Electrophoretic pattern of polypeptide synthesis in spermatocytes and spermatids of the mouse.

The pattern of protein synthesis in different stages of spermatogenesis was examined using two-dimensional polyacrylamide gel electrophoresis followed fluorography. The [3H]leucine labelling was performed by incubating in culture either seminiferous tubules before cell separation or isolated germ cells after fractionation by velocity sedimentation at unit gravity in an albumin gradient. The patterns of soluble polypeptides synthesised in middle-late pachytene spermatocytes, round spermatides (steps 1--8 of spermiogenesis) and intermediate spermatids (steps 9--13) have been compared with each other. Approximately 250 fluorographic spots were detected in middle-late pachytene spermatocytes and round spermatids, but only 100 in intermediate spermatids. From the analysis of fluorograms in the three cell stages examined, 5 categories of labelled polypeptides can be identified: (1) those specific of each cell stage; (2) those present in pachytene spermatocytes and early spermatids but absent in intermediate spermatids; (3) polypeptides labelled during spermiogenesis but unlabelled in meiotic cells; (4) polypeptides showing quantitative differences among the three cell types; and finally (5) polypeptides common to the three cell stages. These results are discussed in relation to differential gene expression during spermatogenesis.