a, Gene correction frequency in patient-specific iPS cells bearing a mutation (A353V) in the DKC1 gene. b, Immunostaining of gene-corrected and -expanded iPS cells (clones 1–3) showing the expression of pluripotency markers OCT4, NANOG, SSEA-4 and TRA-1–60 (n = 3). c, Representative chromatogram of Sanger sequencing of the parental iPS cell line (DKC1A353V) and a gene-corrected iPS clone (DKC1#2AB3). d, Northern blot radiograph showing TERC, and 18S (loading control) RNA levels in wild-type (WT), DKC1A353V and gene-corrected iPS clone (DKC1#2AB3) cells. e, Southern blot telomere length analysis in WT, DKC1A353V and gene-corrected (DKC1#2AB3) iPS cells. A full blot scan is shown in Supplementary Fig. 4. Pooled data from all the independent experiments are shown with individual data points as grey dots (n = 5). Significance was calculated using paired two-tailed t-test (*P < 0.05). Error bars represent s.e.m. Scale bars: 100 μm. MW, DNA molecular weight ladder.