Developmental and hormonal regulation of type II DNA topoisomerase in rat testis

Type II DNA topoisomerase (topo II) is required for diverse biological functions including DNA replication, maintenance of genome stability, chromosome segregation and chromosome condensation. While the identity of topo II in rodent testis has been established, the regulation of topo II expression during the development of the postnatal testis and gametogenesis is unclear. Here, we report that rat testis topo II is developmentally and hormonally regulated. Topo IIα mRNA levels peaked prior to the onset of puberty, declined sharply thereafter and stabilized in adult testis. In contrast, the topo II enzyme content was lower in prepubertal testis but increased after the onset of puberty. Topo II was expressed in a cell-specific manner within germ cells, being detected only in pachytene spermatocytes. While testosterone markedly increased topo IIα mRNA levels in prepubertal testis, continued treatment failed to enhance topo IIα mRNA above postpubertal control levels. The extent of topo II activity remained steady regardless of the testosterone-induced increase in topo IIα mRNA levels. Inhibition of testosterone function in postpubertal animals by ethanedimethane sulphonate (EDS) and flutamide resulted in a significant decrease in topo IIα gene expression and topo II activity. The administration of exogenous testosterone (T) to EDS- and flutamide-treated rats restored topo IIα mRNA levels and topo II activity similar to the levels seen in the testis of age-matched control animals. Histochemical analyses of testes indicated that the effect of T on spermatogenesis was separable from its effect on topo IIα expression. Our results reveal that testosterone acts as a positive regulator of topo IIα gene expression and is required for the maintenance of topo IIα expression during the development of the postnatal testis and spermatogenesis.