Multifunctional RNA-binding protein involved in the regulation of pre-mRNA splicing, mRNA stability and mRNA translation important for cell fate decision and differentiation. Plays a major role in pre-mRNA alternative splicing regulation. Mediates preferentially muscle-specific exon inclusion in numerous mRNAs important for striated cardiac and skeletal muscle cell differentiation. Binds to intronic splicing enhancer (ISE) composed of stretches of GU-rich motifs localized in flanking intron of exon that will be included by alternative splicing. Involved in embryonic stem cell (ESC) transition to cardiac cell differentiation by promoting pre-mRNA alternative splicing events of several pluripotency and/or differentiation genes. Plays a role in the regulation of mRNA stability and mRNA translation to which it is bound. Involved in myogenic differentiation by regulating myog levels. Binds to a huge amount of mRNAs (By similarity). Required for embryonic heart development, sarcomer and M-band formation in striated muscles (PubMed:22345307). Expressed in the embryo from 2 to 72 hours post-fertilization (hpf) (PubMed:22345307). Expressed in the embryonic heart and somites at 14, 20 and 24 hpf (PubMed:22345307). Expressed in myocardial progenitors from 18 to 24 hpf (PubMed:22345307). Expressed in the otic vesicle at 14 hpf (PubMed:22345307). The RRM domain is necessary for mRNA stability and mRNA translation regulation. Morpholino knockdown of the protein leads to death at 6 days post-fertilization (dpf) due to heart growth defects and absence of blood circulation, despite the presence of a beating heart (PubMed:22345307). Show reduced heart contractility from 30 hours post-fertilization (hpf), onwards (PubMed:22345307). Display defects in sarcomere organization from 33 hpf, onwards (PubMed:22345307). Show altered expression of key genes necessary for sarcomere formation (PubMed:22345307).