The function of Ensembl gene identifier ENSG00000152601 (MBNL1, muscleblind like splicing regulator 1) is as follows. Mediates pre-mRNA alternative splicing regulation. Acts either as activator or repressor of splicing on specific pre-mRNA targets. Inhibits cardiac troponin-T (TNNT2) pre-mRNA exon inclusion but induces insulin receptor (IR) pre-mRNA exon inclusion in muscle. Antagonizes the alternative splicing activity pattern of CELF proteins. Regulates the TNNT2 exon 5 skipping through competition with U2AF2. Inhibits the formation of the spliceosome A complex on intron 4 of TNNT2 pre-mRNA. Binds to the stem-loop structure within the polypyrimidine tract of TNNT2 intron 4 during spliceosome assembly. Binds to the 5'-YGCU(U/G)Y-3'consensus sequence. Binds to the IR RNA. Binds to expanded CUG repeat RNA, which folds into a hairpin structure containing GC base pairs and bulged, unpaired U residues. Together with RNA binding proteins RBPMS and RBFOX2, activates vascular smooth muscle cells alternative splicing events (PubMed:37548402). Regulates NCOR2 alternative splicing (By similarity). {ECO:0000250|UniProtKB:A0A8I6B1J2, ECO:0000269|PubMed:10970838, ECO:0000269|PubMed:15257297, ECO:0000269|PubMed:16946708, ECO:0000269|PubMed:18335541, ECO:0000269|PubMed:19470458, ECO:0000269|PubMed:37548402}.