EXPRESSION AND LOCALIZATION OF DNA TOPOISOMERASE-II DURING RAT SPERMATOGENESIS

The potential role(s) of DNA topoisomerase II (topo II) during chromat in changes that characterize different stages of spermatogenesis was i nvestigated in the rat by an analysis of the expression and localizati on of topo II mRNA and protein in individual spermatogenic cells. Expr ession of topo II was restricted to spermatogonia, spermatocytes, and round and early-elongating spermatids. Two protein bands of 177 and 17 0 kDa were detected in immunoblots of spermatocytes and round spermati ds, while bands of 148 and 142 kDa were prominent in preparations of e longating spermatids. Topo II levels and distribution patterns, as obs erved by immunofluorescent microscopy, exhibited cell type-specific va riations. Differences in topo II staining patterns were also apparent when nuclear matrices of spermatogenic cells were prepared with differ ent extraction conditions. In addition to its possible function as a s tructural component, topo II, associated with nuclear matrix preparati ons from spermatogenic cells, possessed catalytic activity. These obse rvations indicate that both the 177 and 170 kDa and the 148 and 142 kD a forms of topo II share similar structural and functional properties. Topo II beta mRNA was transcribed in rat spermatogenic cells at 6.2 k b. Relative levels of topo II beta mRNA were high in spermatogonia and spermatocytes, and decreased in both round and early-elongating sperm atids. Changes in topo II expression levels and localization patterns represent distinct stage-specific markers for the maturation of sperma togenic cells, and are consistent with the involvement of topo II in m ediating DNA modifications and chromatin changes during spermatogenesi s. (C) 1996 Wiley-Liss, Inc.