SEMG2 encodes semenogelin 2, a major structural protein in human seminal plasma that participates in forming the gel matrix (sperm coagulum) containing ejaculated spermatozoa and accessory gland secretions 1. The protein functions through interactions with glycolytic enzymes and participates in sperm capacitation and antibacterial responses [GO annotations cited in abstracts]. SEMG2 is subject to strong adaptive evolution, with evidence of positive selection across human populations, particularly affecting reproductive and immune functions 2. The gene shows striking molecular variation across primate species, correlating with differences in sperm competition and mating systems 13. Clinically, SEMG2 has emerged as a cancer-testis antigen frequently re-expressed in multiple malignancies including lung, prostate, and renal cancers 4. Aberrant SEMG2 expression enhances cancer cell energy metabolism by upregulating glycolytic enzymes PKM2 and LDHA, increasing mitochondrial potential and glycolysis 4. In fertility contexts, SEMG2 underexpression associates with primary male infertility, suggesting its diagnostic potential as a seminal plasma biomarker 5. Additionally, SEMG2 appears as a common proteomic signature in urogenital diseases involving renal function 6. These findings indicate SEMG2 functions beyond reproduction in cancer metabolism and fertility assessment.