Based on limited published evidence, SSMEM1 is a testis-specific, serine-rich single-pass membrane protein that functions in spermatogenesis. It binds proteins and is expressed during spermatid development but not in mature sperm. SSMEM1 is essential for male fertility, with knockout mice exhibiting globozoospermia and asthenozoospermia due to abnormal Golgi localization during spermatid development 1. The protein is critical for proper intracellular Golgi movement and spatiotemporal sperm head formation required for fertilization.