Abstract

It has been previously reported that adult male mice lacking the cell cycle regulator p27 encoded by the Cdkn1b gene display enlarged testes, however, histological examinations of the testes did not show structural abnormal-lities except for remarkable hyperplasia. In the present work testes of p27-knockout mice were studied at the ultrastructural level. Increased numbers of Sertoli cells and several abnormal-lities in the different stages of spermatoge-nesis, such as an increase in the number of spermatogonia were observed. Abnormal transformation of round spermatids into testicular spermatozoa was also observed. Mutant spermatids exhibited certain signs of degeneration where the nuclei contained relatively sparse chromatin and displayed disrupted nuclear envelope, and the mitochondria appeared as empty vesicles with disintegrated cristae. Multinucleated giant cells were formed by cell fusion of some spermatids. Moreover, maturation arrest at spermatid stages was observed. Leydig cells also exhibited various alterations in the nuclear and cytoplasmic components. It is suggested that p 27 may have a regulatory role in the process of spermatogenesis in the adult mouse testis.

Key words: Testis, p 27-knockout mice, ultrastructure, Sertoli cells, spermiogenesis