Factor-induced Reprogramming and Zinc Finger Nuclease-aided Gene Targeting Cause Different Genome Instability in -Thalassemia Induced Pluripotent Stem Cells (iPSCs)


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Authors: Ma, N; Shan, YL; Liao, BJ; Kong, GY; Wang, C; Huang, K; Zhang, H; Cai, XJ; Chen, SB; Pei, DQ; Chen, NS; Pan, GJ
Year: 2015
Journal: Journal of Biological Chemistry 290: 12079-12089   Article Link (DOI)
Title: Factor-induced Reprogramming and Zinc Finger Nuclease-aided Gene Targeting Cause Different Genome Instability in -Thalassemia Induced Pluripotent Stem Cells (iPSCs)
Abstract: Background: Genome alterations need to be investigated before clinical application of iPS cells. Results: Reprogramming and gene targeting can generate substantial but different genomic variations. Conclusion: Stringent genomic monitoring and selection are needed both at the time of iPSC derivation and after gene targeting. Significance: This study examined the genome instability during iPSC generation and subsequent gene correction and revealed different genome alterations at each step. The generation of personalized induced pluripotent stem cells (iPSCs) followed by targeted genome editing provides an opportunity for developing customized effective cellular therapies for genetic disorders. However, it is critical to ascertain whether edited iPSCs harbor unfavorable genomic variations before their clinical application. To examine the mutation status of the edited iPSC genome and trace the origin of possible mutations at different steps, we have generated virus-free iPSCs from amniotic cells carrying homozygous point mutations in -hemoglobin gene (HBB) that cause severe -thalassemia (-Thal), corrected the mutations in both HBB alleles by zinc finger nuclease-aided gene targeting, and obtained the final HBB gene-corrected iPSCs by excising the exogenous drug resistance gene with Cre recombinase. Through comparative genomic hybridization and whole-exome sequencing, we uncovered seven copy number variations, five small insertions/deletions, and 64 single nucleotide variations (SNVs) in -Thal iPSCs before the gene targeting step and found a single small copy number variation, 19 insertions/deletions, and 340 single nucleotide variations in the final gene-corrected -Thal iPSCs. Our data revealed that substantial but different genomic variations occurred at factor-induced somatic cell reprogramming and zinc finger nuclease-aided gene targeting steps, suggesting that stringent genomic monitoring and selection are needed both at the time of iPSC derivation and after gene targeting.
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