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 maps to
chromosome X in a head-to-tail orientation with SPANX family member
B1 and appears to be a duplication of that locus. The SPANXB genes
are unique members of this gene family, since they contain an
additional 18 nt in their coding region compared to the majority of
family members. Although the protein encoded by this gene contains
consensus nuclear localization signals, the major site for
subcellular localization of expressed protein is in the cytoplasmic
droplets of ejaculated spermatozoa. This protein provides a
biochemical marker for studying the unique structures in
spermatazoa, while attempting to further define its role in
spermatogenesis.
