The orphan nuclear receptors COUP-TFI and COUP-TFII regulate expression of the gonadotropin LHβ gene

Evidence for NR2F2/COUP-TFII involvement in human testis development

NR2F2 encodes COUP-TFII, an orphan nuclear receptor required for the development of the steroidogenic lineages of the murine fetal testes and ovaries. Pathogenic variants in human NR2F2 are associated with testis formation in 46,XX individuals, however, the function of COUP-TFII in the human testis is unknown. We report a de novo heterozygous variant in NR2F2 (c.737G > A, p.Arg246His) in a 46,XY under-masculinized boy with primary hypogonadism. The variant, located within the ligand-binding domain, is predicted to be highly damaging. In vitro studies indicated that the mutation does not impact the stability or subcellular localization of the protein. NR5A1, a related nuclear receptor that is a key factor in gonad formation and function, is known to physically interact with COUP-TFII to regulate gene expression. The mutant protein did not affect the physical interaction with NR5A1. However, in-vitro assays demonstrated that the mutant protein significantly loses the inhibitory effect on NR5A1-mediated activation of both the LHB and INSL3 promoters. The data support a role for COUP-TFII in human testis formation. Although mutually antagonistic sets of genes are known to regulate testis and ovarian pathways, we extend the list of genes, that together with NR5A1 and WT1, are associated with both 46,XX and 46,XY DSD.

The Nuclear Receptor Seven Up Regulates Genes Involved in Immunity and Xenobiotic Response in the Adult Drosophila Female Fat Body

The physiology of organisms depends on inter-organ communication in response to changes in the environment. Nuclear receptors are broadly expressed transcription factors that respond to circulating molecules to control many biological processes, including immunity, detoxification, and reproduction. Although the tissue-intrinsic roles of nuclear receptors in reproduction have been extensively studied, there is increasing evidence that nuclear receptor signaling in peripheral tissues can also influence oogenesis. We previously showed that the Drosophila nuclear receptor Seven up (Svp) is required in the adult fat body to regulate distinct steps of oogenesis; however, the relevant downstream targets of Svp remain unknown. Here, we took an RNA sequencing approach to identify candidate Svp targets specifically in the adult female fat body that might mediate this response. svp knockdown in the adult female fat body significantly downregulated immune genes involved in the first line of pathogen defense, suggesting a role for Svp in stimulating early immunity. In addition, we found that Svp transcriptionally regulates genes involved in each step of the xenobiotic detoxification response. Based on these findings, we propose a testable model in which Svp functions in the adult female fat body to stimulate early defense against pathogens and facilitate detoxification as part of its mechanisms to promote oogenesis.

Egg-laying and brooding stage-specific hormonal response and transcriptional regulation in pituitary of Muscovy duck (Cairina moschata)

Broodiness is an interesting topic in reproductive biology for its reduced egg production. The strong brooding trait of Muscovy duck has become a major factor restricting the development of its industry. Broody phenotype and environmental factors influencing broodiness in poultry have been extensively studied, but the molecular regulation mechanism of broodiness remains unclear. In this research, the Muscovy duck reproductive endocrine hormones and pituitary transcriptome profiles during egg-laying phases (LP) and brooding phases (BP) were studied. During BP (n = 19), prolactin (PRL) levels was higher, while progesterone (P4) and estradiol (E2) were lower as compared to ducks during their LP (n = 20) (P < 0.01). We then examined the pituitary transcriptome of Muscovy duck at the 2 reproductive stages. A total of 398 differentially expressed genes included 20 transcription factors were identified (fold change ≥ 1.5, P < 0.01). There were 109 upregulated and 289 downregulated genes at brooding phases (n = 6) compared with egg-laying phases (n = 6). Real-time quantitative PCR analysis was carried out to verify the transcriptome results. The present study suggested that neuroactive ligand-receptor interaction pathway, calcium signaling pathway, and response to steroid hormones biological process are critical for controlling broodiness in the ducks. Further analysis revealed that SHH, PTGS2, RLN3, and transcription factor AP-1 may act as central signal modulators of hormonal and behavioral regulation mechanism associated with broodiness.

The nuclear receptor seven up functions in adipocytes and oenocytes to control distinct steps of Drosophila oogenesis

Reproduction is intimately linked to the physiology of an organism. Nuclear receptors are widely expressed transcription factors that mediate the effects of many circulating molecules on physiology and reproduction. While multiple studies have focused on the roles of nuclear receptors intrinsically in the ovary, it remains largely unknown how the actions of nuclear receptors in peripheral tissues influence oogenesis. We identified the nuclear receptor encoded by svp as a novel regulator of oogenesis in adult Drosophila. Global somatic knockdown of svp reduces egg production by increasing GSC loss, death of early germline cysts, and degeneration of vitellogenic follicles. Tissue-specific knockdown experiments revealed that svp remotely controls these different steps of oogenesis through separate mechanisms involving distinct tissues. Specifically, adipocyte-specific svp knockdown impairs GSC maintenance and early germline cyst survival, whereas oenocyte-specific svp knockdown increases the death of vitellogenic follicles without any effects on GSCs or early cysts. These results illustrate that nuclear receptors can control reproduction through a variety of mechanisms involving peripheral tissues.

The Nuclear Receptor COUP-TFII Regulates Amhr2 Gene Transcription via a GC-Rich Promoter Element in Mouse Leydig Cells

The nuclear receptor chicken ovalbumin upstream promoter–transcription factor type II (COUP-TFII)/NR2F2 is expressed in adult Leydig cells, and conditional deletion of the Coup-tfii/Nr2f2 gene impedes their differentiation. Steroid production is also reduced in COUP-TFII–depleted Leydig cells, supporting an additional role in steroidogenesis for this transcription factor. COUP-TFII action in Leydig cells remains to be fully characterized. In the present work, we report that COUP-TFII is an essential regulator of the gene encoding the anti-Müllerian hormone receptor type 2 (Amhr2), which participates in Leydig cell differentiation and steroidogenesis. We found that Amhr2 mRNA levels are reduced in COUP-TFII–depleted MA-10 Leydig cells. Consistent with this, COUP-TFII directly activates a −1486 bp fragment of the mouse Amhr2 promoter in transient transfection assays. The COUP-TFII responsive region was localized between −67 and −34 bp. Chromatin immunoprecipitation assay confirmed COUP-TFII recruitment to the proximal Amhr2 promoter whereas DNA precipitation assay revealed that COUP-TFII associates with the −67/−34 bp region in vitro. Even though the −67/−34 bp region contains an imperfect nuclear receptor element, COUP-TFII–mediated activation of the Amhr2 promoter requires a GC-rich sequence at −39 bp known to bind the specificity protein (SP)1 transcription factor. COUP-TFII transcriptionally cooperates with SP1 on the Amhr2 promoter. Mutations that altered the GCGGGGCGG sequence at −39 bp abolished COUP-TFII–mediated activation, COUP-TFII/SP1 cooperation, and reduced COUP-TFII binding to the proximal Amhr2 promoter. Our data provide a better understanding of the mechanism of COUP-TFII action in Leydig cells through the identification and regulation of the Amhr2 promoter as a novel target.

Two Hormones for One Receptor: Evolution, Biochemistry, Actions, and Pathophysiology of LH and hCG

LH and chorionic gonadotropin (CG) are glycoproteins fundamental to sexual development and reproduction. Because they act on the same receptor (LHCGR), the general consensus has been that LH and human CG (hCG) are equivalent. However, separate evolution of LHβ and hCGβ subunits occurred in primates, resulting in two molecules sharing ~85% identity and regulating different physiological events. Pituitary, pulsatile LH production results in an ~90-minute half-life molecule targeting the gonads to regulate gametogenesis and androgen synthesis. Trophoblast hCG, the "pregnancy hormone," exists in several isoforms and glycosylation variants with long half-lives (hours) and angiogenic potential and acts on luteinized ovarian cells as progestational. The different molecular features of LH and hCG lead to hormone-specific LHCGR binding and intracellular signaling cascades. In ovarian cells, LH action is preferentially exerted through kinases, phosphorylated extracellular-regulated kinase 1/2 (pERK1/2) and phosphorylated AKT (also known as protein kinase B), resulting in irreplaceable proliferative/antiapoptotic signals and partial agonism on progesterone production in vitro. In contrast, hCG displays notable cAMP/protein kinase A (PKA)-mediated steroidogenic and proapoptotic potential, which is masked by estrogen action in vivo. In vitro data have been confirmed by a large data set from assisted reproduction, because the steroidogenic potential of hCG positively affects the number of retrieved oocytes, and LH affects the pregnancy rate (per oocyte number). Leydig cell in vitro exposure to hCG results in qualitatively similar cAMP/PKA and pERK1/2 activation compared with LH and testosterone. The supposed equivalence of LH and hCG has been disproved by such data, highlighting their sex-specific functions and thus deeming it an oversight caused by incomplete understanding of clinical data.

Expression, regulation, and promoter activation of vanin-2 (VNN2) in bovine follicles prior to ovulation

Vanin-2 (VNN2) is known to be involved in inflammation and leukocyte migration, but its regulation in follicles remains unknown. The objectives of this work were to study the regulation of VNN2 transcripts in bovine follicles prior to ovulation and to characterize the control of its expression in bovine granulosa cells. VNN2 expression was studied using total RNA extracted from granulosa cells of small follicles (2-4 mm in diameter), dominant follicles obtained on Day 5 of the estrous cycle, ovulatory follicles obtained 0-24 h after human chorionic gonadotropin (hCG), and corpora lutea on Day 5 of the cycle. The results from RT-PCR analyses showed that levels of VNN2 mRNA were high in ovulatory follicles 24 h post-hCG but low in the other tissues. In ovulatory follicles, levels of VNN2 mRNA were low at 0 h but significantly up-regulated 12-24 h post-hCG. To determine factors controlling VNN2 gene expression, established primary cultures of granulosa cells isolated from bovine dominant follicles were used. Treatment with forskolin elevated VNN2 mRNA expression as observed in vivo. Mutation studies identified the minimal region conferring basal and forskolin-stimulated VNN2 promoter activities, which were dependent on chicken ovalbumin upstream promoter-transcription factor (COUP-TF), GATA, and Ebox cis-elements. Electrophoretic mobility shift assays identified COUP-TF, GATA4, and upstream stimulating factor proteins as key factors interacting with these elements. Chromatin immunoprecipitation assays confirmed basal and forskolin-induced interactions between these proteins and the VNN2 promoter in bovine granulosa cell cultures. VNN2 promoter activity and mRNA expression were markedly stimulated by forskolin and overexpression of the catalytic subunit of PKA, but inhibited by PKA and ERK1/2 inhibitors. Collectively, the findings from this study describe for the first time the gonadotropin/forskolin-dependent up-regulation of VNN2 transcripts in granulosa cells of preovulatory follicles and provide insights into some of the molecular bases of VNN2 gene expression in follicular cells.

Proposed role for COUP-TFII in regulating fetal Leydig cell steroidogenesis, perturbation of which leads to masculinization disorders in rodents

Reproductive disorders that are common/increasing in prevalence in human males may arise because of deficient androgen production/action during a fetal ‘masculinization programming window’. We identify a potentially important role for Chicken Ovalbumin Upstream Promoter-Transcription Factor II (COUP-TFII) in Leydig cell (LC) steroidogenesis that may partly explain this. In rats, fetal LC size and intratesticular testosterone (ITT) increased ∼3-fold between e15.5-e21.5 which associated with a progressive decrease in the percentage of LC expressing COUP-TFII. Exposure of fetuses to dibutyl phthalate (DBP), which induces masculinization disorders, dose-dependently prevented the age-related decrease in LC COUP-TFII expression and the normal increases in LC size and ITT. We show that nuclear COUP-TFII expression in fetal rat LC relates inversely to LC expression of steroidogenic factor-1 (SF-1)-dependent genes (StAR, Cyp11a1, Cyp17a1) with overlapping binding sites for SF-1 and COUP-TFII in their promoter regions, but does not affect an SF-1 dependent LC gene (3β-HSD) without overlapping sites. We also show that once COUP-TFII expression in LC has switched off, it is re-induced by DBP exposure, coincident with suppression of ITT. Furthermore, other treatments that reduce fetal ITT in rats (dexamethasone, diethylstilbestrol (DES)) also maintain/induce LC nuclear expression of COUP-TFII. In contrast to rats, in mice DBP neither causes persistence of fetal LC COUP-TFII nor reduces ITT, whereas DES-exposure of mice maintains COUP-TFII expression in fetal LC and decreases ITT, as in rats. These findings suggest that lifting of repression by COUP-TFII may be an important mechanism that promotes increased testosterone production by fetal LC to drive masculinization. As we also show an age-related decline in expression of COUP-TFII in human fetal LC, this mechanism may also be functional in humans, and its susceptibility to disruption by environmental chemicals, stress and pregnancy hormones could explain the origin of some human male reproductive disorders.

GATA transcription factors regulate LHβ gene expression

The GATA family of transcription factors are critical determinants of cell differentiation as well as regulation of adult gene expression throughout the reproductive axis. Within the anterior pituitary gland, GATA factors have been shown to increase glycoprotein α-subunit gene promoter activity; however, nothing has been known about the impact of these factors on expression of the gonadotropin β-subunits. In this study, we demonstrate expression of both GATA2 and GATA4 in primary mouse gonadotropes and the gonadotrope cell line, LβT2. Based on the transient transfection in fibroblast cells, GATA factors increase LH β-subunit gene (LHβ) promoter activity alone and in synergy with the orphan nuclear receptors steroidogenic factor-1 (SF-1) and liver receptor homologue-1 (LRH-1). The GATA response was localized to a DNA regulatory region at position -101 in the rat LHβ gene promoter which overlaps with a previously described cis-element for pituitary homeobox-1 (Pitx1) and is flanked by two SF-1/LRH-1 regulatory sites. As determined by gel shift, GATA and Pitx1 can compete for binding to this element. Furthermore, mutation analysis revealed a requirement for both the GATA/Pitx1 and the SF-1/LRH-1 cis-elements in order to achieve synergy. These studies identify a novel role for GATA transcription factors in the pituitary and reveal additional molecular mechanisms by which precise modulation of LHβ gene expression can be achieved.