Expression profile of telomerase deficient iPSC

Critically short telomeres activate p53-mediated apoptosis, resulting in organ failure and causing malignant transformation. Mutations in genes responsible for telomere maintenance are linked to a number of specific human diseases. We derived induced pluripotent stem cells (iPSCs) from patients with mutations in the TERT and TERC telomerase genes. Telomerase-mutant iPSCs elongated telomeres, but at a lower rate than healthy iPSCs, and the magnitude of the elongation deficit correlated with the specific mutations impact on telomerase activity. However, elongation significantly varied among iPSC clones harboring the same mutation, and was affected by genetic and environmental factors. iPSCs cultured in hypoxia showed increased telomere length. Potential influence of residual expression of reprogramming factors on telomerase regulation and telomere length was ruled out by excising the transgenes after successful reprogramming. Evidence for telomerase-independent telomere elongation was not observed in these cells. We demonstrate that telomerase is required for telomere elongation in iPSCs and uncover heterogeneity in telomere maintenance even between clones derived from individual patients or siblings with the same mutation, indicating that telomere phenotype may be influenced by acquired and environmental agents. Our data underscore the necessity of studying multiple clones when using iPSCs to model disease. The exon array were done to validate the pluripotent phenotype of the derived normal and telomerase mutant iPSC and to potentially identify differentially expressed genes in mutant iPSC.

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Winkler T, Hong SG, Decker JE, Morgan MJ, Wu C, Hughes WM 5th, Yang Y, Wangsa D, Padilla-Nash HM, Ried T, Young NS, Dunbar CE, Calado RT