The function of ENSG00000203867 (RBM20, RNA binding motif protein 20) is as follows. RNA-binding protein that acts as a regulator of mRNA splicing of a subset of genes encoding key structural proteins involved in cardiac development, such as TTN (Titin), CACNA1C, CAMK2D or PDLIM5/ENH (PubMed:22466703, PubMed:24960161, PubMed:26604136, PubMed:27496873, PubMed:27531932, PubMed:29895960, PubMed:30948719, PubMed:32840935, PubMed:34732726, PubMed:35427468). Acts as a repressor of mRNA splicing: specifically binds the 5'UCUU-3' motif that is predominantly found within intronic sequences of pre-mRNAs, leading to the exclusion of specific exons in target transcripts (PubMed:24960161, PubMed:30948719, PubMed:34732726). RBM20-mediated exon skipping is hormone-dependent and is essential for TTN isoform transition in both cardiac and skeletal muscles (PubMed:27531932, PubMed:30948719). RBM20- mediated exon skipping of TTN provides substrates for the formation of circular RNA (circRNAs) from the TTN transcripts (PubMed:27531932, PubMed:34732726). Together with RBM24, promotes the expression of short isoforms of PDLIM5/ENH in cardiomyocytes (By similarity). {ECO:0000250|UniProtKB:E9PT37, ECO:0000269|PubMed:22466703, ECO:0000269|PubMed:24960161, ECO:0000269|PubMed:26604136, ECO:0000269|PubMed:27496873, ECO:0000269|PubMed:27531932, ECO:0000269|PubMed:29895960, ECO:0000269|PubMed:30948719, ECO:0000269|PubMed:32840935, ECO:0000269|PubMed:34732726, ECO:0000269|PubMed:35427468}.