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

Abstract

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 II 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 II mRNA levels in prepubertal testis, continued treatment failed to enhance topo II mRNA above postpubertal control levels. The extent of topo II activity remained steady regardless of the testosterone-induced increase in topo II mRNA levels. Inhibition of testosterone function in postpubertal animals by ethanedimethane sulphonate (EDS) and flutamide resulted in a significant decrease in topo II gene expression and topo II activity. The administration of exogenous testosterone (T) to EDS-and flutamide-treated rats restored topo II 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 II expression. Our results reveal that testosterone acts as a positive regulator of topo II gene expression and is required for the maintenance of topo II expression during the development of the postnatal testis and spermatogenesis.

Relationships between sperm DNA fragmentation, sperm apoptotic markers and serum levels of CB-153 and p,p′-DDE in European and Inuit populations

“…In rodents, it has recently been demonstrated that testosterone increased expression of DNA topoisomerase II, the key enzyme that nicks and ligates DNA molecules during the histone-to-protamine transition process (Marcon & Boissonneault 2004). Moreover, testosterone is required for the maintenance of topoisomerase II expression during spermatogenesis (McPherson & Longo 1993, Bakshi et al 2001. A Swedish study on young males reported a weak, negative association, between CB-153 and free testosterone levels (Richthoff et al 2003).…”

Chromatin Remodeling in Spermatids: A Sensitive Step for the Genetic Integrity of the Male Gamete

“…It has been proposed that topoisomerase II may be responsible for the strand breakage and ligation steps in both the rat and chicken models [8,30,38]. In contrast, Bakshi et al have shown that topoisomerase II was not expressed in rat spermatids [1]. Hence, the topology-modifying enzymes involved in the process remains to be identified.…”

Gene expression changes are age‐dependent and lobe‐specific in the brown Norway rat model of prostatic hyperplasia

“…Topo2a and Stmn1 serve as substrates for Aurkb during mitosis [21, 22] and promote chromosome segregation during cell proliferation [23, 24]; activities that may have relevance to prostatic epithelial cell hyperplasia in the lateral lobe of aging rats. In the lateral lobe of 4 month old rats, Topo2a immunostaining was localized to nuclei of widely dispersed luminal epithelial cells as well as some basal epithelial cells and stromal cells (Fig.…”

“…Although we do not know the phosphorylation status of Stmn1 in the lateral lobe, upregulation and differential phosphorylation of human Stmn1 have been observed in prostate cancer specimens and cell lines [44]. Interestingly, Topo2a, Aurkb, and Stmn1 are co-expressed in proliferating germ cells of the testis [24, 33, 41, 45]. Given their key roles in proper cell division, Stmn1, Aurkb, and Topo2a serve as robust markers of cell proliferation in the Brown Norway rat lateral prostate and if overexpressed could lead to the accumulation of chromosomal abnormalities.…”