MEIG1 (meiosis/spermiogenesis associated 1) is essential for male fertility, functioning primarily in sperm flagella formation and chr10 remodeling. Mechanistically, MEIG1 localizes to the manchette—a unique structure in elongating spermatids—where it acts as a key organizing protein for intraflagellar transport (IFT) components 1. MEIG1 forms a critical complex with PACRG (Parkin co-regulated gene protein) to enable cargo transport necessary for sperm flagella assembly 2. The MEIG1-PACRG interaction involves specific amino acid residues (Y68 and W50) that mediate protein-protein binding and recruits cargo proteins like SPAG16L to the manchette 2. Beyond spermatogenesis, MEIG1 participates in sperm chr10 remodeling by facilitating histone-to-protamine replacement, a process critical for proper embryo development 3. Disease relevance is substantial: MEIG1 knockout mice are completely infertile with severely reduced sperm counts and impaired embryogenesis due to sperm DNA damage 3. Polymorphisms in MEIG1 (rs150031795) correlate with reduced sperm motility in idiopathic male infertility 4. Clinically, the MEIG1-PACRG complex represents a promising therapeutic target; disrupting this interaction through small molecule inhibitors shows potential for non-hormonal male contraception 5, 6.