Temporally regulated transcription and translation of several testis-specific genes is required to initiate the series of molecular and morphological changes in the male germ cell lineage necessary for the formation of mature spermatozoa. This gene is a member of the SPANX family of cancer/testis-associated genes, which are located in a cluster on chromosome X. The SPANX genes encode differentially expressed testis-specific proteins that localize to various subcellular compartments. This particular gene encodes a sperm protein that is associated with the nucleus but, although a role in spermatogenesis is suggested, the specific function of this family member has not yet been determined. (provided by RefSeq) .