Expression of inhibin-alpha is regulated synergistically by Wilms' tumor gene 1 (Wt1) and steroidogenic factor-1 (Sf1) in sertoli cells

WT1 suppresses follicle-stimulating hormone-induced progesterone secretion by regulating ERK1/2 pathway in chicken preovulatory granulosa cells

Multiple Wilms tumor gene 1 (WT1) splicing variants are expressed in mammals, and these variants regulate tumorigenesis and mediate the development of multiple tissues and organs, including gonads. However, WT1 splicing variants (+KTS or -KTS) are expressed in only two nonmammalian vertebrates, and unexpectedly, their functions in chicken ovaries remain elusive. Progesterone (P4) secreted by chicken granulosa cells (GCs) participates in various physiological processes and plays an important role in maintaining reproductive performance. The purpose of this study was to investigate the effect of WT1(+KTS) and WT1(-KTS) on chicken P4 secretion in preovulatory GCs. First, we detected WT1 mRNA expression in GCs from follicles of different developmental stages by Quantitative real-time PCR (RT-qPCR) and found that WT1 mRNA expression was considerably increased in preovulatory GCs compared with prehierarchical GCs. Primary cells collected from preovulatory follicles were treated with WT1(+KTS) or WT1(-KTS) overexpression vectors and subsequently cultured in the absence or presence of follicle-stimulating hormone (FSH). The mRNA levels of FSH-receptor (FSHR) and steroidogenesis genes were determined by RT-qPCR, and the P4 levels in the cell supernatants were measured by radioimmunoassay (RIA). Both WT1(+KTS) and WT1(-KTS) significantly decreased P4 secretion due to a reduction in FSHR, STAR and CYP11A1 mRNA levels. Western blotting revealed that ERK1/2 and BRAF phosphorylation levels were suppressed after overexpression of WT1(+KTS) or WT1(-KTS), whereas total protein and mRNA levels were not significantly changed. In addition, CREB protein and phosphorylation levels were inhibited after overexpression of WT1(+KTS) or WT1(-KTS). In conclusion, WT1(+KTS) and WT1(-KTS) inhibited CREB protein activity and significantly reduced FSHR, STAR and CYP11A1 mRNA levels, which subsequently suppressed FSH-induced P4 secretion in preovulatory GCs by modulating ERK1/2 signaling.

Association of polymorphism c.-124G>A and c.-16 C>T in the promoter region of human INHA gene with altered sperm parameters; A pilot study

OBJECTIVE

The objective of this was to demonstrate the association of Inhibin α (INHα) c.-124G>A and INHα-c.-16 C>T polymorphisms with altered sperm parameters in a selected male population of Karachi, Pakistan.

STUDY DESIGN & SETTINGS

In this pilot study, male subjects were stratified on the basis of the WHO criteria for altered sperm parameters; 83 (cases-altered sperm parameters) and 30 (controls-normal sperm parameters) subjects were included for analysis of INHα-c.124G>A polymorphism and 88 (cases) and 38 (controls) were analysed for INHα -c-16 C>T polymorphism. Genotyping of INHα-c.-124G>A and INHα-c.-16 C>T was performed by PCR-RFLP, genotype distribution in Hardy-Weinberg equilibrium was evaluated by binary logistic regression model.

RESULTS

For the c.-124G>A polymorphism in INHα gene, frequency of the three major genotypes in controls was: GG: 80.0%, GA: 20.0% and AA: 0% and in cases was: GG: 59.0%, GA: 30.2% and AA: 10.8%. The GG genotype was significantly associated with male infertility (P < .045, OR = 2.776, 95% CI = 1.025-7.513) while the GA genotype was not significantly associated with infertility (P < .290 OR = 0.580, 95% CI = 0.211-1.593). Frequency of mutant AA genotype was 10.8% in cases (altered sperm parameters) and absent (0%) in normal sperm parameter (controls). The frequencies of three major genotypes CC, CT and TT did not show any significant difference between cases and controls (P > .05).

CONCLUSION

The results from our study exhibited a significant association of c.-124G>A polymorphism in the INHα gene promoter region with male infertility in the Pakistani population. A significant association of c.-16 C>T polymorphism with male infertility, however, was not observed. Further large-scale studies should be conducted to confirm this association.

CRISPR/Cas9-induced disruption of wt1a and wt1b reveals their different roles in kidney and gonad development in Nile tilapia

Wilms tumor 1 (Wt1) is an essential factor for urogenital system development. Teleosts have two wt1s, named as wt1a and wt1b. In this study, the expression pattern of wt1a and wt1b and their functions on the urogenital system were analyzed by in situ hybridization and CRISPR/Cas9. wt1a was found to be expressed in the glomerulus at 3 dah (days after hatching), earlier than wt1b. wt1a and wt1b were simultaneously expressed in the somatic cells of gonads at 3 dah, while their cell locations were similar, but not identical in adult fish gonads. The wt1a^-/- fish displayed pericardial edema and yolk sac edema at 3 dah and subsequently expanded as general body edema at 6 dah, failed to develop glomerulus and died during 6-10 dah, whereas the wt1b^-/- fish were phenotypically normal. Immunohistochemical analyses revealed that the germ cell marker Vasa was expressed, while somatic cell genes Cyp19a1a, Amh, Gsdf and Dmrt1 were not expressed in the wt1a^-/- gonads at 6 dah. The sex phenotypes of XX and XY in the wt1b^-/- fish were not affected. Real-time PCR revealed that the ovarian cyp19a1a expression was up-regulated in XX wt1b^-/- fish, compared with XX control at 90 dah. Serum estradiol-17β level was also up-regulated in XX wt1b^-/- fish at 90 and 180 dah. The XY wt1b^-/- fish had normal serum estradiol-17β and 11-ketotestosterone levels and remained fertile. These results suggest that Wt1a and Wt1b have different functions in the kidneys and gonads of tilapia.

A new role for wilms tumor protein 1: differential activities of + KTS and -KTS variants to regulate LHβ transcription

Luteinizing hormone (LH) is synthesized and secreted throughout the reproductive cycle from gonadotrope cells in the anterior pituitary, and is required for steroidogenesis and ovulation. LH contains an α-subunit common with FSH, and a unique LHβ subunit that defines biological activity. Basal LHβ transcription is low and stimulated by hypothalamic GnRH, which induces synthesis of early growth response protein-1 (Egr1), and stimulates binding of transcription factors Egr1 and steroidogenic factor-1 (SF1) on the promoter. WT1 (Wilms tumor protein1) is a zinc finger transcription factor with an essential role in urogenital system development, and which regulates several reproductive genes via interactions with SF1 or binding to GC-rich elements such as Egr1 binding sites. We investigated a potential role for WT1 in LHβ transcription in clonal mouse gonadotrope LβT2 cells. WT1 was present in LβT2 and mouse pituitary cells, and protein bound to the endogenous LHβ promoter. Interestingly, mRNAs for WT1(+KTS), which contains a three amino-acid insertion between the 3rd and 4th zinc fingers, and the WT1 (-KTS) variant were both expressed at significant levels. WT1 mRNAs and protein were decreased approximately 50% by GnRH treatment, under conditions where Egr1 mRNA and protein, and LHβ transcription, were stimulated. Decreasing expression of mRNA for WT1 (-KTS) decreased stimulation of LHβ and Egr1 by GnRH, whereas decreasing both WT1 (-KTS) and (+KTS) increased endogenous LHβ transcription, and prevented LHβ but not Egr1 stimulation by GnRH, suggesting differing biological activities for the WT1 isoforms. Overexpression of WT1 showed that WT1(-KTS) enhanced LHβ promoter GnRH stimulation 2-to-3-fold and required the 3'Egr1 site, but WT1(+KTS) repressed both basal and GnRH-stimulated LHβ promoter activity by approximately 70%. Our data suggest that WT1 can modulate LHβ transcription, with differential roles for the two WT1 variants; WT1 (-KTS) enhances and WT1 (+KTS) suppresses transcription.

Inhibin alpha gene expression in human trophoblasts is regulated by interactions between TFAP2 and cAMP signaling pathways

Inhibin α (Inha) gene expression is regulated, in rat granulosa cells, via a cyclic 3',5'-adenosine monophosphate (AMP)-response element (CRE) found in a region of the promoter that is homologous to the human INHA promoter. We previously found that during in vitro cytotrophoblast differentiation, human INHA gene expression was regulated by TFAP2A via association with an AP-2 site located upstream of this CRE. The aim of this study was to evaluate if the human INHA gene was also regulated by cAMP in trophoblasts, and to investigate the possible crosstalk between TFAP2 and cAMP signaling pathways in the regulation of INHA gene expression. Treatment with cAMP or forskolin increased INHA mRNA expression by 7- and 2-fold in primary cytotrophoblasts and choriocarcinoma-derived BeWo cells, respectively. Treatment with the protein kinase A inhibitor H-89 reduced forskolin-induced luciferase activity by ∼40% in BeWo cells transfected with an INHA promoter-driven luciferase reporter vector. TFAP2 overexpression increased basal luciferase activity, whereas the dominant repressor KCREB abolished it. Surprisingly, mutation of the CRE also eliminated the TFAP2-induced transcription, although TFAP2 overexpression was still able to increase forskolin-induced luciferase activity when the AP-2 binding site, but not the CRE site, was mutated. Thus, INHA gene expression is upregulated by cAMP via CRE in human trophoblasts, and TFAP2 regulates this expression by interacting with CRE.

Mechanisms of transcriptional regulation by WT1 (Wilms' tumour 1)

The WT1 (Wilms' tumour 1) gene encodes a zinc finger transcription factor and RNA-binding protein that direct the development of several organs and tissues. WT1 manifests both tumour suppressor and oncogenic activities, but the reasons behind these opposing functions are still not clear. As a transcriptional regulator, WT1 can either activate or repress numerous target genes resulting in disparate biological effects such as growth, differentiation and apoptosis. The complex nature of WT1 is exemplified by a plethora of isoforms, post-translational modifications and multiple binding partners. How WT1 achieves specificity to regulate a large number of target genes involved in diverse physiological processes is the focus of the present review. We discuss the wealth of the growing molecular information that defines our current understanding of the versatility and utility of WT1 as a master regulator of organ development, a tumour suppressor and an oncogene.