RG7834 treatment rescues telomerase activity, increases telomere length, and improves hematopoietic specification in DKC1_A353V mutant hESCs. (A) Quantification of oligo(A) reads at the 3′ end (UGC) of TERC in indicated conditions (average ± standard deviation from 2 independent replicates). TERC reads with more than 2 As at the 3′ end are considered oligoadenylated. (B) Quantification of TERC and TERT by quantitative reverse transcription polymerase chain reaction in DKC1_A353V hESCs treated with DMSO or different concentrations of RG7834 for 30 days (n = 3; biological replicates). (C) Telomerase activity by telomere repeat amplification in DKC1_A353V hESCs treated with DMSO or different concentrations of RG7834. Range of protein concentrations represent fourfold serial dilutions. (D) Telomere length analysis by telomere restriction fragment analysis of DKC1_A353V hESCs treated with DMSO or different concentrations of RG7834 for 90 days. (E) Representative flow cytometric analysis of CD34 and CD43 expression on day 8 of definitive hematopoietic differentiation, following CHIR99021 and SB-431542 treatment in DKC1_A353V cells treated with DMSO or different concentrations of RG7834. (F) Quantification of CD34⁺CD43^– population obtained from day 8 differentiation cultures treated with CHIR99021 and SB-431542, as in panel E. (G) CFC potential of definitive hematopoietic progenitors in WT and DKC1_A353V cells treated with DMSO or 1μM of RG7834 (n = 3; biological replicates). Statistical significance was determined by using one- or two-way analysis of variance following a Bonferroni multiple comparison posttest. *P < .05; **P < .01; ***P < .001. BFU-E, burst forming unit-erythroid; CFC, colony forming cell; MTL, mean telomere length; n.s., not significant.