Nuclear matrix in developing rat spermatogenic cells

The nonchromatin structure or nuclear matrix in developing spermatogenic ce lls of the rat was studied using a biochemical fractionation in concert wit h resinless section electron microscopy. Observations demonstrated that the nuclear matrix of spermatogenic cells consisted of a three-dimensional net work of filaments of variable thicknesses. In spermatagonia and spermatocyt es the nuclear matrix consisted of relatively thin filaments, while that of round spermatids consisted of a thicker interconnecting network of filamen t. In elongating spermatids, the interior of the nuclear matrix consisted o f a network of dense filaments bounded by a peripheral lamina. The protein composition of the nuclear matrix in spermatogenic cells was examined by hi gh-resolution two-dimensional gel electrophoresis and correlated with morph ological changes characteristic of each stage. The results showed that the proteins of nuclear matrix changed in a cell stage-specific manner. These s tage-specific changes corresponded to the major transitions of chromatin st ructure and function during spermatogenesis. Furthermore, immunocytochemica l and immunoblotting analysis of DNA topoisomerase II (topo II) revealed th at this enzyme exhibited stage-specific variations and was associated with the nuclear matrix. These results suggest that the nuclear matrix in sperma togenic cells may be involved in mediating DNA modifications and maintainin g nuclear organization during spermatogenesis. (C) 2001 Wiley-Liss, Inc.