene expression in the placenta, human fetal growth and preeclampsia
placenta; imprinting; preeclampsia; intrauterine growth restriction; kinship theory
Genomic imprinting is essential for normal placental and fetal growth. One theory to explain the evolution of imprinting is the kinship theory (KT), which predicts that genes that are paternally expressed will promote fetal growth, whereas maternally expressed genes will suppress growth. We investigated the expression of imprinted genes using microarray measurements of expression in term placentae. Correlations between birthweight and the expression levels of imprinted genes were more significant than for non-imprinted genes, but did not tend to be positive for paternally expressed genes and negative for maternally expressed genes. Imprinted genes were more dysregulated in preeclampsia (a disorder associated with placental insufficiency) than randomly selected genes, and we observed an excess of patterns of dysregulation in preeclampsia that would be expected to reduce nutrient allocation to the fetus, given the predictions of the KT. However, we found no evidence of coordinated regulation among these imprinted genes. A few imprinted genes have previously been shown to be associated with fetal growth and preeclampsia, and our results indicate that this is true for a broader set of imprinted genes. DOI
46. Hodgson, ZG; Saxell, L; Christians, JK. (2017) An evaluation of Interprofessional group antenatal care: a prospective comparative study.BMC Pregnancy Childbirth 17 An evaluation of Interprofessional group antenatal care: a prospective comparative study
Connecting pregnancy; Group care; Interprofessional; Antenatal care; Perinatal outcomes; Client satisfaction
Background: Maternal and neonatal outcomes are influenced by the nature of antenatal care. Standard pregnancy care is provided on an individual basis, with one-on-one appointments between a client and family doctor, midwife or obstetrician. A novel, group-based antenatal care delivery model was developed in the United States in the 1990s and is growing in popularity beyond the borders of the USA. The purpose of this study was to evaluate outcomes in clients receiving interprofessional group perinatal care versus interprofessional individual care in a Canadian setting. Methods: Clients attending the South Community Birth Program (SCBP), an interprofessional, collaborative, primary care maternity program, offering both individual and group care, were invited to participate in the study. Pregnancy knowledge and satisfaction scores, and perinatal outcomes were compared between those receiving group versus individual care. Chi-square tests, general linear models and logistic regression were used to compare the questionnaire scores and perinatal outcomes between cohorts. Results: Three hundred three clients participated in the study. Group care was comparable to individual care in terms of mode of birth, gestational age at birth, infant birth weight, breastfeeding rates, pregnancy knowledge, preparedness for labour and baby care, and client satisfaction. The rates of adverse perinatal outcomes were extremely low amongst SCBP clients, regardless of the type of care received (preterm birth rates similar to 5%). Breastfeeding rates were very high amongst all study participants (> 78% exclusive breastfeeding), as were measures of pregnancy knowledge and satisfaction. Conclusions: This is the first Canadian study to compare outcomes in clients receiving interprofessional group care versus individual care. Our observation that interprofessional group care outcomes and satisfaction were as good as interprofessional individual care has important implications for the antenatal care of clients and for addressing the projected maternity provider crisis facing Canada, particularly in small and rural communities. Further study of group-based care including not only client satisfaction, but also provider satisfaction, is needed. In addition, research into the role of interprofessional care in meeting the needs and improving perinatal outcomes of different populations is necessary. DOI
45.Christians, JK; Beristain, AG. (2016) ADAM12 and PAPP-A: Candidate regulators of trophoblast invasion and first trimester markers of healthy trophoblasts.Cell Adhesion & Migration 10: 147-153 ADAM12 and PAPP-A: Candidate regulators of trophoblast invasion and first trimester markers of healthy trophoblasts
A disintegrin and metalloproteinase 12; ADAM12; fetal growth restriction; invasion; PAPP-A; preeclampsia; pregnancy-associated plasma protein-A; trophoblast
Proper placental development and function is crucial for a healthy pregnancy, and there has been substantial research to identify markers of placental dysfunction for the early detection of pregnancy complications. Low first-trimester levels of a disintegrin and metalloproteinase 12 (ADAM12) and pregnancy-associated plasma protein-A (PAPP-A) have been consistently associated with the subsequent development of preeclampsia and fetal growth restriction. These molecules are both metalloproteinases secreted by the placenta that cleave insulin-like growth factor binding proteins (IGFBPs), although ADAM12 also has numerous other substrates. Recent work has identified ADAM12, and particularly its shorter variant, ADAM12S, as a regulator of the migration and invasion of trophoblasts into the lining of the uterus, a critical step in normal placental development. While the mechanisms underlying this regulation are not yet clear, they may involve the liberation of heparin-binding EGF-like growth factor (HB-EGF) and/or IGFs from IGFBPs. In contrast, there has been relatively little functional work examining PAPP-A or the IGFBP substrates of ADAM12 and PAPP-A. Understanding the functions of these markers and the mechanisms underlying their association with disease could improve screening strategies and enable the development of new therapeutic interventions. DOI
44. Fronstin, RB; Christians, JK; Williams, TD. (2016) Experimental reduction of haematocrit affects reproductive performance in European starlings.Functional Ecology 30: 398-409 Experimental reduction of haematocrit affects reproductive performance in European starlings
cost of reproduction; haemoglobin; interindividual variation; reproductive anaemia; reproductive success
1. Given the function of haemoglobin and observed increases in haematocrit during periods of increased energetic demands, haematocrit and haemoglobin are assumed to be related to aerobic capacity. Reductions in haematocrit and haemoglobin during reproduction are similar in magnitude to increases associated with aerobically demanding activities, and therefore, we sought to investigate whether these reductions in haematology have consequences for reproductive performance. 2. We analysed associations between natural variation in haematology in free-living European starlings (Sturnus vulgaris) and reproductive performance. To test whether transient reductions in haematology during different stages of reproduction (egg production and late incubation/early chick rearing) affected measures of reproductive performance, we also manipulated haematology using phenylhydrazine (PHZ), which lyses red blood cells. 3. To investigate effects of reductions of haematology during egg-laying, we treated females with PHZ or saline (control) upon completion of their unmanipulated first clutch and removed eggs to induce the production and rearing of a replacement clutch. To investigate effects of reductions of haematology during chick rearing, we treated females during incubation of the unmanipulated first clutch and then monitored the subsequent hatching and rearing of the clutch. 4. Individuals with higher haematocrit and haemoglobin initiated nesting earlier. Furthermore, higher haemoglobin levels during incubation were associated with a greater number of chicks fledged. 5. PHZ treatment prior to egg production resulted in a significant delay in the laying of replacement clutches, but had no effect on provisioning rate or the size or number of chicks fledged. PHZ treatment during incubation and early chick rearing resulted in decreased hatchling mass in all years and a decrease in the size and number of fledglings in one of 2years. The year that the effect of PHZ was observed appeared to be a particularly difficult year, as hatchling mass, brood size at hatching and at fledging were low among control females compared to other years. 6. Our results suggest that a reduction in haematology during reproduction can be functionally significant, but that these costs are context-dependent. DOI
43. Fronstin, RB; Doucet, SM; Christians, JK. (2016) Haematocrit, eggshell colouration and sexual signaling in the European starling (Sturnus vulgaris).BMC Ecology 16 Haematocrit, eggshell colouration and sexual signaling in the European starling (Sturnus vulgaris)
Eggshell colour; Haematocrit; Sexual signal
Background: One hypothesis to explain the blue-green colour of the eggs of many bird species is that it is a sexually-selected signal of the laying female's quality, which males use to determine their investment. This hypothesis requires that eggshell pigmentation carries a cost or is otherwise linked to female quality. One potential cost is that biliverdin, a haem derivative and the pigment responsible for eggshell colouration, is limiting. To assess this potential cost, we attempted to manipulate haematocrit and haemoglobin in free-living European starlings (Sturnus vulgaris Linnaeus). Upon collecting unmanipulated first clutches, we treated females with phenylhydrazine (PHZ), a haemolytic agent, and measured the blue-green chroma and reproductive performance of replacement clutches. We also investigated whether eggshell colour was associated with haematocrit or haemoglobin levels in unmanipulated first clutches. To test whether eggshell colour might act as a sexual signal, we examined associations between eggshell colour and reproductive performance, as well as the provisioning rate of the male. Results: PHZ-treatment did not affect eggshell colour in replacement clutches. In unmanipulated first clutches, eggshell colour was not correlated with haematocrit or haemoglobin levels. Eggshell colour was correlated with female mass in unmanipulated first clutches but not replacement clutches. Chicks from eggs with higher eggshell colour had higher haemoglobin levels and longer tarsi just prior to fledging, suggesting that eggshell colour could reflect brood quality. However, eggshell colour was not correlated with the provisioning rate of the male or any other measure of reproductive performance. Conclusions: We found no evidence to support the hypothesis that the availability of resources required for the synthesis of pigment limits eggshell colour in European starlings, or that eggshell colour is used by males to determine their level of reproductive investment. We found little evidence that eggshell colour is correlated with female or offspring quality in this species. DOI
41. Chin, EH; Christians, JK. (2015) When are sex-specific effects really sex-specific?Journal of Developmental Origins of Health and Disease 6: 438-442 When are sex-specific effects really sex-specific?
developmental programming; developmental origins of health and disease; sex-specific effects; Bayesian
We examined developmental programming studies that reported sex-specific effects published between 2012 and 2014, and examined whether the authors reported a statistical approach to explicitly test whether the effect of treatment differed between the sexes, for example, a sex by treatment interaction term. Less than half of the studies that reported sex-specific effects described explicitly testing whether effects were indeed sex-specific; in most cases, an effect was considered 'sex-specific' if it was significant in one sex but not the other. This is not a robust approach, since significance in one sex and lack of significance in the other sex does not imply a significant difference between the sexes. However, sample size often limits statistical power to detect interactions. We suggest that if the effect is significant in only one sex, but the interaction term is not significant, alternative solutions would be to present the confidence intervals for the effect size for each sex, or using Bayesian approaches to calculate the probability that the effect sizes differ between the sexes. We present a simple example of a Bayesian analysis to illustrate that this approach is reasonably easy to implement and interpret.PDF DOI
37. Crosley, EJ; Durland, U; Seethram, K; MacRae, S; Gruslin, A; Christians, JK. (2014) First-Trimester Levels of PregnancyAssociated Plasma Protein A2 ( PAPP-A2) in the Maternal Circulation Are Elevated in Pregnancies That Subsequently Develop Preeclampsia.Reproductive Sciences 21: 754-760 First-Trimester Levels of PregnancyAssociated Plasma Protein A2 ( PAPP-A2) in the Maternal Circulation Are Elevated in Pregnancies That Subsequently Develop Preeclampsia
PAPP-A2; preeclampsia; small-for-gestational-age
Recent studies have consistently found pregnancy-associated plasma protein A2 (PAPP-A2) to be upregulated in preeclamptic placentae at term. We tested whether first-trimester circulating PAPP-A2 levels differed between complicated and uncomplicated pregnancies. We measured maternal PAPP-A2 levels at 10 to 14 weeks of gestational age in 17 pregnancies resulting in small-for-gestational-age (SGA) infants, 6 which developed preeclampsia (PE), 1 which developed PE and resulted in an SGA infant, and 37 gestational age-matched controls. The concentration of the PAPP-A2 isoform corresponding to the full-length protein was significantly higher in pregnancies that developed PE (35 ng/mL) compared with those that did not (23 ng/mL; P < .044). In contrast, we found no difference in PAPP-A2 levels between pregnancies that did or did not result in an SGA infant. The upregulation of PAPP-A2 that has previously been observed in PE at term appears to begin early in pregnancy, well before the symptoms develop. DOI
34. Crosley, EJ; Elliot, MG; Christians, JK; Crespi, BJ. (2013) Placental invasion, preeclampsia risk and adaptive molecular evolution at the origin of the great apes: Evidence from genome-wide analyses.Placenta 34: 127-132 Placental invasion, preeclampsia risk and adaptive molecular evolution at the origin of the great apes: Evidence from genome-wide analyses
DEEP TROPHOBLAST INVASION; MATRIX-METALLOPROTEINASES; NONHUMAN-PRIMATES; INSULIN-RECEPTORS; LOWLAND GORILLA; GENE-EXPRESSION; CELL INVASION; ACTIVIN-A; PREGNANCY; INHIBIN
Introduction: Recent evidence from chimpanzees and gorillas has raised doubts that preeclampsia is a uniquely human disease. The deep extravillous trophoblast (EVT) invasion and spiral artery remodeling that characterizes our placenta (and is abnormal in preeclampsia) is shared within great apes, setting Homininae apart from Hylobatidae and Old World Monkeys, which show much shallower trophoblast invasion and limited spiral artery remodeling. We hypothesize that the evolution of a more invasive placenta in the lineage ancestral to the great apes involved positive selection on genes crucial to EVT invasion and spiral artery remodeling. Furthermore, identification of placentally-expressed genes under selection in this lineage may identify novel genes involved in placental development. Methods: We tested for positive selection in approximately 18,000 genes using the ratio of non-synonymous to synonymous amino acid substitution for protein-coding DNA. DAVID Bioinformatics Resources identified biological processes enriched in positively selected genes, including processes related to EVT invasion and spiral artery remodeling. Results: Analyses revealed 295 and 264 genes under significant positive selection on the branches ancestral to Hominidae (Human, Chimp, Gorilla, Orangutan) and Homininae (Human, Chimp, Gorilla), respectively. Gene ontology analysis of these gene sets demonstrated significant enrichments for several functional gene clusters relevant to preeclampsia risk, and sets of placentally-expressed genes that have been linked with preeclampsia and/or trophoblast invasion in other studies. Conclusion: Our study represents a novel approach to the identification of candidate genes and amino acid residues involved in placental pathologies by implicating them in the evolution of highly-invasive placenta. (C) 2012 Elsevier Ltd. All rights reserved. DOI
33. Cheema, MS; Christians, JK. (2011) Virulence in an insect model differs between mating types in Aspergillus fumigatus.Medical Mycology 49 Virulence in an insect model differs between mating types in Aspergillus fumigatus
Aspergillus; virulence; variability; Galleria; mating type
Aspergillus fumigatus is an opportunistic fungal pathogen that has recently been found to undergo sexual reproduction. Previous work suggested that invasiveness differs between mating types, and in the present study we tested whether virulence differs between mating types in an in vivo model, i.e., larvae of the wax moth Galleria mellonella. We measured virulence of 20 A. fumigatus isolates; three MAT1-1 isolates of environmental origin, five MAT1-1 isolates of clinical origin, seven MAT1-2 isolates of environmental origin and five MAT1-2 isolates of clinical origin. For each isolate, we measured virulence in six replicates and for each replicate, conidia were grown, harvested, and counted independently, and 2,500 colony forming units were injected into each of 10 G. mellonella larvae. Virulence differed between mating types, with lower survival in larvae injected with MAT1-1 isolates. Virulence also differed between clinical and environmental isolates, but surprisingly larvae injected with environmental isolates had lower survival. Identification of the mechanisms underlying variation in virulence may identify novel targets for the treatment of Aspergillus infections.Website DOI
32.Christians, JK; Cheema, MS; Vergara, IA; Watt, CA; Pinto, LJ; Chen, NS; Moore, MM. (2011) Quantitative Trait Locus (QTL) Mapping Reveals a Role for Unstudied Genes in Aspergillus Virulence.PLOS One 6 Quantitative Trait Locus (QTL) Mapping Reveals a Role for Unstudied Genes in Aspergillus Virulence
Infections caused by the fungus Aspergillus are a major cause of morbidity and mortality in immunocompromised populations. To identify genes required for virulence that could be used as targets for novel treatments, we mapped quantitative trait loci (QTL) affecting virulence in the progeny of a cross between two strains of A. nidulans (FGSC strains A4 and A91). We genotyped 61 progeny at 739 single nucleotide polymorphisms (SNP) spread throughout the genome, and constructed a linkage map that was largely consistent with the genomic sequence, with the exception of one potential inversion of similar to 527 kb on Chromosome V. The estimated genome size was 3705 cM and the average intermarker spacing was 5.0 cM. The average ratio of physical distance to genetic distance was 8.1 kb/cM, which is similar to previous estimates, and variation in recombination rate was significantly positively correlated with GC content, a pattern seen in other taxa. To map QTL affecting virulence, we measured the ability of each progeny strain to kill model hosts, larvae of the wax moth Galleria mellonella. We detected three QTL affecting in vivo virulence that were distinct from QTL affecting in vitro growth, and mapped the virulence QTL to regions containing 7-24 genes, excluding genes with no sequence variation between the parental strains and genes with only synonymous SNPs. None of the genes in our QTL target regions have been previously associated with virulence in Aspergillus, and almost half of these genes are currently annotated as "hypothetical". This study is the first to map QTL affecting the virulence of a fungal pathogen in an animal host, and our results illustrate the power of this approach to identify a short list of unknown genes for further investigation. DOI
31. Gorman, KF; Christians, JK; Parent, J; Ahmadi, R; Weigel, D; Dreyer, C; Breden, F. (2011) A major QTL controls susceptibility to spinal curvature in the curveback guppy.BMC Genetics 12 A major QTL controls susceptibility to spinal curvature in the curveback guppy
Background: Understanding the genetic basis of heritable spinal curvature would benefit medicine and aquaculture. Heritable spinal curvature among otherwise healthy children (i.e. Idiopathic Scoliosis and Scheuermann kyphosis) accounts for more than 80% of all spinal curvatures and imposes a substantial healthcare cost through bracing, hospitalizations, surgery, and chronic back pain. In aquaculture, the prevalence of heritable spinal curvature can reach as high as 80% of a stock, and thus imposes a substantial cost through production losses. The genetic basis of heritable spinal curvature is unknown and so the objective of this work is to identify quantitative trait loci (QTL) affecting heritable spinal curvature in the curveback guppy. Prior work with curveback has demonstrated phenotypic parallels to human idiopathic-type scoliosis, suggesting shared biological pathways for the deformity. Results: A major effect QTL that acts in a recessive manner and accounts for curve susceptibility was detected in an initial mapping cross on LG 14. In a second cross, we confirmed this susceptibility locus and fine mapped it to a 5 cM region that explains 82.6% of the total phenotypic variance. Conclusions: We identify a major QTL that controls susceptibility to curvature. This locus contains over 100 genes, including MTNR1B, a candidate gene for human idiopathic scoliosis. The identification of genes associated with heritable spinal curvature in the curveback guppy has the potential to elucidate the biological basis of spinal curvature among humans and economically important teleosts. DOI
30. Wagner, PK; Otomo, A; Christians, JK. (2011) Regulation of pregnancy-associated plasma protein A2 (PAPPA2) in a human placental trophoblast cell line (BeWo).Reproductive Biology and Endocrinology 9 Regulation of pregnancy-associated plasma protein A2 (PAPPA2) in a human placental trophoblast cell line (BeWo)
Background: Pregnancy-associated plasma protein A2 (PAPPA2) is an insulin-like growth factor-binding protein (IGFBP) protease expressed at high levels in the placenta and upregulated in pregnancies complicated by preeclampsia and HELLP (Hemolytic anemia, Elevated Liver enzymes, and Low Platelet count) syndrome. However, it is unclear whether elevated PAPPA2 expression causes abnormal placental development, or whether upregulation compensates for placental pathology. In the present study, we investigate whether PAPPA2 expression is affected by hypoxia, oxidative stress, syncytialization factors or substances known to affect the expression of PAPPA2's paralogue, PAPPA. Methods: BeWo cells, a model of placental trophoblasts, were treated with one of the following: hypoxia (2% O2), oxidative stress (20 microM hydrogen peroxide), forskolin (10 microM and 100 microM), TGF-beta (10 and 50 ng/mL), TNF-alpha (100 ng/mL), IL-1beta (100 ng/mL) or PGE2 (1 microM). We used quantitative RT-PCR (qRT-PCR) to quantify the mRNA levels of PAPPA2, as well as those of PAPPA and ADAM12 since these proteases have similar substrates and are also highly expressed in the placenta. Where we observed significant effects on PAPPA2 mRNA levels, we tested for effects at the protein level using an in-cell Western assay. Results: Hypoxia, but not oxidative stress, caused a 47-fold increase in PAPPA2 mRNA expression, while TNF-alpha resulted in a 6-fold increase, and both of these effects were confirmed at the protein level. PGE2 resulted in a 14-fold upregulation of PAPPA2 mRNA but this was not reflected at the protein level. Forskolin, TGF-beta and IL-1beta had no significant effect on PAPPA2 mRNA expression. We observed no effects of any treatment on PAPPA or ADAM12 expression. Conclusion: Our study demonstrates that factors previously known to be highly expressed in preeclamptic placentae (PGE2 and TNF-alpha), contribute to the upregulation of PAPPA2. Hypoxia, known to occur in preeclamptic placentae, also increased PAPPA2 expression. These results are consistent with the hypothesis that PAPPA2 is upregulated as a consequence of placental pathology, rather than elevated PAPPA2 levels being a cause of preeclampsia. DOI
29.Christians, JK; Gruslin, A. (2010) Altered levels of insulin-like growth factor binding protein proteases in preeclampsia and intrauterine growth restriction.Prenatal Diagnosis 30: 815-820 Altered levels of insulin-like growth factor binding protein proteases in preeclampsia and intrauterine growth restriction
intrauterine growth restriction; preeclampsia; pregnancy-associated plasma protein-A; ADAM12; IGFBP; insulin-like growth factor
Intrauterine growth restriction (IUGR) and preeclampsia (PE) are leading causes of perinatal and maternal morbidity and mortality. Many studies have found association between low levels of insulin-like growth factor binding protein (IGFBP) proteases in the first trimester maternal circulation and the risk of subsequent development of PE and/or IUGR. These results are generally interpreted to reflect decreased production of the proteases by the placenta, leading to reduced proteolysis of IGFBPs and lower free levels of insulin-like growth factor (IGF), resulting in diminished feto-placental development. However, the association between low circulating levels of placental proteins early in pregnancy and the subsequent development of IUGR and/or PE could be due to low exchange in the placenta and not due to reduced production. In contrast, late in pregnancy, the circulating levels of these proteins and their expression in the placenta are often elevated in PE, which may reflect upregulation to compensate for abnormal placental development, that is an adaptive mechanism to increase IGFBP proteolysis, increase local IGF levels and promote feto-placental growth. Further research into the biological mechanisms underlying these associations will aid the identification of high-risk pregnancies and the development of therapeutic targets for diseases for which there are presently no preventative measures. Copyright (C) 2010 John Wiley & Sons, Ltd. DOI
28. Wagner, PK; Christians, JK. (2010) Altered placental expression of PAPPA2 does not affect birth weight in mice.Reproductive Biology and Endocrinology 8 Altered placental expression of PAPPA2 does not affect birth weight in mice
Background: Pregnancy-associated plasma protein A2 (PAPPA2) is an insulin-like growth factor binding protein (IGFBP) protease expressed in the placenta and upregulated in pregnancies complicated by pre-eclampsia. The mechanism linking PAPPA2 expression and pre-eclampsia and the consequences of altered PAPPA2 expression remain unknown. We previously identified PAPPA2 as a candidate gene for a quantitative trait locus (QTL) affecting growth in mice and in the present study examined whether this QTL affects placental PAPPA2 expression and, in turn, placental or embryonic growth. Methods: Using a line of mice that are genetically homogenous apart from a 1 megabase QTL region containing the PAPPA2 gene, we bred mice homozygous for alternate QTL genotypes and collected and weighed placentae and embryos at E12.5. We used quantitative RT-PCR to measure the mRNA levels of PAPPA2, as well as mRNA levels of IGFBP-5 (PAPPA2's substrate), and PAPPA (a closely related IGFBP protease) to examine potential feedback and compensation effects. Western blotting was used to quantify PAPPA2 protein. Birth weight was measured in pregnancies allowed to proceed to parturition. Results: PAPPA2 mRNA and protein expression levels in the placenta differed by a factor of 2.5 between genotypes, but we did not find a significant difference between genotypes in embryonic PAPPA2 mRNA levels. Placental IGFBP-5 and PAPPA mRNA expression levels were not altered in response to PAPPA2 levels, and we could not detect IGFBP-5 protein in the placenta by Western blotting. The observed difference in placental PAPPA2 expression had no significant effect on placental or embryonic mass at mid-gestation, birth weight or litter size. Conclusions: Despite a significant difference between genotypes in placental PAPPA2 expression similar in magnitude to the difference between pre-eclamptic and normal placentae previously reported, we observed no difference in embryonic, placental or birth weight. Our results suggest that elevated PAPPA2 levels are a consequence, rather than a cause, of pregnancy complications. DOI
27.Christians, JK; Watt, CA. (2009) Mononucleotide repeats represent an important source of polymorphic microsatellite markers in Aspergillus nidulans.Molecular Ecology Resources 9: 572-578 Mononucleotide repeats represent an important source of polymorphic microsatellite markers in Aspergillus nidulans
SIMPLE SEQUENCE REPEATS; SACCHAROMYCES-CEREVISIAE; FUNGAL GENOMES; FUMIGATUS; EPIDEMIOLOGY; NEUROSPORA; ABUNDANCE; MUTATION; STRAINS; LOCI
In fungi, microsatellites occur less frequently throughout the genome and tend to be less polymorphic compared with other organisms. Most studies that develop microsatellites for fungi focus on dinucleotide and trinucleotide repeats, and thus mononucleotide repeats, which are much more abundant in fungal genomes, may represent an overlooked resource. This study examined the relative probabilities of polymorphism in mononucleotide, dinucleotide and trinucleotide repeats in Aspergillus nidulans. As previously found, the probability of polymorphism increased with increasing number of repeating units. Dinucleotide and trinucleotide repeats had higher probabilities of polymorphism than mononucleotide repeats, but this was offset by the presence of numerous long mononucleotide repeats within the genome. Mononucleotide microsatellites with 20 or more repeating units have a probability of polymorphism similar to dinucleotide and trinucleotide microsatellites, and therefore, consideration of mononucleotide repeats will substantially increase the number of potential markers available. DOI
26. Wang, J; Qiu, Q; Haider, M; Bell, M; Gruslin, A; Christians, JK. (2009) Expression of pregnancy-associated plasma protein A2 during pregnancy in human and mouse.Journal of Endocrinology 202: 337-345 Expression of pregnancy-associated plasma protein A2 during pregnancy in human and mouse
INTRAUTERINE GROWTH RESTRICTION; QUANTITATIVE TRAIT LOCUS; FACTOR-BINDING-PROTEIN; SERUM PAPP-A; PROTEOLYTIC ACTIVITY; SEVERE PREECLAMPSIA; GENE-EXPRESSION; 1ST TRIMESTER; IGF-II; PLACENTA
Pregnancy-associated plasma protein-A and -A2 (PAPPA and PAPPA2) are proteases that cleave IGF binding proteins (IGFBPs) and thereby increase the bioavailability of growth factors. PAPPA has long been recognized as a marker of fetal genetic disorders and adverse pregnancy outcomes. In contrast, although PAPPA2 is also highly expressed in human placenta, its physiological importance is not clear. To establish whether mice will be a useful model for the study of PAPPA2, we compared the patterns of expression of PAPPA2 in the placentae of mouse and human. We show, for the first time, that Pappa2 is highly expressed in mouse placenta, as is the case in humans. Specifically, it is expressed at the interface of the maternal and fetal layers of the mouse placenta at all gestational stages studied (10.5-16.5 days post coitum). Similarly, PAPPA2 is expressed in the syncytiotrophoblast layer of human placental villi and is also detected in some invasive extravillous trophoblasts in the first trimester. These results are consistent with a model whereby PAPPA2 cleaves IGFBPs produced in the maternal decidua to promote feto-placental growth, and indicate that this protein may play analogous roles in human and mouse placenta. PAPPA2 protein is detectable in the circulation of pregnant mice and humans during the first trimester and at term, raising the possibility that PAPPA2 may be a useful biomarker of placental dysfunction, Pappa2 expression also shows specific localization within the mouse embryo and therefore may play roles in fetal development, independent of its action in the placenta. journal of Endocrinology (2009) 202, 337-345 DOI
25. Hodgson, ZG; Meddle, SL; Christians, JK; Sperry, TS; Healy, SD. (2008) Influence of sex steroid hormones on spatial memory in a songbird.Journal of Comparative Physiology A-Neuroethology Sensory Neural and Behavioral Physiology 194: 963-969 Influence of sex steroid hormones on spatial memory in a songbird
Androgen receptor; Estrogen receptor; Hippocampus; Memory; Songbird ESTROGEN-RECEPTORS; LUTEINIZING-HORMONE; RAT HIPPOCAMPUS; AVIAN BRAIN; ADULT-RATS; AROMATASE; ANDROGEN; TESTOSTERONE; FOREBRAIN; PASSERINE
In mammals, sex steroid hormones influence spatial learning and memory abilities but there are few data regarding such effects in birds. We investigated whether non-invasive sex steroid hormone treatment would affect spatial memory task performance of great tits (Parus major). For five consecutive days, birds were fed wax moth larvae injected with either 80 mu g testosterone or 80 mu g estradiol carried in peanut oil immediately prior to behavioral testing. During the 5 days prior to and the 5 days following hormone treatment, birds were fed vehicle-injected larvae. Both hormone manipulations resulted in an elevation of circulating hormone levels within 5 min of larva ingestion. This elevation was sustained for at least 30 min but had no short-term (< 1 day) effect on spatial memory performance. However, performance tended to increase during the first 5 days of vehicle treatment and during both sex steroid treatments whereas it decreased during the 5 days of vehicle treatment following either hormone treatment. These results suggest that both hormones led to some improvement in spatial memory that declined once treatment ended. The great tit hippocampus was found to express androgen and estrogen receptors which would provide a direct site of sex steroid action. DOI
24.Christians, JK; Senger, LK. (2007) Fine mapping dissects pleiotropic growth quantitative trait locus into linked loci.Mammalian Genome 18: 240-245 Fine mapping dissects pleiotropic growth quantitative trait locus into linked loci
A recurring issue in studies of quantitative trait loci (QTLs) is whether QTLs that appear to have pleiotropic effects are indeed caused by pleiotropy at single loci or by linked QTLs. Previous work identified a QTL that affected tail length in mice and the lengths of various bones, including the humerus, ulna, femur, tibia, and mandible. The effect of this QTL on tail length has since been found to be due to multiple linked QTLs and so its apparently pleiotropic effects may have been due to linked QTLs with distinct effects. In the present study we examined a line of mice segregating only for a 0.94-Mb chromosomal region known to contain a subset of the QTLs influencing tail length. We measured a number of skeletal dimensions, including the lengths of the skull, mandible, humerus, ulna, femur, tibia, calcaneus, metatarsus, and a tail bone. The QTL region was found to have effects on the size of the mandible and length of the tail bone, with little or no effect on the other traits. Using a randomization approach, we rejected the null hypothesis that the QTL affected all traits equally, thereby demonstrating that the pleiotropic effects reported earlier were due to linked loci with distinct effects. This result underlines the possibility that seemingly pleiotropic effects of QTLs may frequently be due to linked loci and that high-resolution mapping will often be required to distinguish between pleiotropy and linkage.
23. Hansson, B; Jack, L; Christians, JK; Pemberton, JM; Akesson, M; Westerdahl, H; Bensch, S; Hasselquist, D. (2007) No evidence for inbreeding avoidance in a great reed warbler population.Behav Ecol 18: 157-164 No evidence for inbreeding avoidance in a great reed warbler population
dispersal; inbreeding avoidance; inbreeding depression; kin recognition; pedigree; relatedness
Inbreeding depression may drive the evolution of inbreeding avoidance through dispersal and mate choice. In birds, many species show female-biased dispersal, which is an effective inbreeding avoidance mechanism. In contrast, there is scarce evidence in birds for kin discriminative mate choice, which may, at least partly, reflect difficulties detecting it. First, kin discrimination may be realized as dispersal, and this is difficult to distinguish from other causes of dispersal. Second, even within small, isolated populations, it is often difficult to determine the potential candidates available to a female when choosing a mate. We sought evidence for inbreeding avoidance via kin discrimination in a breeding population of great reed warblers (Acrocephalus arundinaceus) studied over 17 years. Inbreeding depression is strong in the population, suggesting that it would be adaptive to avoid relatives as mates. Detailed data on timing of settlement and mate search movements made it possible to identify candidate mates for each female, and long-term pedigrees and resolved parentage enabled us to estimate relatedness between females and their candidate mates. We found no evidence for kin discrimination: mate choice was random with respect to relatedness when all mate-choice events were considered, and, after correction for multiple tests, also in all breeding years. We suggest that dispersal is a sufficient inbreeding avoidance mechanism in most situations, although the lack of kin discriminative mate choice has negative consequences for some females, because they end up mating with closely related males that lowers their fitness.
22.Christians, JK; Hoeflich, A; Keightley, PD. (2006) PAPPA2, an enzyme that cleaves an insulin-like growth-factor-binding protein, is a candidate gene for a quantitative trait locus affecting body size in mice.Genetics 173: 1547-1553 PAPPA2, an enzyme that cleaves an insulin-like growth-factor-binding protein, is a candidate gene for a quantitative trait locus affecting body size in mice
Identifying genes responsible for quantitative variation remains a major challenge. We previously identified a quantitative trait locus (QTL) affecting body size that segregated between two inbred strains of mice. By fine mapping, we have refined the location of this QTL to a genomic region containing only four protein-coding genes. One of these genes, PAPPA2, is a strong candidate because it codes for an enzyme that cleaves insulin-like growth-factor-binding protein 5 (IGFBP-5), an important stimulator of bone formation. Among littermates that segregate only for the four-gene region, we show that the QTL has a significant effect on the circulating levels of IGFBP-5 and IGFBP-3 (the latter subject to limited degradation by PAPPA2), but not on levels of IGFBP-2 and IGFBP-4, which are not cleaved by PAPPA2. There are 14 nonsynonymous SNPs among QTL alleles, which may affect the activity of the translated protein. The refinement of the target region to four genes and the finding that the QTL affects IGFBP-5 levels suggest that PAPPA2 may be involved with normal postnatal growth. Our mapping results also illustrate the potentially fractal nature of QTL: as we mapped our QTL with increasing resolution, what appeared to be a single QTL resolved into three closely linked QTL (previous work), and then one of these was further dissected into two in this study.PDF
20. Oliver, F. , Christians, J.K. , Liu, X, Rhind, S., Verma, V., Davison, C., Brown, S.D.M, Denny, P., and Keightley, P.D. (2005) Regulatory variation at glypican-3 underlies a major growth QTL in mice.PLOS Biology 3: e135. Regulatory variation at glypican-3 underlies a major growth QTL in mice.
The genetic basis of variation in complex traits remains poorly understood, and few genes underlying variation have been identified. Previous work identified a quantitative trait locus (QTL) responsible for much of the response to selection on growth in mice, effecting a change in body mass of approximately 20%. By fine-mapping, we have resolved the location of this QTL to a 660-kb region containing only two genes of known function, Gpc3 and Gpc4, and two other putative genes of unknown function. There are no non-synonymous polymorphisms in any of these genes, indicating that the QTL affects gene regulation. Mice carrying the high-growth QTL allele have approximately 15% lower Gpc3 mRNA expression in kidney and liver, whereas expression differences at Gpc4 are non-significant. Expression profiles of the two other genes within the region are inconsistent with a factor responsible for a general effect on growth. Polymorphisms in the 3' untranslated region of Gpc3 are strong candidates for the causal sequence variation. Gpc3 loss-of-function mutations in humans and mice cause overgrowth and developmental abnormalities. However, no deleterious side-effects were detected in our mice, indicating that genes involved in Mendelian diseases also contribute to complex trait variation. Furthermore, these findings show that small changes in gene expression can have substantial phenotypic effects.PDF
16. Williams, TD; Challenger, WO; Christians, JK; Evanson, M; Love, O; Vezina, F. (2004) What causes the decrease in haematocrit during egg production?Functional Ecology 18: 330-336 What causes the decrease in haematocrit during egg production?
Aerobic performance; cost of reproduction; egg-laying; hematocrit
1. Anaemia has been reported in wild animals, typically associated with traumatic events or ill health. However, female birds routinely become 'anaemic' during egg-laying; we sought to determine the causes of this reduction in haematocrit. 2. Haematocrit in female European Starlings (Sturnus vulgaris Linnaeus) decreased between pre-breeding and egg-laying in 3 out of 4 years (the decrease was marginally non-significant in the fourth year). This was independent of changes in ambient temperature altering the metabolic requirements for thermoregulation. 3. There was a positive relationship between haematocrit and plasma levels of the yolk precursor vitellogenin among egg-laying birds, supporting the hypothesis that the initial reduction in haematocrit is caused by increased blood volume associated with osmoregulatory adjustments to elevated levels of yolk precursors. 4. However, haematocrit did not always recover upon cessation of egg production, remaining low at clutch completion (2 of 4 years), incubation (1 of 2 years) and chick rearing (1 of 4 years), suggesting an additional cause of the prolonged reduction in haematocrit. 5. Given the magnitude and prolonged nature of the changes in haematocrit we report, and the interannual variation in haematocrit even during chick-rearing (47-54%), we suggest that 'anaemia' associated with egg production might have implications for aerobic performance during later stages of breeding.
15.Christians, JK; Bingham, V; Oliver, F; Heath, TT; Keightley, PD. (2003) Characterization of a QTL affecting skeletal size in mice.Mammalian Genome 14: 175-183 Characterization of a QTL affecting skeletal size in mice
Previous work identified a tail length QTL on Chromosome (Chr) 1 in an F-2, population of C57BL/6J x DBA/2J mice. The goals of the present study were to (1) refine the position of this QTL by additional genotyping of samples from the original study; (2) confirm the effect of this QTL by producing a partially congenic strain carrying the C57BL/6J allele against the DBA/2J background; and (3) examine the effect of the QTL on skeletal dimensions. The presence of the QTL was confirmed in a new F-2 population (N = 431) derived from the partially congenic strain, and estimates of its additive effects were similar to those from the original F-2 population (N = 901) in both sexes, i.e., the C57BL/6J chromosomal segment increased tail length, the additive effect (half the difference between homozygotes) being 0.5-0.8 standard deviations. The QTL region was more than halved, relative to that in the previous study, to an 8-cM region between D1Mit30 and D1Mit57. Among a subsample of individuals (N = 30) from the new F-2 population that were not recombinant within the QTL region, there was a significant additive effect of the QTL on the length of the humerus, femur, tibia, mandible, scapula, pelvic girdle, and a tail bone; the direction of the effect was the same as for tail length. No significant effect was found on the number of bones in the tail or on the dimensions of the ulna, skull, or first vertebra. DOI
14. Williams, TD; Christians, JK. (2003) Experimental dissociation of the effects of diet, age and breeding experience on primary reproductive effort in zebra finches Taeniopygia guttata.Journal of Avian Biology 34: 379-386 Experimental dissociation of the effects of diet, age and breeding experience on primary reproductive effort in zebra finches Taeniopygia guttata
Reproductive performance varies with age in a wide range of organisms, and increasingly such patterns are interpreted in terms of state-dependent models. We sought to characterise 'state' with regards to age-related variation in clutch size, egg mass and timing of breeding in captive zebra finches Taeniopygia guttata, focusing on the roles of diet quality, age and breeding experience. Females on a high-quality diet laid larger clutches of larger eggs than did females on a low-quality diet. The effect of age on reproductive performance was examined by comparing females breeding (i.e. paired) for the first time at either 3- and/or 6-months of age. Clutch size increased with age but on the low-quality diet only, not on the high-quality diet. Furthermore, clutch size decreased between 3- and 6-months of age in birds bred first on the high-quality diet and then on the low-quality diet. Age did not affect egg mass but older birds had shorter laying intervals. Reproductive performance did not differ between females breeding at 6-months of age for the first or second time: the effects of age were not due to 'training' effects or experience specific to breeding (e.g. undergoing the physiological process of egg formation). In conclusion, nutritional condition (diet) emerged as a central component of state that could strongly influence, and even reverse, any age-dependent increase in primary reproductive performance.
13.Christians, JK. (2002) Avian egg size: variation within species and inflexibility within individuals.Biological Reviews 77 Avian egg size: variation within species and inflexibility within individuals
age; egg mass; food; intraspecific variation; optimal egg size theory; phenotypic plasticity; physiology; reproductive performance; temperature
DOI
11.Christians, JK; Williams, TD. (2002) Effects of porcine follicle-stimulating hormone on the reproductive performance of female zebra finches (Taeniopygia guttata).General and Comparative Endocrinology 125: 121-131 Effects of porcine follicle-stimulating hormone on the reproductive performance of female zebra finches (Taeniopygia guttata)
FSH; egg production; egg size; clutch size; trade-off; phenotypic engineering
It has been suggested that follicle-stimulating hormone (FSH) may play a role in egg size/number trade-offs in oviparous vertebrates. We tested this hypothesis in an avian species by administering porcine FSH (pFSH) to intact, captive female zebra finches (Taeniopygia guttata) during egg formation. We predicted that (1) pFSH would increase the number of ovarian follicles recruited into rapid yolk development and so increase clutch size, (2) an increase in clutch size would lead to a reduction in egg size, and (3) doses of pFSH that were not sufficient to increase clutch size would increase yolk deposition and so increase egg mass. Although a range of pFSH doses decreased egg mass by ca. 10% in three separate experiments, the reduction in egg mass occurred in the absence of an increase in the number of eggs laid. Porcine FSH decreased mean clutch size significantly in one experiment and reduced median clutch size significantly in the other two experiments. The results of this study did not support the hypothesis that FSH mediates a trade-off between egg size and clutch size in birds. (C) 2002 Elsevier Science (USA).
10. Challenger, WO; Williams, TD; Christians, JK; Vezina, F. (2001) Follicular development and plasma yolk precursor dynamics through the laying cycle in the European starling (Sturnus vulgaris).Physiological and Biochemical Zoology 74: 356-365 Follicular development and plasma yolk precursor dynamics through the laying cycle in the European starling (Sturnus vulgaris)
We investigated the quantitative matching of plasma yolk precursor supply (the plasma pool) to follicle demand during yolk formation in European starlings (Sturnus vulgaris). Plasma concentrations of the two yolk precursors, vitellogenin (VTG) and very low density lipoprotein (VLDL), were only elevated coincident with rapid yolk development (RYD) and matched variation in total yolky follicle mass. VTG and VLDL were low (<0.4 <mu>g/mL and <4.2 mg/mL, respectively) in nonbreeders and prebreeders with no yolky follicles, and at clutch completion. They increased to 4.02 <mu>g/mL and 19.4 mg/mL in birds with a full follicle hierarchy (F-1-F-4), and concentrations then remained high and actually increased up to the point where only a single, yolky (F-1) follicle remained. However, there was some evidence for mismatching of supply and demand: (a) precursor concentrations increased throughout the laying cycle even though the number of developing follicles decreased. We suggest that this is because of a requirement to maintain a large precursor pool to maintain high uptake rates; and (b) in birds with a full follicle hierarchy, precursor concentrations were negatively correlated with total follicle mass. This suggests that high uptake rates in large follicles can actually deplete circulating precursor concentrations. Plasma concentrations of both yolk precursors increased rapidly in the early morning with (predicted) time after ovulation, consistent with a lack of fine control of precursor concentrations. However, mean plasma VTG concentrations did not differ between morning or evening samples. In contrast, plasma VLDL concentrations were lower in the morning (16.8 mg/mL) than in the evening (22.9 mg/mL). Although there is marked individual variation in plasma VTG and VLDL (four- to eightfold), both precursors were repeatable in the short term (24 h), and plasma VTG was repeatable over a 14-d interval between successive breeding attempts.
8.Christians, JK; Williams, TD. (2001) Interindividual variation in yolk mass and the rate of growth of ovarian follicles in the zebra finch (Taeniopygia guttata).Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology 171: 255-261 Interindividual variation in yolk mass and the rate of growth of ovarian follicles in the zebra finch (Taeniopygia guttata)
intraspecific variation; egg size; rapid yolk development; repeatability; vitellogenin
The amount of resources invested in an individual egg yolk must be determined by its rate of growth and/or the duration of growth. We examined interindividual variation in the growth rate of yolks by injecting radiolabeled amino acid into breeding female zebra finches and measuring the activity associated with protein in the yolks of eggs laid subsequently. We predicted that (1) there would be a positive correlation between yolk mass and the rate of uptake of activity into the yolk; and (2) there would be a negative correlation between clutch size and the amount of activity taken up by each of the follicles due to competition between follicles for circulating yolk precursors. The rate of uptake of activity by the yolks was positively related to yolk mass (r(2)=0.24, 0.35 and 0.50 for the yolks of the third-, fourth- and fifth-laid eggs, respectively), suggesting that interindividual variation in yolk mass is due, at least in part, to variation in the rate of follicle growth. However, we found no evidence of a trade-off between yolk size and number. The uptake of activity was generally repeatable between breeding attempts (repeatability = 0.23-0.44), as was mean yolk mass (repeatability = 0.35), suggesting that these traits are characteristics of individual females.
7.Christians, JK; Williams, TD. (2001) Intraspecific variation in reproductive physiology and egg quality in the European Starling Sturnus vulgaris.Journal of Avian Biology 32: 31-37 Intraspecific variation in reproductive physiology and egg quality in the European Starling Sturnus vulgaris
Egg mass shows large intraspecific variation in birds and is repeatable within individuals. The mechanisms underlying this variation are unknown. We hypothesized that measures of egg quality (the mass of yolk protein, yolk lipid, and albumen protein) would be positively correlated with the plasma pools of the yolk precursor vitellogenin, and the masses of the oviduct, metabolic machinery (liver, heart, lungs, kidneys, gizzard, small intestine and pancreas), and endogenous stores of protein and lipid. We tested these predictions in European Starlings Sturnus vulgaris is collected at the peak of egg production effort. In contrast to our predictions, both yolk protein and yolk lipid were negatively correlated with plasma vitellogenin levels. Albumen protein was positively related to oviduct mass, but other aspects of body composition failed to explain variation in egg quality. Hence, while we observed correlations between egg composition and peripheral systems (circulating precursor pools and the oviduct), we found no evidence that egg quality is determined by more general processes, i.e., the supply and processing of nutrients.
3.Christians, JK; Williams, TD. (1999) Organ mass dynamics in relation to yolk precursor production and egg formation in European starlings Sturnus vulgaris.Physiological and Biochemical Zoology 72: 455-461 Organ mass dynamics in relation to yolk precursor production and egg formation in European starlings Sturnus vulgaris
Egg production in passerines and other birds requires rapid synthesis of proteins and lipids. We hypothesized that these biosynthetic demands would necessitate hypertrophy of the liver, which produces the yolk precursors vitellogenin and very low-density Lipoprotein (VLDL), and of the metabolic machinery that supports the liver's biosynthetic activity (e.g., heart, kidneys, lungs, and digestive organs). To test this hypothesis, free-living female European starlings (Sturnus vulgaris) were collected through two breeding seasons. Change in liver mass in relation to breeding stage differed between years, as did the relationship between liver mass and plasma vitellogenin levels. In the first year, dry lean glycogen-free liver mass showed little seasonal variation and was not correlated with vitellogenin levels among egg-laying females. In the second year, liver mass was 4%-44% greater during egg laying than at other stages of breeding and was positively related to vitellogenin levels. In both years, the mass of the liver was not related to plasma VLDL levels. Thus, we did not find consistent relationships between liver mass and its biosynthetic output. In contrast to our hypotheses, the masses of the heart and digestive organs were lower during egg laying than they were before breeding. Meeting the biosynthetic demands of egg production does not appear to require hypertrophy of the liver or supporting metabolic machinery.
2.Christians, JK; Williams, TD. (1999) Effects of exogenous 17 beta-estradiol on tee reproductive physiology and reproductive performance of European starlings (Sturnus vulgaris).Journal of Experimental Biology 202: 2679-2685 Effects of exogenous 17 beta-estradiol on tee reproductive physiology and reproductive performance of European starlings (Sturnus vulgaris)
egg production; yolk; oocyte growth; vitellogenin; intraspecific variation; starling; Sturnus vulgaris
Egg mass shows large intraspecific variation in birds and yet the mechanisms underlying this variation remain unknown. We hypothesized that estradiol would play a central role in determining egg mass, since this hormone stimulates the production of yolk precursors (vitellogenin and very-low density lipoprotein, VLDL) by the liver, and of albumen by the oviduct. We gave European starlings (Sturnus vulgaris) silastic implants containing estradiol prior to egg formation, which we predicted would increase egg mass. As expected, exogenous estradiol stimulated a marked (49 %) increase in plasma vitellogenin levels at the beginning of laying. At clutch completion, plasma VLDL levels and oviduct mass were also elevated in estradiol-treated females compared with controls. However, estradiol had no effect on fresh egg mass or clutch size. Estradiol treatment actually decreased the mass of yolk protein and lipid, perhaps by decreasing the rate of uptake of yolk precursors at the ovary. The failure of estradiol to increase egg mass indicates that this phenotype may be regulated at higher levels of organization (e.g. negative feedback, uptake of yolk precursors) than those studied in this experiment. Despite elevating yolk precursor levels, treatment with estradiol had no effect on the mass of the liver or endogenous stores of protein and lipid at clutch completion.
1. Williams, TD; Christians, JK; Aiken, JJ; Evanson, M. (1999) Enhanced immune function does not depress reproductive output.Proceedings of the Royal Society of London Series B-Biological Sciences 266: 753-757 Enhanced immune function does not depress reproductive output
immune function; reproductive effort; trade-offs
Costs of reproduction might be mediated by a physiological (resource allocation) trade-off between immune function and reproductive effort, and several recent studies have shown that an experimental increase in reproductive effort is associated with decreased immune function. Here we test the complementary prediction of this hypothesis: that increased immune function (specific antibody production) depresses reproductive output. Female European starlings (Sturnus vulgaris) were injected with a nonpathogenic antigen (sheep red blood cells) following completion of laying of their first clutch, to stimulate an in vivo humoral immune response (primary antibody production). We induced laying of a second clutch by removing the first clutch, and assessed changes in reproductive performance in individual females pre- and post-treatment. Injection of sheep red blood cells produced a significant antibody response in 96% (n=29) of treated females, with titres comparable to previous studies (range 1-7). However, increased antibody production did not decrease primary or secondary female reproductive effort (re-laying interval, egg size, clutch size, chick growth or fledging success), compared with control, saline-injected birds (n = 22). These data do not support a simple resource allocation model for the cost of reproduction, based on a reciprocal, negative relationship between resources allocated to immune function and reproduction.
