Telomere lengths of patients and telomerase activity of selected variants. (A) Telomere lengths were measured by MM-qPCR and expressed as a T:S ratio for probands and 99 normal controls. Percentiles for the normal controls are indicated. All samples were normalized to a reference. (B) Telomerase activity was measured in WI38-VA13 cells ectopically expressing the stated telomerase variant. Activity was calculated as a percentage of wild-type levels, measured using the TRAP. Less than 5% activity is considered LOF. RT-PCR products demonstrate expression of wild-type and mutant TERC and TERT mRNA. Bars show standard error of mean of duplicate readings from 2 independent experiments. MM-qPCR, monochrome multiplex quantitative PCR; mRNA, messenger RNA; NTC, no template control; RT-PCR, reverse transcription PCR.