CELF3 (CUGBP Elav-like family member 3) is an RNA-binding protein that regulates pre-mRNA alternative splicing and mRNA stability in tissue-specific and developmentally regulated contexts. CELF3 mediates exon inclusion and exclusion events, specifically activating cardiac TNNT2 exon 5 inclusion during heart remodeling and promoting MAPT/Tau exon 10 splicing by binding to muscle-specific splicing enhancer sites 1. The protein forms nuclear bodies (CS bodies) that colocalize with splicing factor SF1, and interacts with the long noncoding RNA Gomafu, which may sequester CELF3 into separate nuclear compartments to modulate splicing regulation 2. CELF3 functions alongside other CELF family members in destabilizing synaptic gene mRNAs through interaction with 3' UTR elements, contributing to post-transcriptional gene regulation in the nervous system 3. Disease relevance includes roles in myotonic dystrophy pathology, where CELF proteins contribute to abnormal CLCN1 chloride channel splicing leading to myotonia 41. CELF3 is also implicated in cancer progression, with differential expression associated with colorectal cancer metastasis 5 and lung cancer progression through interactions with cancer-associated fibroblasts 6. Additionally, CELF3 interacts with schizophrenia-associated proteins in neuronal splicing regulation 7.