The splicing defect in 4.1R Coimbra.

The G→A substitution precludes the splicing at the exon 20 donor splice site and partly activates an internal cryptic site 10 NTs downstream of the acceptor site. This splicing alteration leads to the production of CO.1 and CO.2 isoforms, with a partial and a total skipping of exon 20, respectively. CO.1 would possibly encode an out-of-frame C-terminal amino acid sequence. The predicted amino acid sequences of the truncated C-terminals are aligned to the wild-type sequence at the bottom.