Modulation of endogenous GATA-4 activity reveals its dual contribution to Müllerian inhibiting substance gene transcription in Sertoli cells

Association of a GATA Binding Protein 4 Polymorphism with the Risk of Hypospadias in the Chinese Children

PURPOSE

GATA binding protein 4 (GATA4) has been implicated in the etiology of congenital malformation of the urogenital system. The present study investigated the influence of GATA4 polymorphisms on susceptibility to hypospadias.

METHODS

We genotyped 4 potentially functional polymorphisms (rs12458, rs12825, rs884662, and rs904018) in GATA4 in the hospital-based case-control study including 410 child patients and 520 nonmalformed individuals by the TaqMan MGB method. Risk associations were assessed using unconditional logistic regression, adjusted for potential confounding factors.

RESULTS

A significant association was found between rs12458 (3'-UTR of GATA4) and susceptibility to hypospadias (p = 0.008). Compared with rs12458 AA genotype individuals, those harboring the variant allele (rs12458 AT/TT) were correlated with significantly higher risk of hypospadias (AT/TT vs. AA: OR = 1.42, 95% CI = 1.17-2.35, p = 0.036). Furthermore, the rs12458T allele showed significantly decreased activity in a luciferase reporter assay, indicating a possible role of rs12458 variant in regulating the combination of microRNAs with the GATA4 mRNA.

CONCLUSIONS

The present results indicate that the functional GATA4 rs12458 variant confers individuals' susceptibility to hypospadias, possibly through regulating the GATA4 expression level.

Deletion of the Prdm3 Gene Causes a Neuronal Differentiation Deficiency in P19 Cells

PRDM (PRDI-BF1 (positive regulatory domain I-binding factor 1) and RIZ1 (retinoblastoma protein-interacting zinc finger gene 1) homologous domain-containing) transcription factors are a group of proteins that have a significant impact on organ development. In our study, we assessed the role of Prdm3 in neurogenesis and the mechanisms regulating its expression. We found that Prdm3 mRNA expression was induced during neurogenesis and that Prdm3 gene knockout caused premature neuronal differentiation of the P19 cells and enhanced the growth of non-neuronal cells. Interestingly, we found that Gata6 expression was also significantly upregulated during neurogenesis. We further studied the regulatory mechanism of Prdm3 expression. To determine the role of GATA6 in the regulation of Prdm3 mRNA expression, we used a luciferase-based reporter assay and found that Gata6 overexpression significantly increased the activity of the Prdm3 promoter. Finally, the combination of retinoic acid receptors α and β, along with Gata6 overexpression, further increased the activity of the luciferase reporter. Taken together, our results suggest that in the P19 cells, PRDM3 contributed to neurogenesis and its expression was stimulated by the synergism between GATA6 and the retinoic acid signaling pathway.

A Hormone That Lost Its Receptor: Anti-Müllerian Hormone (AMH) in Zebrafish Gonad Development and Sex Determination

Fetal mammalian testes secrete Anti-Müllerian hormone (Amh), which inhibits female reproductive tract (Müllerian duct) development. Amh also derives from mature mammalian ovarian follicles, which marks oocyte reserve and characterizes polycystic ovarian syndrome. Zebrafish (Danio rerio) lacks Müllerian ducts and the Amh receptor gene amhr2 but, curiously, retains amh To discover the roles of Amh in the absence of Müllerian ducts and the ancestral receptor gene, we made amh null alleles in zebrafish. Results showed that normal amh prevents female-biased sex ratios. Adult male amh mutants had enormous testes, half of which contained immature oocytes, demonstrating that Amh regulates male germ cell accumulation and inhibits oocyte development or survival. Mutant males formed sperm ducts and some produced a few offspring. Young female mutants laid a few fertile eggs, so they also had functional sex ducts. Older amh mutants accumulated nonvitellogenic follicles in exceedingly large but sterile ovaries, showing that Amh helps control ovarian follicle maturation and proliferation. RNA-sequencing data partitioned juveniles at 21 days postfertilization (dpf) into two groups that each contained mutant and wild-type fish. Group21-1 upregulated ovary genes compared to Group21-2, which were likely developing as males. By 35 dpf, transcriptomes distinguished males from females and, within each sex, mutants from wild types. In adult mutants, ovaries greatly underexpressed granulosa and theca genes, and testes underexpressed Leydig cell genes. These results show that ancestral Amh functions included development of the gonadal soma in ovaries and testes and regulation of gamete proliferation and maturation. A major gap in our understanding is the identity of the gene encoding a zebrafish Amh receptor; we show here that the loss of amhr2 is associated with the breakpoint of a chromosome rearrangement shared among cyprinid fishes.

In Vivo Ablation of the Conserved GATA-Binding Motif in the Amh Promoter Impairs Amh Expression in the Male Mouse

GATA4 is an essential transcriptional regulator required for gonadal development, differentiation, and function. In the developing testis, proposed GATA4-regulated genes include steroidogenic factor 1 (Nr5a1), SRY-related HMG box 9 (Sox9), and anti-Müllerian hormone (Amh). Although some of these genes have been validated as genuine GATA4 targets, it remains unclear whether GATA4 is a direct regulator of endogenous Amh transcription. We used a CRISPR/Cas9-based approach to specifically inactivate or delete the sole GATA-binding motif of the proximal mouse Amh promoter. AMH mRNA and protein levels were assessed at developmental time points corresponding to elevated AMH levels: fetal and neonate testes in males and adult ovaries in females. In males, loss of GATA binding to the Amh promoter significantly reduced Amh expression. Although the loss of GATA binding did not block the initiation of Amh transcription, AMH mRNA and protein levels failed to upregulate in the developing fetal and neonate testis. Interestingly, adult male mice presented no anatomical anomalies and had no evidence of retained Müllerian duct structures, suggesting that AMH levels, although markedly reduced, were sufficient to masculinize the male embryo. In contrast to males, GATA binding to the Amh promoter was dispensable for Amh expression in the adult ovary. These results provide conclusive evidence that in males, GATA4 is a positive modulator of Amh expression that works in concert with other key transcription factors to ensure that the Amh gene is sufficiently expressed in a correct spatiotemporal manner during fetal and prepubertal testis development.

The Battle of the Sexes: Human Sex Development and Its Disorders

The process of sexual differentiation is central for reproduction of almost all metazoan and therefore for maintenance of practically all multicellular organisms. In sex development we can distinguish two different processes: First, sex determination is the developmental decision that directs the undifferentiated embryo into a sexually dimorphic individual. In mammals, sex determination equals gonadal development. The second process known as sex differentiation takes place once the sex determination decision has been made through factors produced by the gonads that determine the development of the phenotypic sex. Most of the knowledge on the factors involved in sexual development came from animal models and from studies of cases in whom the genetic or the gonadal sex does not match the phenotypical sex, i.e., patients affected by disorders of sex development (DSD). Generally speaking, factors influencing sex determination are transcriptional regulators, whereas factors important for sex differentiation are secreted hormones and their receptors. This review focuses on the factors involved in gonadal determination, and whenever possible, references on the "prismatic" clinical cases are given.

Regulation of male sex determination: genital ridge formation and Sry activation in mice

Sex determination is essential for the sexual reproduction to generate the next generation by the formation of functional male or female gametes. In mammals, primary sex determination is commenced by the presence or absence of the Y chromosome, which controls the fate of the gonadal primordium. The somatic precursor of gonads, the genital ridge is formed at the mid-gestation stage and gives rise to one of two organs, a testis or an ovary. The fate of the genital ridge, which is governed by the differentiation of somatic cells into Sertoli cells in the testes or granulosa cells in the ovaries, further determines the sex of an individual and their germ cells. Mutation studies in human patients with disorders of sex development and mouse models have revealed factors that are involved in mammalian sex determination. In most of mammals, a single genetic trigger, the Y-linked gene Sry (sex determination region on Y chromosome), regulates testicular differentiation. Despite identification of Sry in 1990, precise mechanisms underlying the sex determination of bipotential genital ridges are still largely unknown. Here, we review the recent progress that has provided new insights into the mechanisms underlying genital ridge formation as well as the regulation of Sry expression and its functions in male sex determination of mice.

Mammalian sex determination—insights from humans and mice

Disorders of sex development (DSD) are congenital conditions in which the development of chromosomal, gonadal, or anatomical sex is atypical. Many of the genes required for gonad development have been identified by analysis of DSD patients. However, the use of knockout and transgenic mouse strains have contributed enormously to the study of gonad gene function and interactions within the development network. Although the genetic basis of mammalian sex determination and differentiation has advanced considerably in recent years, a majority of 46,XY gonadal dysgenesis patients still cannot be provided with an accurate diagnosis. Some of these unexplained DSD cases may be due to mutations in novel DSD genes or genomic rearrangements affecting regulatory regions that lead to atypical gene expression. Here, we review our current knowledge of mammalian sex determination drawing on insights from human DSD patients and mouse models.

Friend of GATA suppresses the GATA-induced transcription of hepcidin in hepatocytes through a GATA-regulatory element in the HAMP promoter

Hepcidin is an antimicrobial peptide hormone involved in the metabolism of iron, encoded for by the HAMP gene mainly in hepatocytes. It's expressed at lower levels in other cells such as the macrophages. The mechanisms that determine tissue-specific expression of hepcidin remain unclear. GATA- and its co-factor Friend of GATA (FOG) modulate the tissue-specific transcription of other genes involved in the metabolism of iron. GATA proteins are group of evolutionary conserved transcriptional regulators that bind to the consensus motif -WGATAR- in the promoter. We characterized a 1.3 kb fragment of the 5'-flanking sequence of the HAMP gene in Huh7 cells, which express HAMP. Transfection of 5'-deletions of the HAMP promoter in Huh7 cells revealed two regions, -932/-878 and -155/-96, that when deleted decreased promoter activity. Using site-directed mutations in the HAMP promoter region -155/-96 we identified two subregions, -138/-125 and -103/-98, which when mutated suppressed promoter activity by 70 and 90% respectively. Site -103/-98 with a sequence -TTATCT- to which endogenous GATA proteins 4 and 6 bind and transactivate HAMP is a GATA-regulatory element (RE). Mutation of the GATA-RE abrogated binding of GATA proteins 4 and 6 to the promoter and blunted the GATA transactivation of HAMP. FOG proteins 1 and 2 suppressed the endogenous and exogenous GATA activation of the HAMP promoter. We concluded that the GATA-RE, -TTATCT- in the HAMP promoter region -103/-98 is crucial for the GATA-4 and GATA-6 driven transcription of hepcidin in Huh7 cells and that FOG proteins moderate the transcription by suppressing the GATA transactivation of HAMP.

Mutation analysis of NR5A1 encoding steroidogenic factor 1 in 77 patients with 46, XY disorders of sex development (DSD) including hypospadias

Background

Mutations of the NR5A1 gene encoding steroidogenic factor-1 have been reported in association with a wide spectrum of 46,XY DSD (Disorder of Sex Development) phenotypes including severe forms of hypospadias.

Methodology/Principal Findings

We evaluated the frequency of NR5A1 gene mutations in a large series of patients presenting with 46,XY DSD and hypospadias. Based on their clinical presentation 77 patients were classified either as complete or partial gonadal dysgenesis (uterus seen at genitography and/or surgery, n = 11), ambiguous external genitalia without uterus (n = 33) or hypospadias (n = 33). We identified heterozygous NR5A1 mutations in 4 cases of ambiguous external genitalia without uterus (12.1%; p.Trp279Arg, pArg39Pro, c.390delG, c140_141insCACG) and a de novo missense mutation in one case with distal hypospadias (3%; p.Arg313Cys). Mutant proteins showed reduced transactivation activity and mutants p.Arg39Pro and p.Arg313Cys did not synergize with the GATA4 cofactor to stimulate reporter gene activity, although they retained their ability to physically interact with the GATA4 protein.

Conclusions/Significance

Mutations in NR5A1 were observed in 5/77 (6.5%) cases of 46,XY DSD including hypospadias. Excluding the cases of 46,XY gonadal dysgenesis the incidence of NR5A1 mutations was 5/66 (7.6%). An individual with isolated distal hypopadias carried a de novo heterozygous missense mutation, thus extending the range of phenotypes associated with NR5A1 mutations and suggesting that this group of patients should be screened for NR5A1 mutations.

Loss-of-function mutation in GATA4 causes anomalies of human testicular development

Approximately 1 of every 250 newborns has some abnormality of genital and/or gonadal development. However, a specific molecular cause is identified in only 20% of these cases of disorder of sex development (DSD). We identified a family of French origin presenting with 46,XY DSD and congenital heart disease. Sequencing of the ORF of GATA4 identified a heterozygous missense mutation (p.Gly221Arg) in the conserved N-terminal zinc finger of GATA4. This mutation was not observed in 450 ancestry-matched control individuals. The mutation compromised the ability of the protein to bind to and transactivate the anti-Müllerian hormone (AMH) promoter. The mutation does not interfere with the direct protein-protein interaction, but it disrupts synergistic activation of the AMH promoter by GATA4 and NR5A1. The p.Gly221Arg mutant protein also failed to bind to a known protein partner FOG2 that is essential for gonad formation. Our data demonstrate the key role of GATA4 in human testicular development.

A GATA4/WT1 cooperation regulates transcription of genes required for mammalian sex determination and differentiation

Background

In mammals, sex determination is genetically controlled. The SRY gene, located on Y chromosome, functions as the dominant genetic switch for testis development. The SRY gene is specifically expressed in a subpopulation of somatic cells (pre-Sertoli cells) of the developing urogenital ridge for a brief period during gonadal differentiation. Despite this tight spatiotemporal expression pattern, the molecular mechanisms that regulate SRY transcription remain poorly understood. Sry expression has been shown to be markedly reduced in transgenic mice harboring a mutant GATA4 protein (a member of the GATA family of transcription factors) disrupted in its ability to interact with its transcriptional partner FOG2, suggesting that GATA4 is involved in SRY gene transcription.

Results

Although our results show that GATA4 directly targets the pig SRY promoter, we did not observe similar action on the mouse and human SRY promoters. In the mouse, Wilms' tumor 1 (WT1) is an important regulator of both Sry and Müllerian inhibiting substance (Amh/Mis) expression and in humans, WT1 mutations are associated with abnormalities of sex differentiation. GATA4 transcriptionally cooperated with WT1 on the mouse, pig, and human SRY promoters. Maximal GATA4/WT1 synergism was dependent on WT1 but not GATA4 binding to their consensus regulatory elements in the SRY promoter and required both the zinc finger and C-terminal regions of the GATA4 protein. Although both isoforms of WT1 synergized with GATA4, synergism was stronger with the +KTS rather than the -KTS isoform. WT1/GATA4 synergism was also observed on the AMH promoter. In contrast to SRY, WT1/GATA4 action on the mouse Amh promoter was specific for the -KTS isoform and required both WT1 and GATA4 binding.

Conclusion

Our data therefore provide new insights into the molecular mechanisms that contribute to the tissue-specific expression of the SRY and AMH genes in both normal development and certain syndromes of abnormal sex differentiation.

Role of the GATA family of transcription factors in endocrine development, function, and disease

The WGATAR motif is a common nucleotide sequence found in the transcriptional regulatory regions of numerous genes. In vertebrates, these motifs are bound by one of six factors (GATA1 to GATA6) that constitute the GATA family of transcriptional regulatory proteins. Although originally considered for their roles in hematopoietic cells and the heart, GATA factors are now known to be expressed in a wide variety of tissues where they act as critical regulators of cell-specific gene expression. This includes multiple endocrine organs such as the pituitary, pancreas, adrenals, and especially the gonads. Insights into the functional roles played by GATA factors in adult organ systems have been hampered by the early embryonic lethality associated with the different Gata-null mice. This is now being overcome with the generation of tissue-specific knockout models and other knockdown strategies. These approaches, together with the increasing number of human GATA-related pathologies have greatly broadened the scope of GATA-dependent genes and, importantly, have shown that GATA action is not necessarily limited to early development. This has been particularly evident in endocrine organs where GATA factors appear to contribute to the transcription of multiple hormone-encoding genes. This review provides an overview of the GATA family of transcription factors as they relate to endocrine function and disease.