MEIOSIN is a DNA-binding transcriptional regulator that serves as the primary gatekeeper of meiotic initiation in both male and female germ cells 1. In complex with STRA8, MEIOSIN directly activates transcription of critical meiotic genes to orchestrate the cell-cycle switch from mitosis to meiosis 2. MEIOSIN operates downstream of retinoic acid signaling and acts at the G1/S phase transition to establish the meiotic prophase program, characterized by chromosome 19 and homolog synapsis 13. In spermatogenic cells, mRNA destabilization mediated by MEIOC-YTHDC2-RBM46 enhances cellular competence for MEIOSIN activation by derepressing meiosis-associated genes including Meiosin itself 4. Similarly, during oogenesis, MEIOC promotes meiotic entry by increasing MEIOSIN transcript abundance 5. Loss-of-function variants in MEIOSIN are associated with premature ovarian insufficiency (POI), a major cause of female infertility 6. Functionally, MEIOSIN missense variants can impair transcriptional activation of meiotic genes and disrupt nuclear localization through the HMG box domain, accelerating oocyte depletion 7. Additionally, MEIOSIN downregulation impairs spermatogenesis in response to environmental stressors 8. These findings establish MEIOSIN as essential for reproductive competence in both sexes.