RNA Extraction and Splicing Profiling

RNA was extracted using standard Trizol RNA extraction. cDNA was synthesized from 500 ng total RNA in a 10 μl reaction, using Superscript VILO cDNA synthesis kit (Invitrogen) following manufacturer’s instructions. Splicing profiles were monitored by PCR using primers in flanking exons. For each PCR, 1 μl diluted cDNA (1/8) was used as template in a 10 μl PCR reaction using Phusion High-Fidelity PCR Kit (NEB, UK) following manufacturer’s instructions. Splicing profiles were monitored and quantified using the Qiaxcel capillary electrophoresis system (Qiagen) and PSI was calculated as described previously18 (link). All primers used for splicing assays are provided in Supplementary Data 3.