For assessing the effect of c.810+1G>T on the POC1B transcript, total RNA was isolated from peripheral-blood cells from the affected person B-II:1 and three control individuals according to the manufacturer’s (QIAGEN) protocol. The peripheral-blood cells of B-II:1 and the control individuals were cultured according to standard procedures with the use of phytohaemagglutinine. The leukocytes of the affected individual were grown for 4–6 hr with or without cycloheximide for visualization of the effect of the mutation and possible degradation of nonsense-containing mRNAs by nonsense-mediated decay.17 With the use of a hypotone osmotic shock and centrifugation, the leucocytes were separated from the erythrocytes. Reverse transcription with iScript (Biorad) was performed on 1 μg of total RNA. RT-PCR experiments were performed with 2.5 μl cDNA with primers in exons 5 and 9 (Table S2) (35 cycles) and were followed by Sanger sequencing using a 3100 or 3730 DNA Analyzer (Applied Biosystems).