Impact of iPSC cell density on expression of <i>TERT</i> splice variants.

A) Representative phase contrast micrograph, 24 hours after seeding. The number of seeded iPSCs are indicated. Scale bar for image is 1000 μm. B and C) TERT gene expression is shifted from alternatively spliced, exons 7/8 excluding TERT (minus beta), to exons 7/8 including TERT (potential FL) with higher iPSCs density (determined by ddPCR; n = 4 biological replicates per condition). Transcript copies per 1 ng RNA input (B) and splicing ratio (C) were quantified. D) Telomerase activity significantly increased with higher iPSC density compared to lowest cell density condition (determined by ddTRAP; n = 4 biological replicates per condition). One-way ANOVA was performed to compare total amount of TERT including/excluding exons 7/8 (B), ratio of exons 7/8 including TERT splice variants (C), and telomerase activity (D) of all conditions (****, P < 0.0001). Data are presented as means ± standard deviations where applicable.