Expression of germ cell nuclear factor (GCNF/RTR) during spermatogenesis

Abstract

Germ cell nuclear factor (GCNF/RTR), a novel orphan receptor in the nuclear receptor superfamily of ligand-activated transcription factors, is expressed predominantly in developing germ cells. In several mammalian species two GCNF/RTR mRNAs are present in the testis, with the smaller 2.3-kb transcript generally expressed at higher levels than the larger 7.4- or 8.0-kb transcript. In both the mouse and rat, the 2.3- and 7.4-kb GCNF/RTR transcripts were detected in isolated spermatogenic cells, but not in Sertoli cells. Expression of these transcripts is differentially regulated, with the larger 7.4-kb mRNA appearing earlier during testicular development. The major 2.3-kb transcript is expressed predominantly in round spermatids in the mouse and rat. In situ hybridization studies in the rat demonstrated that GCNF/RTR transcripts reach maximal steady-state levels in round spermatids at stages VII and VIII of the spermatogenic cycle, and then decline abruptly as spermatids begin to elongate. RNase protection assays were used to predict the 3' termination site of the 2.3-kb transcript. An alternative polyadenylation signal (AGUAAA) was identified just upstream of this termination site. These studies suggest that GCNF/RTR may regulate transcription during spermatogenesis, particularly in round spermatids just prior to the initiation of nuclear elongation and condensation.

Transcriptional and translational regulation of gene expression in haploid spermatids

“…PAF-1 is thought to be a novel orphan receptor in the nuclear receptor superfamily of ligand-activated transcription factors. In addition, TAK1 (Hirose et al 1994(Hirose et al , 1995b, Tr2-11 (CH Lee et al 1996), and Germ cell nuclear factor/retinoid receptor-related testis-associated receptor (GCNF/RTR) (Chen et al 1994;Hirose et al 1995a;Zhang et al 1998) are orphan receptors that have been demonstrated in testis of mouse (Chen et al 1994;Hirose et al 1995a) and man (Süsens and Borgmeyer 1996;Lei et al 1997). Like PAF-1, GCNF/RTR is expressed in round spermatids, but declines abruptly as spermatids start to elongate.…”

Analysis of Germ Cell Nuclear Factor Transcripts and Protein Expression During Spermatogenesis1

“…Gcnf transcription is confined to germ cells in both the testis and ovary [1,2]. In males Gcnf transcription occurs at lower levels during the meiotic prophase in rats and mice [4] and increases substantially in postmeiotic germ cells, with maximum levels in stage VI-VIII round spermatids [4,5]. In female mice Gcnf mRNA is present in growing oocytes, but it is undetectable in oocytes within primordial follicles [5].…”

“…Only the larger 7.4 kb Gcnf transcript has been identified in mouse embryos [7], embryonal carcinoma cell lines [20], and in some somatic tissues at significantly lower levels [1,21]. In contrast, spermatogenic cells express both 7.4 and 2.1 kb Gcnf transcripts [2,4,5]. The 7.4 kb transcript is expressed earlier during testicular development and is the predominant Gcnf mRNA in pachytene spermatocytes [4].…”

“…In contrast, spermatogenic cells express both 7.4 and 2.1 kb Gcnf transcripts [2,4,5]. The 7.4 kb transcript is expressed earlier during testicular development and is the predominant Gcnf mRNA in pachytene spermatocytes [4]. The smaller Gcnf transcript is expressed predominantly in haploid round spermatids [4,5].…”

“…Although two Gcnf transcripts have been identified in mouse [1,2,4,5], rat [4,5], and human testes [3,21], little is known about the structural or functional differences between these transcripts. The aims of this study were to characterize the structure and sequence of Gcnf and its distinct transcripts and to determine the expression and distribution of the GCNF protein during mouse spermatogenesis.…”