TRANSCRIPTS EXPRESSED DURING EARLY MOUSE SPERMATOGENESIS

In order to understand the mechanisms that underpin gonadal development, we have conducted a subtractive screen to identify transcripts expressed differentially during the sex-determining period. Suppression subtractive hybridization PCR was performed on cDNA derived from 12.5 dpc male and female gonadal ridges. Clones were tested for differential expression by RNA whole mount in situ hybridization. Those localizing to testis cords were further tested on germ cell-depleted testes, and we examined the pattern of expression of four clones with male germ cell dependent expression by in situ hybridization in postnatal mouse testes. Four clones showed germ cell dependent expression during sex determining period, and we examined their pattern of expression in postnatal mouse testes by in situ hybridization. One of these, K1, encodes a protein closely related to the kinesin-like protein, KIF2. At the onset of spermatogenesis, the transcript signal was intense in the gonocyte cytoplasm and weak in Sertoli cells. This continued until the first onset of meiosis when the signal gradually shifted from spermatogonia to spermatocytes and then to spermatids; the Sertoli cell signal disappeared entirely during the first wave of spermatogenesis. The other three clones, H21 (encoding ADP-ribose polymerase), K22 (cleavage & polyadenylation specificity factor 1) and A12 (KIAA0890) were recognized in gonocytes and Sertoli cells with strong intensity at the onset of spermatogenesis. Although the signals persisted in germ cells throughout the first wave of spermatogenesis and into adulthood, the Sertoli cell signals were lost. In adult testis, all three mRNAs were detected in spermatogonia and spermatocytes. This is the first report that demonstrates the highly regulated expression of these male germ cell dependent gene products in both somatic and germ cells throughout testis development and in adulthood. (poster)