Plays a role in spermatogenesis (PubMed:28905369). When overexpressed, prevents nuclear localization of HIF1A (By similarity). Interacts with HIF1A. In mature spermatozoa, localizes to the centriole and midpiece (PubMed:28905369). The 27-kDa peptide associates with the fibrous sheath in mature spermatozoa and localizes to the principal piece of sperm tail, while the 55-kDa peptide localizes to the midpiece (By similarity). Detected in the cytoplasm of almost all spermatogonial cells within the seminiferous tubules (By similarity). Expressed in the testis, in spermatozoa (at protein level) (PubMed:11179690, PubMed:28905369). Expressed in actively dividing fetal tissues, including sternum, intestine, limb, kidney and stomach (PubMed:14585816). Processed into N-terminal 27-kDa and C-terminal 55-kDa fragments. The disease is caused by variants affecting the gene represented in this entry. Belongs to the CEP135/TSGA10 family.