In mice, the interspecific or intersubspecific hybrid sterility has been occasionally found in matings between laboratory mice and wild mice induced by Hybrid sterility (Hst) genes. One of them, Hst3, which controls the sterility of interspecific hybrids between laboratory mice and Mus spretus originated from Spanish wild mouse, is associated with X-Y chromosome dissociation accompanied by spermatogenic breakdown after metaphase I (MI). For detaild analysis of hybrid sterility caused by Hst3, C57BL/6 congenic mice, carring Hst3 derived from spretus, were created.
Up to postnatal day 12, spermatogenesis progressed relatively normal in both type testis. At day 14, when early pachytene spermatocytes appeared in nomal testis, many degenerations weredetected on these cells in sterile testis. At day 20, many round spermatids appeared in nomal testis, while no round spermatids were found in stertile testis. At day 60 of sexually matured age, nomal testis involved in all kinds of germ cells, ho
wever it was noted that few spermatids and spermatozoa were found in sterile testis throughout the histological sections.
According to morphologial differeces between normal and sterile testis, the subtraction method between normal and sterile testis cDNA was performed using congenic mouse testis to analyze the normal spermatogenesis-associated genes. Transcripts of some subtracted cDNA clones were expressed higher in normal testis than in sterile testis by northern blot analysis. One of them, clone F77, showing significant unmatchies with entries in the demonstrated remarkable expression of apporoximately 4kb transcript in nomal testis, compared to those in sterile testis. Additionaly the transcript was not detected at any other organs except testis. Northern blot analysis using developing normal testis and germ cell-defficient W/Wv mutant testis, show that the transcript of cDNA clone F77 was expressed only in normal adult testis, in which it was detected in elongated spermatids and partially round spermatids by in situ hybridization. cDNA clone F77 was mapped at position between Mt-1 and Ctrb on mouse chromosome 8, in which no related genes were detected Less