RBM46 (RNA binding motif protein 46) is an essential RNA-binding protein that regulates the mitotic-to-meiotic transition during spermatogenesis 1. RBM46 functions as a critical component of the YTHDC2/MEIOC complex, where it recognizes and binds to specific GCCUAU/GUUCGA motifs within the 3' UTRs of mitotic transcripts positioned near YTHDC2 U-rich binding sites 1. This binding targets mitotic mRNAs—including transcriptional repressors E2f6 and Mga—for degradation, thereby derepressing meiosis-associated genes and conferring molecular competence for meiotic initiation in response to retinoic acid signaling 2. RBM46 is also required for spermatogonial differentiation and normal synaptonemal complex formation by positively regulating translation of meiotic cohesin subunit mRNAs 1. Testis-specific Rbm46 knockout in mice causes infertility with defective meiotic entry, phenocopying Ythdc2 or Meioc knockouts 1. Dysregulated RBM46 expression is associated with human male fertility disorders 1. Beyond reproduction, RBM46 functions as a novel cofactor for APOBEC1-mediated C-to-U RNA editing, facilitating post-transcriptional modifications involved in diverse cellular processes 3. Environmental toxins such as short-chain chlorinated paraffins impair spermatogenesis partly through suppressing Rbm46 expression via epigenetic mechanisms 4.