Germ Cell Nuclear Factor (GCNF/RTR) Regulates Transcription of Gonadotropin-Regulated Testicular RNA Helicase (GRTH/DDX25) in Testicular Germ Cells--The Androgen Connection.

Abstract

Gonadotropin-regulated testicular RNA helicase (GRTH) (GRTH/DDX25), is a testis-specific protein essential for completion of spermatogenesis. Transgenic mice carrying 5'-flanking regions of the GRTH gene/green fluorescence protein (GFP) reporter revealed a region (-6.4/-3.6 kb) which directs its expression in germ cells (GCs) via androgen action. This study identifies a functional cis-binding element on the GRTH gene for GC nuclear factor (GCNF) (GCNF/RTR) required to regulate GRTH gene expression in postmeiotic testis GCs and explore the action of androgen on GCNF and GRTH transcription/expression. GCNF expression decreased in mice testis upon flutamide (androgen receptor antagonist) treatment, indicating the presence of an androgen/GCNF network to direct GRTH expression in GC. Binding studies and chromatin immunoprecipitation demonstrated specific association of GCNF to a consensus half-site (-5270/-5252) of the GRTH gene in both round spermatids and spermatocytes, which was abolished by flutamide treatment in round spermatids. Moreover, flutamide treatment of wild-type mice caused selective reduction of GCNF and GRTH in round spermatids. GCNF knock-down in seminiferous tubules from GRTH-transgenic mice (dark zone, round spermatid rich) caused decreased GFP expression. Exposure of tubules to flutamide caused decrease in GCNF and GFP expression, whereas androgen exposure induced significant increase. Our studies provide evidence for actions of androgen on GCNF cell-specific regulation of GRTH expression in GC. GRTH associates with GCNF mRNA, its absence caused increase on GCNF expression and mRNA stability indicative of a negative autocrine regulation of GCNF by GRTH. These in vivo/in vitro models link androgen actions to GC through GCNF, as regulated transfactor that controls transcription/expression of GRTH.