This gene represents one of several duplicated family members that are located on the X chromosome. This gene family encodes proteins that play a role in spermiogenesis. These proteins represent a specific subgroup of cancer/testis-associated antigens, and they may be candidates for tumor vaccines. This family member belongs to a subgroup of related genes that are present in all primates and rats and mice, and thus, it represents one of the ancestral family members. [provided by RefSeq, Sep 2009]