Expression of p63 and Notch system in the rat testis and vaso-epididymal system during postnatal development
T Hayashi, R Ohno, N Ishii, T Matsuda, T Terao, M Morozumi & T Yamada
The testis and epididymis collaborate in the male gamete development. The testis has the specific function to generate spermatozoa and spermatozoa undergo numerous changes passing through the epididymis. p63 in the basal layer of epithelium plays a key role in maintaining cellular populations, whereas Notch 1 and its ligand Jagged 2 have an important role in the cell differentiation and Jagged 2 is up-regulated by TAp63, which transactivates p53 target genes and induces apoptosis. However, the role of p63 and its relationship with Notch system in the testis have not been examined. Therefore, we investigated the postnatal expression of p63, Jagged 2 and Notch 1 in the testis in comparison with the vaso-epididymal epithelium by Northern blot analysis and immunohistochemistry. In the testis, TAp63 mRNA expression increased at day 14 after birth and the expressions of Jagged 2 and Notch 1 mRNAs increased at day 16, whereas p63 protein was detectable in spermatocytes and Jagged 2 and Notch 1 proteins were in spermatids, suggesting TAp63-mediated Jagged 2 induction activates the Notch system. On the other hand, deltaNp63 mRNA expression was already recognized in the vas deferens at day 0 and advanced chronologically along the duct to the caput epididymis, whereas Jagged 2 and Notch 1 mRNAs were maintained at a low level. The current study has identified that testis and vaso-epididymal system express different p63 isoforms. Moreover, our data raises the probabilities that TAp63 has an important role for maintenance of germ cell numbers, triggering or balancing the development, differentiation and apoptosis of germ cells by activating both Notch system and p53 target genes, and that the chronological differences of deltaNp63 expression result in the morphological and functional differences in the mesonephric tubule.