TMPRSS12 is a testis-specific transmembrane serine protease essential for male fertility in mammals 1. Primary function: TMPRSS12 localizes to the acrosomal region of spermatozoa and functions in sperm maturation during epididymal migration 1. Mechanism: TMPRSS12 regulates sperm motility through proteolytic processing of ADAM3, a membrane protein critical for sperm-oviduct migration 1. Knockout mice exhibit normal spermatogenesis but produce immotile sperm unable to migrate from the uterus to the oviduct, resulting in male sterility despite normal sperm morphology 1. Disease relevance: TMPRSS12 disruption may explain genetic cases of idiopathic male infertility 1. The protease is also expressed in testicular cancer/testis antigen contexts and associates with cancer-related genetic variants 2. Additionally, TMPRSS12 is expressed on spermatozoa alongside other viral entry proteases (including TMPRSS2), raising theoretical concerns about COVID-19 susceptibility in reproductive tissues 3. Clinical significance: TMPRSS12 and its downstream signaling cascade represent novel targets for male contraceptive development 1, though human TMPRSS12 exhibits functional divergence from mouse orthologs that complicates translational modeling 4.