Characterization of a novel gene, sperm-tail-associated protein (Stap), in mouse post-meiotic testicular germ cells

During mammalian spermatogenesis, many specific molecules show the dynamics of expression and elimination, corresponding with the morphological differentiation of germ cells. We have isolated a novel cDNA designated F77 from mouse testis by cDNA subtractive hybridization between normal and sterile mice, using the C57BL/6 congenic strain for the hybrid sterilityhyphen;3 lpar;Hsthyphen;3rpar; allele from Mus spretus. The full-length F77 mRNA was 3.4 kb and showed significant nonmatching with entries in the databases. F77 was mapped at a proximal position between D8Mit212 and D8Mit138 on mouse chromosome 8, in which no corresponding genes related to its nucleotide sequence were found. F77 mRNA was not detected in any other organs except the testis of adult fertile mice. F77 protein was only seen in normal adult testis and epididymis. In contrast to normal C57BL/6 mice, F77 mRNA and protein were not seen in germ cell-deficient Kit(W)/Kit(Wv) mice. By in situ hybridization, F77 mRNA was detected mainly at round spermatids in the sexually mature testis, and immunohistochemical analysis revealed that F77 protein was located at the tail of elongated spermatids. We are proposing the name, sperm-tail-associated protein (Stap), for the gene encoding F77 cDNA. Mol. Reprod. Dev. 59: 350-358, 2001.