Spermatogenesis is an androgen-dependent process requiring intimate contact between the cells that directly respond to the androgenic signal (Sertoli cells) and the cells that ultimately become sperm (germ cells). While the androgen dependence of spermatogenesis has been known for several decades, its molecular basis has remained elusive. The subject of this proposal is an androgen/androgen receptor (AR)-induced transcription factor, RHOX5, which is expressed in Sertoli cells and therefore is a candidate to mediate androgen- dependent events during spermatogenesis. Loss of Rhox5 in mice loss causes increased male germ-cell apoptosis, reduced sperm count, and reduced sperm motility. Because Rhox5 is expressed in Sertoli cells, this suggests that Rhox5 regulates the transcription of genes encoding cell surface and secreted molecules in Sertoli cells that in turn regulate the survival and maturation of the adjacent germ cells. Microarray analysis has identified many genes regulated by Rhox5, including Unc5c, which encodes a pro-apoptotic cell-surface protein, and insulin-2, which encodes a secreted molecule that promotes metabolism and cell survival. Insulin-2 is a direct target of RHOX5 whose expression during the first wave of spermatogenesis depends on Rhox5. Other Rhox5-regulated genes include those encoding the key metabolic regulators PPAR?, PGC1?, resistin, and adiponectin, as well other members of the X-linked Rhox homeobox gene cluster. One of the Aims of this proposal is to begin to define the transcriptional network under the control of RHOX5, in part by using new technology to rapidly screen for more direct targets of RHOX5. These targets, including secondary androgen-response genes, will be characterized and their interrelationships with genes indirectly regulated by Rhox5 will be analyzed in order to begin to establish a Sertoli-cell transcriptional network. The Rhox5 gene is also a model system for elucidating molecular mechanisms that control gene transcription. The other Aim of this proposal focuses on a novel regulatory mechanism that controls the expression of Rhox5's proximal promoter (Pp), a promoter that recruits polymerase II (Pol II) and begins transcriptional elongation in all tissues but only completes transcriptional elongation to allow the production of RHOX5 protein in Sertoli and caput epididymal cells. Preliminary data indicates that completion of Pp transcriptional elongation depends, in part, on AR. This suggests a new function for this nuclear hormone receptor, as AR is classically thought to regulate gene expression only by recruiting Pol II and initiating transcription. In this application, we propose to elucidate the underlying molecular mechanism for this novel mode of regulating gene expression.

Public Health Relevance

The reproductive homeobox-5 (Rhox5) gene encodes a transcription factor. Because it is testosterone regulated and required for the normal fertility of male mice, studying Rhox5 has the potential to illuminate transcription networks responsible for hormone-regulated gene expression and fertility. In addition, Rhox5 is regulated by a novel transcriptional mechanism that may significantly add to our understanding of gene regulation in general.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD045595-20
Application #
8475356
Study Section
Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
Program Officer
Moss, Stuart B
Project Start
1991-05-01
Project End
2014-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
20
Fiscal Year
2013
Total Cost
$289,147
Indirect Cost
$101,997
Name
University of California San Diego
Department
Obstetrics & Gynecology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
De Gendt, Karel; Verhoeven, Guido; Amieux, Paul S et al. (2014) Genome-wide identification of AR-regulated genes translated in Sertoli cells in vivo using the RiboTag approach. Mol Endocrinol 28:575-91
Richardson, Marcy E; Bleiziffer, Andreas; Tuttelmann, Frank et al. (2014) Epigenetic regulation of the RHOX homeobox gene cluster and its association with human male infertility. Hum Mol Genet 23:12-23
Song, Hye-Won; Wilkinson, Miles F (2014) Transcriptional control of spermatogonial maintenance and differentiation. Semin Cell Dev Biol 30:14-26
Song, H W; Anderson, R A; Bayne, R A et al. (2013) The RHOX homeobox gene cluster is selectively expressed in human oocytes and male germ cells. Hum Reprod 28:1635-46
Maeder, Morgan L; Angstman, James F; Richardson, Marcy E et al. (2013) Targeted DNA demethylation and activation of endogenous genes using programmable TALE-TET1 fusion proteins. Nat Biotechnol 31:1137-42
MacLean 2nd, James A; Hayashi, Kanako; Turner, Terry T et al. (2012) The Rhox5 homeobox gene regulates the region-specific expression of its paralogs in the rodent epididymis. Biol Reprod 86:189
Bhardwaj, Anjana; Song, Hye-Won; Beildeck, Marcy et al. (2012) DNA demethylation-dependent AR recruitment and GATA factors drive Rhox5 homeobox gene transcription in the epididymis. Mol Endocrinol 26:538-49
Maclean, James A; Bettegowda, Anilkumar; Kim, Byung Ju et al. (2011) The rhox homeobox gene cluster is imprinted and selectively targeted for regulation by histone h1 and DNA methylation. Mol Cell Biol 31:1275-87
Hu, Zhiying; Dandekar, Dineshkumar; O'Shaughnessy, Peter J et al. (2010) Androgen-induced Rhox homeobox genes modulate the expression of AR-regulated genes. Mol Endocrinol 24:60-75
MacLean 2nd, James A; Wilkinson, Miles F (2010) The Rhox genes. Reproduction 140:195-213

Showing the most recent 10 out of 17 publications