MEIOB is a meiosis-specific single-stranded DNA-binding protein essential for homologous recombination during gametogenesis. Structurally, MEIOB contains an OB-fold domain with a nuclear localization signal (NLS) that requires interaction with its binding partner SPATA22 for proper nuclear localization 1. Functionally, MEIOB stabilizes RAD51 and DMC1 recombinase proteins on DNA, maintaining proper focus numbers after the zygotene stage and promoting faithful synapsis and crossover formation during meiosis I 2. The protein displays dosage-dependent effects, with reduced MEIOB levels correlating directly with meiotic defect severity 2. Mutations in MEIOB cause severe reproductive consequences. Pathogenic variants—including frameshift deletions, nonsense mutations, and splicing defects—result in protein truncation or degradation, impairing MEIOB-SPATA22 interaction and ssDNA binding 34. In males, MEIOB mutations cause non-obstructive azoospermia (NOA) with meiotic arrest and absence of spermatids 54, while all NOA patients with meiotic gene defects showed unsuccessful sperm retrieval 5. In females, MEIOB mutations contribute to premature ovarian insufficiency (POI) 6 and androgenetic hydatidiform moles through meiosis I defects 7. These findings establish MEIOB mutations as clinically significant causes of human infertility warranting genetic screening 8.