Developmental expression of c-kit protooncogene in the rat testis

In this study very pure type A spermatogonia, pachytene spermatocytes, round sper-matids and Sertoli cells from rat testis were successfully isolated. The expression of the c-kit receptor,a specific receptor for kit ligand (stem cell factor, steel factor), in these four kinds of cells was exam-ined by northern blot- The synthesis of the c-kit receptor by the spermatogonia was established by hy-bridization of total RNA with a specific cDNA for mouse c-kit receptor. Two mRNA transcripts migrat-ing at 4. 8 kb and 12kb were observed. A faint hybridization signal of 12kb transcript could be observed only in pachytene spermatocytes and round spermatids. In contrast, the Sertoli cells did not express c-kit receptor.In order to study the role of c-kit in spermatogenesis in the rat, the pattern of expression of c-kit in testes during the postnatal period was also investigated. Interestingly, the tissue of testis in rat also ex-pressed the same 2 species of mRNA migrating at 4. 8 kb and 12 kb. The testis of adult rat only ex-pressed the 4. 8 kb transcript, but did not expressed 12 kb transcript.These results indicated that the expression of c-kit receptor mainly originated from type A sper-matogonia. The c-kit receptor can be viewed as a marker of type A spermatogonia. After birth, the ex-pression of these rat testis mRNA transcripts that encode for c-kit is differentially regulated. Further-more, the presence of the 4. 8 kb transcript alone in the adult testis suggests that the 12 kb transcript may play a specific role in germ cell differentiation in immature rats.