Targeted Inactivation of Testicular Nuclear Orphan Receptor 4 Delays and Disrupts Late Meiotic Prophase and Subsequent Meiotic Divisions of Spermatogenesis

Abstract

Testicular orphan nuclear receptor 4 (TR4) is specifically and stage-dependently expressed in late-stage pachytene spermatocytes and round spermatids. In the developing mouse testis, the highest expression of TR4 can be detected at postnatal days 16 to 21 when the first wave of spermatogenesis progresses to late meiotic prophase. Using a knockout strategy to delete TR4 in mice, we found that sperm production in TR4 ؊/؊ mice is reduced. The comparison of testes from developing TR4 ؉/؉ and TR4 ؊/؊ mice shows that spermatogenesis in TR4؊/؊ mice is delayed. Analysis of the first wave of spermatogenesis shows that the delay can be due to delay and disruption of spermatogenesis at the end of late meiotic prophase and subsequent meiotic divisions. Seminiferous tubule staging shows that stages X to XII, where late meiotic prophase and meiotic divisions take place, are delayed and disrupted in TR4 ؊/؊ mice. Histological examination of testis sections from TR4 ؊/؊ mice shows degenerated primary spermatocytes and some necrotic tubules. Testis-specific gene analyses show that the expression of sperm 1 and cyclin A1, which are genes expressed at the end of meiotic prophase, was delayed and decreased in TR4 ؊/؊ mouse testes. Taken together, results from TR4 ؉/؉ and TR4 ؊/؊ mice indicate that TR4 is essential for normal spermatogenesis in mice.The orphan receptors belong to the nuclear receptor superfamily, members of which mediate extracellular signals to transcriptional response. The roles of orphan receptors have been linked to animal development, cellular differentiation, and homeostasis. The human testicular orphan receptor 4 (TR4) was originally isolated from testis and prostate cDNA libraries by PCR (3). While TR4 shares the structural features of nuclear receptors, no ligand has been identified, and it is therefore considered an orphan receptor. TR4 is relatively highly expressed in several tissues including testis, kidney, and muscle (6). Northern blot analyses from multiple human and mouse tissues show a 9.4-and a 2.8-kb transcript. The 9.4-kb transcript is expressed ubiquitously, while the 2.8-kb transcript is largely restricted to the testis (6, 7). In testes, TR4 is specifically expressed in germ cells (6, 7).TR4 can modulate its target gene expression by forming homodimers and binding to AGGTCA direct repeat sequences in its target genes (9). We have demonstrated that TR4 can modulate many signal transduction pathways, such as those involving retinoic acid (11), the thyroid hormone (12), vitamin D (12), and ciliary neurotrophic factor (25). TR4 also can modulate transactivation mediated by other steroid nuclear receptors through interaction with these steroid receptors. Our group demonstrated that TR4 could interact with the androgen receptor (AR) and the estrogen receptor and thus suppress AR-and estrogen receptor-mediated transactivation (10,19). Recently TR2 and TR4 heterodimers have been found in the core of a larger erythroid epsilon-globulin gene repressor complex called DRED, which represses embryonic and ...

Growth retardation and abnormal maternal behavior in mice lacking testicular orphan nuclear receptor 4

“…4A) TR4 Ϫ/Ϫ mice. TR4 Ϫ/Ϫ males show a disruption of spermatogenesis during late meiotic prophase and through subsequent meiotic divisions, and testis sections from TR4 Ϫ/Ϫ mice show degeneration of primary spermatocytes and necrotic tubules (38).…”

CIB1 Is Essential for Mouse Spermatogenesis

“…During mouse postnatal testis development, meiosis II in males first occurs around 18 days of age, and the first set of elongated spermatids do not appear until 25 to 30 days (25,41,49). Analysis of gene and protein expression of testis samples at different developmental stages helped us to determine where and how defects occur during Cib1 Ϫ/Ϫ testis development.…”

“…The possible regulatory roles of CIB1 in spermatogenesis were tested first by determining which gene expression patterns were altered in the Cib1 Ϫ/Ϫ testis via RT-PCR. We initially examined the expression of stage-specific marker genes that appear during meiosis, i.e., Hsp70-2 (heat shock protein, chaperone) and Sprm-1 (POU homeodomain domain [5,15,25,36]) but found comparable mRNA expression levels in Cib1 ϩ/ϩ and Cib1 Ϫ/Ϫ testis samples (Fig. 4A).…”

Deficiency in TR4 nuclear receptor abrogates Gadd45a expression and increases cytotoxicity induced by ionizing radiation

“…Mice lacking Tr4 ( TR4KO ) have high rates of early postnatal mortality, show significant growth retardation [12], display reproductive defects in both genders [12, 13], abnormalities in spermatogenesis [14], reduced lipoprotein metabolism [15, 16], and reduced gluconeogenesis [17], as well as defects in cerebella development [18]. Furthermore, the premature aging phenotype of TR4KO mouse led to the finding of TR4’s role in defending oxidative stress and DNA damage response [19].…”