Failure of SOX9 regulation in 46XY disorders of sex development with SRY, SOX9 and SF1 mutations

SOX Genes and Their Role in Disorders of Sex Development

SOX genesare master regulatory genes controlling development and are fundamental to the establishment of sex determination in a multitude of organisms. The discovery of the master sex-determining gene SRY in 1990 was pivotal for the understanding of how testis development is initiated in mammals. With this discovery, an entire family of SOX factors were uncovered that play crucial roles in cell fate decisions during development. The importance of SOX genes in human reproductive development is evident from the various disorders of sex development (DSD) upon loss or overexpression of SOX gene function. Here, we review the roles that SOX genes play in gonad development and their involvement in DSD. We start with an overview of sex determination and differentiation, DSDs, and the SOX gene family and function. We then provide detailed information and discussion on SOX genes that have been implicated in DSDs, both at the gene and regulatory level. These include SRY, SOX9, SOX3, SOX8, and SOX10. This review provides insights on the crucial balance of SOX gene expression levels needed for gonad development and maintenance and how changes in these levels can lead to DSDs.

Tenuous Transcriptional Threshold of Human Sex Determination. I. SRY and Swyer Syndrome at the Edge of Ambiguity

Male sex determination in mammals is initiated by SRY, a Y-encoded transcription factor. The protein contains a high-mobility-group (HMG) box mediating sequence-specific DNA bending. Mutations causing XY gonadal dysgenesis (Swyer syndrome) cluster in the box and ordinarily arise de novo. Rare inherited variants lead to male development in one genetic background (the father) but not another (his sterile XY daughter). De novo and inherited mutations occur at an invariant Tyr adjoining the motif's basic tail (box position 72; Y127 in SRY). In SRY-responsive cell lines CH34 and LNCaP, de novo mutations Y127H and Y127C reduced SRY activity (as assessed by transcriptional activation of principal target gene Sox9) by 5- and 8-fold, respectively. Whereas Y127H impaired testis-specific enhancer assembly, Y127C caused accelerated proteasomal proteolysis; activity was in part rescued by proteasome inhibition. Inherited variant Y127F was better tolerated: its expression was unperturbed, and activity was reduced by only twofold, a threshold similar to other inherited variants. Biochemical studies of wild-type (WT) and variant HMG boxes demonstrated similar specific DNA affinities (within a twofold range), with only subtle differences in sharp DNA bending as probed by permutation gel electrophoresis and fluorescence resonance-energy transfer (FRET); thermodynamic stabilities of the free boxes were essentially identical. Such modest perturbations are within the range of species variation. Whereas our cell-based findings rationalize the de novo genotype-phenotype relationships, a molecular understanding of inherited mutation Y127F remains elusive. Our companion study uncovers cryptic biophysical perturbations suggesting that the para-OH group of Y127 anchors a novel water-mediated DNA clamp.

A conserved function of Human DLC3 and Drosophila Cv-c in testis development

The identification of genes affecting gonad development is essential to understand the mechanisms causing Variations/Differences in Sex Development (DSD). Recently, a DLC3 mutation was associated with male gonadal dysgenesis in 46,XY DSD patients. We have studied the requirement of Cv-c, the Drosophila ortholog of DLC3, in Drosophila gonad development, as well as the functional capacity of DLC3 human variants to rescue cv-c gonad defects. We show that Cv-c is required to maintain testis integrity during fly development. We find that Cv-c and human DLC3 can perform the same function in fly embryos, as flies carrying wild type but not patient DLC3 variations can rescue gonadal dysgenesis, suggesting functional conservation. We also demonstrate that the StART domain mediates Cv-c's function in the male gonad independently from the GAP domain's activity. This work demonstrates a role for DLC3/Cv-c in male gonadogenesis and highlights a novel StART domain mediated function required to organize the gonadal mesoderm and maintain its interaction with the germ cells during testis development.

A novel variant of NR5A1, p.R350W implicates potential interactions with unknown co-factors or ligands

INTRODUCTION

NR5A1 and NR5A2 belong to an orphan nuclear receptor group, and approximately 60% of their amino acid sequences are conserved. Transcriptional regulation of NR5A receptors depends on interactions with co-factors or unidentified ligands.

PURPOSE AND METHODS

We employed in vitro and in silico analysis for elucidating the pathophysiology of a novel variant in the ligand-binding domain of NR5A1, p.R350W which was identified from a 46,XY patient with atypical genitalia.

RESULTS

In the study, [1] reporter assays demonstrated that R350 is essential for NR5A1; [2] 3D model analysis predicted that R350 interacted with endogenous ligands or unknown cofactors rather than stabilizing the structure; [3] R350 is not conserved in NR5A2 but is specifically required for NR5A1; and [4] none of the 22 known missense variants of the ligand binding domain satisfied all the previous conditions [1]-[3], suggesting the unique role of R350 in NR5A1.

CONCLUSION

Our data suggest that NR5A1 has unidentified endogenous ligands or co-activators that selectively potentiate the transcriptional function of NR5A1 in vivo.

Targeting the Non-Coding Genome for the Diagnosis of Disorders of Sex Development

Disorders of sex development (DSD) are a complex group of conditions with highly variable clinical phenotypes, most often caused by failure of gonadal development. DSD are estimated to occur in around 1.7% of all live births. Whilst the understanding of genes involved in gonad development has increased exponentially, approximately 50% of patients with a DSD remain without a genetic diagnosis, possibly implicating non-coding genomic regions instead. Here, we review how variants in the non-coding genome of DSD patients can be identified using techniques such as array comparative genomic hybridization (CGH) to detect copy number variants (CNVs), and more recently, whole genome sequencing (WGS). Once a CNV in a patient's non-coding genome is identified, putative regulatory elements such as enhancers need to be determined within these vast genomic regions. We will review the available online tools and databases that can be used to refine regions with potential enhancer activity based on chromosomal accessibility, histone modifications, transcription factor binding site analysis, chromatin conformation, and disease association. We will also review the current in vitro and in vivo techniques available to demonstrate the functionality of the identified enhancers. The review concludes with a clinical update on the enhancers linked to DSD.

Oestrogen Activates the MAP3K1 Cascade and β-Catenin to Promote Granulosa-like Cell Fate in a Human Testis-Derived Cell Line

Sex determination triggers the differentiation of the bi-potential gonad into either an ovary or testis. In non-mammalian vertebrates, the presence or absence of oestrogen dictates gonad differentiation, while in mammals, this mechanism has been supplanted by the testis-determining gene SRY. Exogenous oestrogen can override this genetic trigger to shift somatic cell fate in the gonad towards ovarian developmental pathways by limiting the bioavailability of the key testis factor SOX9 within somatic cells. Our previous work has implicated the MAPK pathway in mediating the rapid cellular response to oestrogen. We performed proteomic and phosphoproteomic analyses to investigate the precise mechanism through which oestrogen impacts these pathways to activate β-catenin-a factor essential for ovarian development. We show that oestrogen can activate β-catenin within 30 min, concomitant with the cytoplasmic retention of SOX9. This occurs through changes to the MAP3K1 cascade, suggesting this pathway is a mechanism through which oestrogen influences gonad somatic cell fate. We demonstrate that oestrogen can promote the shift from SOX9 pro-testis activity to β-catenin pro-ovary activity through activation of MAP3K1. Our findings define a previously unknown mechanism through which oestrogen can promote a switch in gonad somatic cell fate and provided novel insights into the impacts of exogenous oestrogen exposure on the testis.

Towards improved genetic diagnosis of human differences of sex development

Despite being collectively among the most frequent congenital developmental conditions worldwide, differences of sex development (DSD) lack recognition and research funding. As a result, what constitutes optimal management remains uncertain. Identification of the individual conditions under the DSD umbrella is challenging and molecular genetic diagnosis is frequently not achieved, which has psychosocial and health-related repercussions for patients and their families. New genomic approaches have the potential to resolve this impasse through better detection of protein-coding variants and ascertainment of under-recognized aetiology, such as mosaic, structural, non-coding or epigenetic variants. Ultimately, it is hoped that better outcomes data, improved understanding of the molecular causes and greater public awareness will bring an end to the stigma often associated with DSD.

A novel SRY pathogenic variant from a 46,XY female harboring a nonsense point mutation (G to A) in position 293

46,XY female is a genetic disorder characterized by gonad gender not consistent with chromosomal sex. The SRY gene mutation is a common cause of 46,XY reversal type 1 (OMIM: 400044). Peripheral blood was collected from a 46,XY female patient and her father. Sex chromosomes were confirmed by karyotype analysis and fluorescence in situ hybridization (FISH) detection of the specific probe of sex chromosomes with cultured lymphocytes. After extracting blood genomic DNA, SRY characteristic fluorescence peak was detected by quantitative fluorescence PCR (QF-PCR) method. Whole exome was sequenced with NGS, and SRY gene was sequenced by Sanger sequencing, respectively. The chromosomes X and Y of the patient were confirmed by karyotype of 46,XY, and FISH specific probe of chromosome X and Y. SRY specific fluorescence peak was observed by QF-PCR. The whole-exome sequencing results showed chrY: 2655352(GRCh37): c.293G>A hemizygote mutation, confirmed by Sanger sequencing. The de novo mutation resulted in the mRNA encoding the tryptophan codon of 98 (UGG) change into a termination codon (UAG) (P.Trp98ter), and the translation process was terminated prematurely. The discovery of this novel mutation in the SRY gene helps elucidate the molecular mechanism of 46,XY female sex reversal and enriches such patients' genetic mutation spectrum.

A missense mutation (c.226C>A) in HMG box SRY gene affects nNLS function in 46,XY sex reversal female

The SRY initiates cascade of gene expression that transforms the undifferentiated gonad, genital ridge into testis. Mutations of the SRY gene is associated with complete gonadal dysgenesis in females with 46,XY karyotype. Primary amenorrhea is one of the clinical findings to express the genetic cause in 46,XY sex reversal. Here, we report a 26-year-old married woman presenting with primary amenorhea and complete gonadal dysgenesis. The clinical phenotypes were hypoplastic uterus with streak gonad and underdeveloped secondary sexual characters. The cytogenetic analysis confirmed 46,XY sex reversal karyotype of a female. Using molecular approach, we screened open reading frame of the SRY gene by PCR and targeted DNA Sanger sequencing. The patient was confirmed with nucleotide substitution (c.226C>A; p.Arg76Ser) at in HMG box domain of SRY gene that causes 46,XY sex reversal female. Mutation prediction algorithms suggest that alteration might be disease causing mutation and mutated (p.Arg76Ser) amino acid deleteriously affects HMG box nNLS region of SRY protein. Clinical phenotypes and in silico analysis confirmed that missense substitution (p.Arg76Ser) impaired nNLS binding Calmodulin-mediated nuclear transport of SRY from cytoplasm to nucleus. The mutation affects down regulation of male sex differentiation pathway and is responsible for 46,XY sex reversal female with gonadal dysgenesis.

Integrated mRNA and miRNA expression profile analysis of female and male gonads in Hyriopsis cumingii

Hyriopsis cumingii is an important species for freshwater pearl cultivation in China. In terms of pearl production, males have larger pearls and better glossiness than females, but there are few reports focusing on the sex of H. cumingii. In this study, six mRNA and six microRNA (miRNA) libraries were prepared from ovaries and testes. Additionally, 28,502 differentially expressed genes (DEGs) and 32 differentially expressed miRNAs (DEMs) were identified. Compared with testis, 14,360 mRNAs and 20 miRNAs were up-regulated in ovary, 14,142 mRNAs and 12 miRNAs were down-regulated. In DEGs, the known genes related to sex determinism and/or differentiation were also identified, such as DMRT1, SOX9, SF1 for males, FOXL2 for females, and other potentially significant candidate genes. Three sex-related pathways have also been identified, which are Wnt, Notch, and TGF-beta. In 32 DEMs, the three miRNAs (miR-9-5p, miR-92, miR-184) were paid more attention, they predicted 28 target genes, which may also be candidates for sex-related miRNAs and genes. Differential miRNAs target genes analysis reveals the pathway associated with oocyte meiosis and spermatogenesis. Overall, the findings of the study provide significant insights to enhance our understanding of sex differentiation and/or sex determination mechanisms for H. cumingii.

Identification and functional analysis of fourteen NR5A1 variants in patients with the 46 XY disorders of sex development

Human sex determination and differentiation is a complex process, during which NR5A1 plays a central role via the transcriptional regulation of key modulators involved in steroidogenesis. Approximately 8-15% of 46,XY DSD are caused by variants in the NR5A1 gene. Therefore, screening for variants in the NR5A1 gene was performed in a Chinese cohort of sixty-two 46,XY DSD patients with no AR or SRD5A2 variants via next-generation sequencing (NGS). Fourteen variants in the NR5A1 gene were identified in 16 patients from 14 unrelated families, including nine novel variants. These variants included eight heterozygote missense variants, two heterozygote frameshift variants, two heterozygote nonsense variants, one heterozygote nonframeshift deletion-insertion variant, and one homozygous missense variant. Functional assays showed that the transcriptional activity of the 11 variants was significantly reduced. In this study, 11 NR5A1 pathogenic variants were identified. These novel variants further expand the existing spectrum of the NR5A1 variants associated with 46,XY DSD, which will, in turn, assist in the molecular diagnosis of DSD.

Estrogen suppresses SOX9 and activates markers of female development in a human testis-derived cell line

Background

The increasing incidence of reproductive disorders in humans has been attributed to in utero exposure to estrogenic endocrine disruptors. In particular, exposure of the developing testis to exogenous estrogen can negatively impact male reproductive health. To determine how estrogens impact human gonad function, we treated the human testis-derived cell line NT2/D1 with estrogen and examined its impact on SOX9 and the expression of key markers of granulosa (ovarian) and Sertoli (testicular) cell development.

Results

Estrogen successfully activated its cognate receptor (estrogen receptor alpha; ESR1) in NT2/D1 cells. We observed a significant increase in cytoplasmic SOX9 following estrogen treatment. After 48 h of estrogen exposure, mRNA levels of the key Sertoli cell genes SOX9, SRY, AMH, FGF9 and PTGDS were significantly reduced. This was followed by a significant increase in mRNA levels for the key granulosa cell genes FOXL2 and WNT4 after 96 h of estrogen exposure.

Conclusions

These results are consistent with estrogen's effects on marsupial gonads and show that estrogen has a highly conserved impact on gonadal cell fate decisions that has existed in mammals for over 160 million years. This effect of estrogen presents as a potential mechanism contributing to the significant decrease in male fertility and reproductive health reported over recent decades. Given our widespread exposure to estrogenic endocrine disruptors, their effects on SOX9 and Sertoli cell determination could have considerable impact on the adult testis.

Applying Single-Cell Analysis to Gonadogenesis and DSDs (Disorders/Differences of Sex Development)

The gonads are unique among the body's organs in having a developmental choice: testis or ovary formation. Gonadal sex differentiation involves common progenitor cells that form either Sertoli and Leydig cells in the testis or granulosa and thecal cells in the ovary. Single-cell analysis is now shedding new light on how these cell lineages are specified and how they interact with the germline. Such studies are also providing new information on gonadal maturation, ageing and the somatic-germ cell niche. Furthermore, they have the potential to improve our understanding and diagnosis of Disorders/Differences of Sex Development (DSDs). DSDs occur when chromosomal, gonadal or anatomical sex are atypical. Despite major advances in recent years, most cases of DSD still cannot be explained at the molecular level. This presents a major pediatric concern. The emergence of single-cell genomics and transcriptomics now presents a novel avenue for DSD analysis, for both diagnosis and for understanding the molecular genetic etiology. Such -omics datasets have the potential to enhance our understanding of the cellular origins and pathogenesis of DSDs, as well as infertility and gonadal diseases such as cancer.

High Molecular Diagnosis Rate in Undermasculinized Males with Differences in Sex Development Using a Stepwise Approach

Differences of sex development (DSDs) are a constellation of conditions that result in genital ambiguity or complete sex reversal. Although determining the underlying genetic variants can affect clinical management, fewer than half of undermasculinized males ever receive molecular diagnoses. Next-generation sequencing (NGS) technology has improved diagnostic capabilities in several other diseases, and a few small studies suggest that it may improve molecular diagnostic capabilities in DSDs. However, the overall diagnostic rate that can be achieved with NGS for larger groups of patients with DSDs remains unknown. In this study, we aimed to implement a tiered approach to genetic testing in undermasculinized males seen in an interdisciplinary DSD clinic to increase the molecular diagnosis rate in this group. We determined the diagnosis rate in patients undergoing all clinically available testing. Patients underwent a stepwise approach to testing beginning with a karyotype and progressing through individual gene testing, microarray, panel testing, and then to whole-exome sequencing (WES) if no molecular cause was found. Deletion/duplication studies were also done if deletions were suspected. Sixty undermasculinized male participants were seen in an interdisciplinary DSD clinic from 2008 to 2016. Overall, 37/60 (62%) of patients with Y chromosomes and 46% of those who were 46XY received molecular diagnoses. Of the 46,XY patients who underwent all available genetic testing, 18/28 (64%) achieved molecular diagnoses. This study suggests that the addition of WES testing can result in a higher rate of molecular diagnoses compared to genetic panel testing.

Disorders of Sexual Development: Current Status and Progress in the Diagnostic Approach

Disorders of sexual development (DSD) are conditions with an atypical chromosomal, gonadal or phenotypic sex, which leads to differences in the development of the urogenital tract and different clinical phenotypes. Some genes have been implicated in the sex development during gonadal and functional differentiation where the maintenance of the somatic sex of the gonad as either male or female is achieved by suppression of the alternate route. The diagnosis of DSD requires a structured approach, involving a multidisciplinary team and different molecular techniques. We discuss the dimorphic genes and the specific pathways involved in gonadal differentiation, as well as new techniques for genetic analysis and their diagnostic value including epigenetic mechanisms, expanding the evidence in the diagnostic approach of individuals with DSD to increase knowledge of the etiology.

Mutant NR5A1/SF-1 in patients with disorders of sex development shows defective activation of the SOX9 TESCO enhancer

Nuclear receptor subfamily 5 group A member 1/Steroidogenic factor 1 (NR5A1; SF-1; Ad4BP) mutations cause 46,XY disorders of sex development (DSD), with phenotypes ranging from developmentally mild (e.g., hypospadias) to severe (e.g., complete gonadal dysgenesis). The molecular mechanism underlying this spectrum is unclear. During sex determination, SF-1 regulates SOX9 (SRY [sex determining region Y]-box 9) expression. We hypothesized that SF-1 mutations in 46,XY DSD patients affect SOX9 expression via the Testis-specific Enhancer of Sox9 core element, TESCO. Our objective was to assess the ability of 20 SF-1 mutants found in 46,XY DSD patients to activate TESCO. Patient DNA was sequenced for SF-1 mutations and mutant SF-1 proteins were examined for transcriptional activity, protein expression, sub-cellular localization and in silico structural defects. Fifteen of the 20 mutants showed reduced SF-1 activation on TESCO, 11 with atypical sub-cellular localization. Fourteen SF-1 mutants were predicted in silico to alter DNA, ligand or cofactor interactions. Our study may implicate aberrant SF-1-mediated transcriptional regulation of SOX9 in 46,XY DSDs.

The evolutionary process of mammalian sex determination genes focusing on marsupial SRYs

BACKGROUND

Maleness in mammals is genetically determined by the Y chromosome. On the Y chromosome SRY is known as the mammalian male-determining gene. Both placental mammals (Eutheria) and marsupial mammals (Metatheria) have SRY genes. However, only eutherian SRY genes have been empirically examined by functional analyses, and the involvement of marsupial SRY in male gonad development remains speculative.

RESULTS

In order to demonstrate that the marsupial SRY gene is similar to the eutherian SRY gene in function, we first examined the sequence differences between marsupial and eutherian SRY genes. Then, using a parsimony method, we identify 7 marsupial-specific ancestral substitutions, 13 eutherian-specific ancestral substitutions, and 4 substitutions that occurred at the stem lineage of therian SRY genes. A literature search and molecular dynamics computational simulations support that the lineage-specific ancestral substitutions might be involved with the functional differentiation between marsupial and eutherian SRY genes. To address the function of the marsupial SRY gene in male determination, we performed luciferase assays on the testis enhancer of Sox9 core (TESCO) using the marsupial SRY. The functional assay shows that marsupial SRY gene can weakly up-regulate the luciferase expression via TESCO.

CONCLUSIONS

Despite the sequence differences between the marsupial and eutherian SRY genes, our functional assay indicates that the marsupial SRY gene regulates SOX9 as a transcription factor in a similar way to the eutherian SRY gene. Our results suggest that SRY genes obtained the function of male determination in the common ancestor of Theria (placental mammals and marsupials). This suggests that the marsupial SRY gene has a function in male determination, but additional experiments are needed to be conclusive.

Why boys will be boys and girls will be girls: Human sex development and its defects

Among the most defining events of an individual's life, is the development of a human embryo into male or a female. The phenotypic sex of an individual depends on the type of gonad that develops in the embryo, a process which itself is determined by the genetic setting of the individual. The development of the gonads is different from any other organ, as they possess the potential to differentiate into two functionally distinct organs, testes, or ovaries. Sex development can be divided into two distinctive processes, "sex determination," which is the commitment of the undifferentiated gonad into either a testis or an ovary, a process that is genetically programmed in a critically timed manner and "sex differentiation," which takes place through hormones produced by the gonads, once the developmental sex determination decision has been made. Disruption of any of the genes involved in either the testicular or ovarian development pathway could lead to disorders of sex development. In this review, we provide an insight into the factors important for sex determination, their antagonistic actions and whenever possible, references on the "prismatic" clinical cases are given. Birth Defects Research (Part C) 108:365-379, 2016. © 2016 Wiley Periodicals, Inc.

Altered SOX9 genital tubercle enhancer region in hypospadias

Human mutations in the SOX9 gene or its regulatory region can disrupt testicular development, leading to disorders of sex development (DSDs). Our previous work involving the genomic analysis of isolated DSD patients revealed a 78kb minimal sex determining region (RevSex) far upstream of SOX9 that was duplicated in 46,XX and deleted in 46,XY DSDs. It was postulated that RevSex contains a gonadal enhancer. However, the most highly conserved sub-region within RevSex, called SR4, was neither responsive to sex determining factors in vitro nor active in the gonads of transgenic mice, suggesting that SR4 may not be functioning as a testicular enhancer. Interestingly, SR4 transgenic mice showed reporter activity in the genital tubercle, the primordium of the penis and clitoris, a previously unreported domain of Sox9 expression. SOX9 protein was detected in the genital tubercle, notably in the urethral plate epithelium, preputial glands, ventral surface ectoderm and corpus cavernosa. SR4 may therefore function as a Sox9 genital tubercle enhancer, mutations of which could possibly lead to hypospadias, a birth defect seen in the DSD patients in the RevSex study. SR4 activity and the observed SOX9 expression pattern suggest that SR4 may function as a Sox9 genital tubercle enhancer. However, conditional ablation of Sox9 in the genital tubercle using Shh-Cre/+;Sox9^flox/flox mice revealed no genital tubercle abnormalities, possibly due to compensation by similar Sox factors. To conclude, we have identified a novel regulatory enhancer driving Sox9 expression during external genitalia development.

A Case with late onset of ambiguous genitalia

BACKGROUND

Ambiguous genitalia is an uncommon situation that happens between 1 and 2 per every 1000 live births and falls under the umbrella diagnosis of disorders of sexual development.

CASE

In this article, we report a case of male pseudohermaphroditism with ambiguous genitalia. The proband was a 12 yr old girl without any uterus or ovarian tissues. Karyotype of the case is 46, XY. Genes involved in sexual differentiation such as AR, SRD5A2, LH, LHR, FSH, 17 B HSD and SRY genes were sequenced in both directions. No mutations were found in these genes either.

CONCLUSION

It seems advisable to be cautious in similar cases, and revise protocol for tracing the genes involved in the patients.

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.

Human Sex Determination at the Edge of Ambiguity: INHERITED XY SEX REVERSAL DUE TO ENHANCED UBIQUITINATION AND PROTEASOMAL DEGRADATION OF A MASTER TRANSCRIPTION FACTOR

A general problem is posed by analysis of transcriptional thresholds governing cell fate decisions in metazoan development. A model is provided by testis determination in therian mammals. Its key step, Sertoli cell differentiation in the embryonic gonadal ridge, is initiated by SRY, a Y-encoded architectural transcription factor. Mutations in human SRY cause gonadal dysgenesis leading to XY female development (Swyer syndrome). Here, we have characterized an inherited mutation compatible with either male or female somatic phenotypes as observed in an XY father and XY daughter, respectively. The mutation (a crevice-forming substitution at a conserved back surface of the SRY high mobility group box) markedly destabilizes the domain but preserves specific DNA affinity and induced DNA bend angle. On transient transfection of diverse human and rodent cell lines, the variant SRY exhibited accelerated proteasomal degradation (relative to wild type) associated with increased ubiquitination; in vitro susceptibility to ubiquitin-independent ("default") cleavage by the 20S core proteasome was unchanged. The variant's gene regulatory activity (as assessed in a cellular model of the rat embryonic XY gonadal ridge) was reduced by 2-fold relative to wild-type SRY at similar levels of mRNA expression. Chemical proteasome inhibition restored native-like SRY expression and transcriptional activity in association with restored occupancy of a sex-specific enhancer element in principal downstream gene Sox9, demonstrating that the variant SRY exhibits essentially native activity on a per molecule basis. Our findings define a novel mechanism of impaired organogenesis, accelerated ubiquitin-directed proteasomal degradation of a master transcription factor leading to a developmental decision poised at the edge of ambiguity.

SOX9 regulates expression of the male fertility gene Ets variant factor 5 (ETV5) during mammalian sex development

In humans, dysregulation of the sex determining gene SRY-box 9 (SOX9) leads to disorders of sex development (DSD). In mice, knock-out of Sox9 prior to sex determination leads to XY sex reversal, while Sox9 inactivation after sex determination leads to spermatogenesis defects. SOX9 specifies the differentiation and function of Sertoli cells from somatic cell precursors, which then orchestrate the development and maintenance of other testicular cell types, largely through unknown mechanisms. Here, we describe a novel testicular target gene of SOX9, Ets variant factor 5 (ETV5), a transcription factor responsible for maintaining the spermatogonial stem cell niche. Etv5 was highly expressed in wild-type XY but not XX mouse fetal gonads, with ETV5 protein localized in the Sertoli cells, interstitial cells and germ cells of the testis. In XY Sox9 knock-out gonads, Etv5 expression was strongly down-regulated. Similarly, knock-down of SOX9 in the human Sertoli-like cell line NT2/D1 caused a decrease in ETV5 gene expression. Transcriptomic analysis of NT2/D1 cells over-expressing SOX9 showed that ETV5 expression was increased in response to SOX9. Moreover, chromatin immunoprecipitation of these cells, as well as of embryonic mouse gonads, showed direct binding of SOX9 to ETV5 regulatory regions. We demonstrate that SOX9 was able to activate ETV5 expression via a conserved SOX site in the 5' regulatory region, mutation of which led to loss of activation. In conclusion, we present a novel target gene of SOX9 in the testis, and suggest that SOX9 regulation of ETV5 contributes to the control of male fertility.

miR-138 suppresses cell proliferation and invasion by inhibiting SOX9 in hepatocellular carcinoma

Accumulating evidence suggests that miR-138 expression was frequently downregulated in different cancer types and involves in the progression of tumorigenesis. However, the biological role and molecular mechanism of miR-138 involvement in hepatocellular carcinoma (HCC) still remains largely unknown. Therefore, in the present study, we investigated the role of miR-138 in the progression of HCC. We found that miR-138 expression levels were significantly downregulated in HCC tissues and cell lines compared with the corresponding noncancerous liver tissues and normal hepatic cell line. In addition, we also found that enforced expression of miR-138 inhibited proliferation, colony formation, migration and invasion in HCC cells. Using a luciferase reporter assay, SOX9 was confirmed as a direct target of miR-138. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot assay showed that overexpression of miR-138 in HCC cells significantly inhibited SOX9 expression on mRNA level and protein level. Furthermore, SOX9 expression was significantly upregulated in HCC tissues and cell lines, and its mRNA expression is negative correlated with miR-138 expression in clinical HCC tissues (r=-0.689, P<0.01). Of note, downregulation of SOX9 performed similar effects with overexpression of miR-138. These findings suggested that miR-138 functioned as a tumor suppressor in HCC partially via repressing SOX9 expression.

Swyer syndrome

PURPOSE OF REVIEW

This review focuses on the pathogenesis, diagnosis, management and long-term outcomes of disorders of sex development, specifically women with Swyer syndrome (46,XY complete gonadal dysgenesis).

RECENT FINDINGS

Recent discoveries have broadened our understanding of the complex pathways involved in normal and abnormal sex development. In 46,XY gonadal dysgenesis, lack of testis development may be triggered by sex determining region Y, NR5A1, DHH or testis-determining gene loss-of-function mutations, DAX1 or WNT4 duplication or MAP3K1 gain-of-function mutations. The diagnosis and management of patients with Swyer syndrome is complex, and optimal care requires an experienced multidisciplinary team. Early diagnosis is vital because of the significant risk of germ cell tumour, and bilateral gonadectomy should be performed. Furthermore, early sex hormone treatment is necessary to induce and maintain typical pubertal development and to achieve optimal bone mineral accumulation. Pregnancy is possible via ova donation, and outcomes are similar to women with 46,XX ovarian failure.

SUMMARY

Further pathogenic gene mutations are likely to be identified, and the function, interaction and phenotypic effects of new and existing mutations will be further defined. Patients require long-term follow-up in specialist centres.

Structure-function relationships in human testis-determining factor SRY: an aromatic buttress underlies the specific DNA-bending surface of a high mobility group (HMG) box

Human testis determination is initiated by SRY, a Y-encoded architectural transcription factor. Mutations in SRY cause 46 XY gonadal dysgenesis with female somatic phenotype (Swyer syndrome) and confer a high risk of malignancy (gonadoblastoma). Such mutations cluster in the SRY high mobility group (HMG) box, a conserved motif of specific DNA binding and bending. To explore structure-function relationships, we constructed all possible substitutions at a site of clinical mutation (W70L). Our studies thus focused on a core aromatic residue (position 15 of the consensus HMG box) that is invariant among SRY-related HMG box transcription factors (the SOX family) and conserved as aromatic (Phe or Tyr) among other sequence-specific boxes. In a yeast one-hybrid system sensitive to specific SRY-DNA binding, the variant domains exhibited reduced (Phe and Tyr) or absent activity (the remaining 17 substitutions). Representative nonpolar variants with partial or absent activity (Tyr, Phe, Leu, and Ala in order of decreasing side-chain volume) were chosen for study in vitro and in mammalian cell culture. The clinical mutation (Leu) was found to markedly impair multiple biochemical and cellular activities as respectively probed through the following: (i) in vitro assays of specific DNA binding and protein stability, and (ii) cell culture-based assays of proteosomal degradation, nuclear import, enhancer DNA occupancy, and SRY-dependent transcriptional activation. Surprisingly, however, DNA bending is robust to this or the related Ala substitution that profoundly impairs box stability. Together, our findings demonstrate that the folding, trafficking, and gene-regulatory function of SRY requires an invariant aromatic "buttress" beneath its specific DNA-bending surface.

Gonad transcriptome analysis of pearl oyster Pinctada margaritifera: identification of potential sex differentiation and sex determining genes

BACKGROUND

Black pearl farming is based on culture of the blacklip pearl oyster Pinctada margaritifera (Mollusca, lophotrochozoa), a protandrous hermaphrodite species. At first maturation, all individuals are males. The female sex appears progressively from two years old, which represents a limitation for broodstock conditioning for aquaculture production. In marine mollusks displaying hermaphroditic features, data on sexual determinism and differentiation, including the molecular sex determining cascade, are scarce. To increase genomic resources and identify the molecular mechanisms whereby gene expression may act in the sexual dimorphism of P. margaritifera, we performed gonad transcriptome analysis.

RESULTS

The gonad transcriptome of P. margaritifera was sequenced from several gonadic samples of males and females at different development stages, using a Next-Generation-Sequencing method and RNAseq technology. After Illumina sequencing, assembly and annotation, we obtained 70,147 contigs of which 62.2% shared homologies with existing protein sequences, and 9% showed functional annotation with Gene Ontology terms. Differential expression analysis identified 1,993 differentially expressed contigs between the different categories of gonads. Clustering methods of samples revealed that the sex explained most of the variation in gonad gene expression. K-means clustering of differentially expressed contigs showed 815 and 574 contigs were more expressed in male and female gonads, respectively. The analysis of these contigs revealed the presence of known specific genes coding for proteins involved in sex determinism and/or differentiation, such as dmrt and fem-1 like for males, or foxl2 and vitellogenin for females. The specific gene expression profiles of pmarg-fem1-like, pmarg-dmrt and pmarg-foxl2 in different reproductive stages (undetermined, sexual inversion and regression) suggest that these three genes are potentially involved in the sperm-oocyte switch in P. margaritifera.

CONCLUSIONS

The study provides a new transcriptomic tool to study reproduction in hermaphroditic marine mollusks. It identifies sex differentiation and potential sex determining genes in P. margaritifera, a protandrous hermaphrodite species.

Disorders of sex development (DSDs): an update

CONTEXT

Disorders of sex development (DSDs) may arise from genetic defects in testis or ovary determination. Current analytical technologies and improved understanding of major regulatory pathways have cast new insight into the genetic basis for these disorders.

EVIDENCE ACQUISITION

A PubMed search was performed for the years 2011-13 using the terms "disorder of sex development," "gonadal dysgenesis," "ovarian dysgenesis," "array CGH," and "whole exome sequencing." Only articles from peer-reviewed journals were included.

EVIDENCE SYNTHESIS

Key themes that emerged included aberrant regulation of SOX9 via the hTES promoter in 46,XY gonadal DSDs, the role of the MAPK pathway in normal and aberrant gonadal development, and the role of new technologies in identification of gonadal DSDs.

CONCLUSIONS

With the advent of the robust new technologies of array comparative genomic hybridization and genomic sequencing in recent years, many new sex-determining genes have been identified. These genes have been organized into ovarian- and testicular-determining pathways that can block each other's activities. Identification of a mutation in a sex-determining gene in an individual affected with a DSD may warrant more extensive investigation for other phenotypic effects as well as genetic testing of other family members.

Testicular differentiation factor SF-1 is required for human spleen development

The transcription factor steroidogenic factor 1 (SF-1; also known as NR5A1) is a crucial mediator of both steroidogenic and nonsteroidogenic tissue differentiation. Mutations within SF1 underlie different disorders of sexual development (DSD), including sex reversal, spermatogenic failure, ovarian insufficiency, and adrenocortical deficiency. Here, we identified a recessive mutation within SF1 that resulted in a substitution of arginine to glutamine at codon 103 (R103Q) in a child with both severe 46,XY-DSD and asplenia. The R103Q mutation decreased SF-1 transactivation of TLX1, a transcription factor that has been shown to be essential for murine spleen development. Additionally, the SF1 R103Q mutation impaired activation of steroidogenic genes, without affecting synergistic SF-1 and sex-determining region Y (SRY) coactivation of the testis development gene SOX9. Together, our data provide evidence that SF-1 is required for spleen development in humans via transactivation of TLX1 and that mutations that only impair steroidogenesis, without altering the SF1/SRY transactivation of SOX9, can lead to 46,XY-DSD.

Chromosome conformation capture-on-chip analysis of long-range cis-interactions of the SOX9 promoter

Evolutionarily conserved transcription factor SOX9 is essential for the differentiation of chondrocytes and the development of testes. Heterozygous point mutations and genomic deletions involving SOX9 lead to campomelic dysplasia (CD), a skeletal malformation syndrome often associated with sex reversal. Chromosomal rearrangements with breakpoints mapping up to 1.6 Mb up- and downstream to SOX9, and likely disrupting its distant cis-regulatory elements, have been described in patients with milder forms of CD. Based on the location of these aberration breakpoints, four clusters upstream of SOX9 have been defined. Interestingly, we found that each of these intervals overlaps a gene encoding long noncoding RNA (lncRNA), suggesting that lncRNAs may contribute to long-range regulation of SOX9 expression. One of the four upstream regions, RevSex (517-595 kb 5' to SOX9), is associated with sex reversal, and was suggested to harbor a testis-specific and sex-determining enhancer. Another sex-determining interval was mapped to a gene desert >1.3 Mb downstream of SOX9. We have performed chromosome conformation capture-on-chip (4C) analysis in Sertoli cells and lymphoblasts to verify the proposed long-range interactions of the SOX9 promoter and to identify potential novel regulatory elements that might be responsible for sex reversal in patients with CD. We identified several novel potentially cis-interacting regions both up- and downstream to SOX9, with some of them overlapping lncRNA genes. Our data point to lncRNAs as likely mediators of some of these regulatory interactions.

Mutations in MAP3K1 tilt the balance from SOX9/FGF9 to WNT/β-catenin signaling

In-frame missense and splicing mutations (resulting in a 2 amino acid insertion or a 34 amino acid deletion) dispersed through the MAP3K1 gene tilt the balance from the male to female sex-determining pathway, resulting in 46,XY disorder of sex development. These MAP3K1 mutations mediate this balance by enhancing WNT/β-catenin/FOXL2 expression and β-catenin activity and by reducing SOX9/FGF9/FGFR2/SRY expression. These effects are mediated at multiple levels involving MAP3K1 interaction with protein co-factors and phosphorylation of downstream targets. In transformed B-lymphoblastoid cell lines and NT2/D1 cells transfected with wild-type or mutant MAP3K1 cDNAs under control of the constitutive CMV promoter, these mutations increased binding of RHOA, MAP3K4, FRAT1 and AXIN1 and increased phosphorylation of p38 and ERK1/2. Overexpressing RHOA or reducing expression of MAP3K4 in NT2/D1 cells produced phenocopies of the MAP3K1 mutations. Using siRNA knockdown of RHOA or overexpressing MAP3K4 in NT2/D1 cells produced anti-phenocopies. Interestingly, the effects of the MAP3K1 mutations were rescued by co-transfection with wild-type MAP3K4. Although MAP3K1 is not usually required for testis determination, mutations in this gene can disrupt normal development through the gains of function demonstrated in this study.

Inherited human sex reversal due to impaired nucleocytoplasmic trafficking of SRY defines a male transcriptional threshold

Human testis determination is initiated by SRY (sex determining region on Y chromosome). Mutations in SRY cause gonadal dysgenesis with female somatic phenotype. Two subtle variants (V60L and I90M in the high-mobility group box) define inherited alleles shared by an XY sterile daughter and fertile father. Whereas specific DNA binding and bending are unaffected in a rat embryonic pre-Sertoli cell line, the variants exhibited selective defects in nucleocytoplasmic shuttling due to impaired nuclear import (V60L; mediated by Exportin-4) or export (I90M; mediated by chromosome region maintenance 1). Decreased shuttling limits nuclear accumulation of phosphorylated (activated) SRY, in turn reducing occupancy of DNA sites regulating Sertoli-cell differentiation [the testis-specific SRY-box 9 (Sox9) enhancer]. Despite distinct patterns of biochemical and cell-biological perturbations, V60L and I90M each attenuated Sox9 expression in transient transfection assays by twofold. Such attenuation was also observed in studies of V60A, a clinical variant associated with ovotestes and hence ambiguity between divergent cell fates. This shared twofold threshold is reminiscent of autosomal syndromes of transcription-factor haploinsufficiency, including XY sex reversal associated with mutations in SOX9. Our results demonstrate that nucleocytoplasmic shuttling of SRY is necessary for robust initiation of testicular development. Although also characteristic of ungulate orthologs, such shuttling is not conserved among rodents wherein impaired nuclear export of the high-mobility group box and import-dependent phosphorylation are compensated by a microsatellite-associated transcriptional activation domain. Human sex reversal due to subtle defects in the nucleocytoplasmic shuttling of SRY suggests that its transcriptional activity lies near the edge of developmental ambiguity.

Microsatellite-encoded domain in rodent Sry functions as a genetic capacitor to enable the rapid evolution of biological novelty

The male program of therian mammals is determined by Sry, a transcription factor encoded by the Y chromosome. Specific DNA binding is mediated by a high mobility group (HMG) box. Expression of Sry in the gonadal ridge activates a Sox9-dependent gene regulatory network leading to testis formation. A subset of Sry alleles in superfamily Muroidea (order Rodentia) is remarkable for insertion of an unstable DNA microsatellite, most commonly encoding (as in mice) a CAG repeat-associated glutamine-rich domain. We provide evidence, based on an embryonic pre-Sertoli cell line, that this domain functions at a threshold length as a genetic capacitor to facilitate accumulation of variation elsewhere in the protein, including the HMG box. The glutamine-rich domain compensates for otherwise deleterious substitutions in the box and absence of nonbox phosphorylation sites to ensure occupancy of DNA target sites. Such compensation enables activation of a male transcriptional program despite perturbations to the box. Whereas human SRY requires nucleocytoplasmic shuttling and coupled phosphorylation, mouse Sry contains a defective nuclear export signal analogous to a variant human SRY associated with inherited sex reversal. We propose that the rodent glutamine-rich domain has (i) fostered accumulation of cryptic intragenic variation and (ii) enabled unmasking of such variation due to DNA replicative slippage. This model highlights genomic contingency as a source of protein novelty at the edge of developmental ambiguity and may underlie emergence of non-Sry-dependent sex determination in the radiation of Muroidea.

Disorders of sex development: new genes, new concepts

Formerly known as 'intersex' conditions, disorders of sex development (DSDs) are congenital conditions in which chromosomal, gonadal or anatomical sex is atypical. A complete revision of the nomenclature and classification of DSDs has been undertaken, which emphasizes the genetic aetiology of these disorders and discards pejorative terms. Uptake of the new terminology is widespread. DSDs affecting gonadal development are perhaps the least well understood. Unravelling the molecular mechanisms underlying gonadal development has revealed new causes of DSDs, although a specific molecular diagnosis is made in only ∼20% of patients. Conversely, identification of the molecular causes of DSDs has provided insight into the mechanisms of gonadal development. Studies of N-ethyl-N-nitrosourea mutagenesis in the mouse, and multigene diagnostic screening and genome-wide approaches, such as array-comparative genomic hybridization and next-generation sequencing, in patients with DSDs are accelerating the discovery of genes involved in gonadal development and DSDs. Furthermore, long-range gene regulatory mutations and multiple gene mutations are emerging as new causes of DSDs. Patients with DSDs, their parents and medical staff are confronted with challenging decisions regarding gender assignment, genital surgery and lifelong care. These advances are refining prognostic prediction and systematically improving the diagnosis and long-term management of children with DSDs.

Gender Development in 46,XY DSD: Influences of Chromosomes, Hormones, and Interactions with Parents and Healthcare Professionals

Variables that impact gender development in humans are difficult to evaluate. This difficulty exists because it is not usually possible to tease apart biological influences on gender from social variables. People with disorders of sex development, or DSD, provide important opportunities to study gender within individuals for whom biologic components of sex can be discordant with social components of gender. While most studies of gender development in people with 46,XY DSD have historically emphasized the importance of genes and hormones on gender identity and gender role, more recent evidence for a significant role for socialization exists and is considered here. For example, the influence of parents' perceptions of, and reactions to, DSD are considered. Additionally, the impact of treatments for DSD such as receiving gonadal surgeries or genitoplasty to reduce genital ambiguity on the psychological development of people with 46,XY DSD is presented. Finally, the role of multi-disciplinary care including access to peer support for advancing medical, surgical and psychosexual outcomes of children and adults with 46,XY DSD, regardless of sex of rearing, is discussed.

Curcuminoid binding to embryonal carcinoma cells: reductive metabolism, induction of apoptosis, senescence, and inhibition of cell proliferation

Curcumin preparations typically contain a mixture of polyphenols, collectively referred to as curcuminoids. In addition to the primary component curcumin, they also contain smaller amounts of the co-extracted derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids can be differentially solubilized in serum, which allows for the systematic analysis of concentration-dependent cellular binding, biological effects, and metabolism. Technical grade curcumin was solubilized in fetal calf serum by two alternative methods yielding saturated preparations containing either predominantly curcumin (60%) or bisdemethoxycurcumin (55%). Continual exposure of NT2/D1 cells for 4–6 days to either preparation in cell culture media reduced cell division (1–5 µM), induced senescence (6–7 µM) or comprehensive cell death (8–10 µM) in a concentration-dependent manner. Some of these effects could also be elicited in cells transiently exposed to higher concentrations of curcuminoids (47 µM) for 0.5–4 h. Curcuminoids induced apoptosis by generalized activation of caspases but without nucleosomal fragmentation. The equilibrium binding of serum-solubilized curcuminoids to NT2/D1 cells incubated with increasing amounts of curcuminoid-saturated serum occurred with apparent overall dissociation constants in the 6–10 µM range. However, the presence of excess free serum decreased cellular binding in a hyperbolic manner. Cellular binding was overwhelmingly associated with membrane fractions and bound curcuminoids were metabolized in NT2/D1 cells via a previously unidentified reduction pathway. Both the binding affinities for curcuminoids and their reductive metabolic pathways varied in other cell lines. These results suggest that curcuminoids interact with cellular binding sites, thereby activating signal transduction pathways that initiate a variety of biological responses. The dose-dependent effects of these responses further imply that distinct cellular pathways are sequentially activated and that this activation is dependent on the affinity of curcuminoids for the respective binding sites. Defined serum-solubilized curcuminoids used in cell culture media are thus suitable for further investigating the differential activation of signal transduction pathways.

The human testis-determining factor SRY localizes in midbrain dopamine neurons and regulates multiple components of catecholamine synthesis and metabolism

The male gender is determined by the sex-determining region on the Y chromosome (SRY) transcription factor. The unexpected action of SRY in the control of voluntary movement in male rodents suggests a role in the regulation of dopamine transmission and dopamine-related disorders with gender bias, such as Parkinson's disease. We investigated SRY expression in the human brain and function in vitro. SRY immunoreactivity was detected in the human male, but not female substantia nigra pars compacta, within a sub-population of tyrosine hydroxylase (TH) positive neurons. SRY protein also co-localized with TH positive neurons in the ventral tegmental area, and with GAD-positive neurons in the substantia nigra pars reticulata. Retinoic acid-induced differentiation of human precursor NT2 cells into dopaminergic cells increased expression of TH, NURR1, D2 R and SRY. In the human neuroblastoma cell line, M17, SRY knockdown resulted in a reduction in TH, DDC, DBH and MAO-A expression; enzymes which control dopamine synthesis and metabolism. Conversely, SRY over-expression increased TH, DDC, DBH, D2 R and MAO-A levels, accompanied by increased extracellular dopamine levels. A luciferase assay demonstrated that SRY activated a 4.6 kb 5' upstream regulatory region of the human TH promoter/nigral enhancer. Combined, these results suggest that SRY plays a role as a positive regulator of catecholamine synthesis and metabolism in the human male midbrain. This ancillary genetic mechanism might contribute to gender bias in fight-flight behaviours in men or their increased susceptibility to dopamine disorders, such as Parkinson's disease and schizophrenia.

Expression features of SOX9 associate with tumor progression and poor prognosis of hepatocellular carcinoma

BACKGROUND

SOX9 as a member of the SOX (SRY [sex determining region Y] box) gene superfamily has been previously demonstrated to be a proto-oncogene in a variety of malignancies. However, the clinical significance of SOX9 expression in hepatocellular carcinoma (HCC) remains unclear. The aim of this study was to investigate the expression of SOX9 in HCC and determine its correlation with tumor progression and prognosis.

METHODS

One-hundred and thirty HCC patients who had undergone curative liver resection were selected and immunohistochemistry, Western blotting, and quantitative real time polymerase chain reaction (Q-PCR) were performed to analyze SOX9 expression in the respective tumors.

RESULTS

Immunohistochemistry, Western blotting, and Q-PCR consistently confirmed SOX9 overexpression in HCC tissues compared with their adjacent nonneoplastic tissues (P ≪ 0.01). Additionally, immunostaining showed more SOX9 positive cells in the higher tumor stage (T3 ~ 4) and tumor grade (G3) than in the lower tumor stage (T1 ~ 2, P = 0.03) and tumor grade (G1 ~ 2, P = 0.01), respectively. Moreover, HCC patients with high SOX9 expression were significantly associated with lower 5-year overall survival (P ≪ 0.01) and lower 5-year disease-free survival (P ≪ 0.01), respectively. The Cox proportional hazards model further showed that SOX9 over-expression was an independent poor prognostic factor for both 5-year disease-free survival (hazards ratio [HR] = 2.621, 95% confidence interval[CI] = 1.548-5.829, P = 0.01) and 5-year overall survival (HR = 3.825, CI = 1.638-7.612, P = 0.003) in HCC.

CONCLUSION

Our data suggest for the first time that the overexpression of SOX9 protein in HCC tissues is of predictive value on tumor progression and poor prognosis.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/9029740396926377.

Excess DAX1 leads to XY ovotesticular disorder of sex development (DSD) in mice by inhibiting steroidogenic factor-1 (SF1) activation of the testis enhancer of SRY-box-9 (Sox9)

Human DAX1 duplications cause dosage-sensitive sex reversal (DSS) whereby chromosomally XY individuals can develop as females due to gonadal dysgenesis. However, the mechanism of DSS-adrenal hypoplasia congenita on X, gene 1 (DAX1) action in the fetal testis is unknown. We show that in fetal testes from XY Dax1-overexpressing transgenic mice, the expression of the key testis-promoting gene sex-determining region on Y (SRY)-box-9 (Sox9) is reduced. Moreover, in XY Sox9 heterozygotes, in which testis development is usually normal, Dax1 overexpression results in ovotestes, suggesting a DAX1-SOX9 antagonism. The ovarian portion of the XY ovotestes was characterized by expression of the granulosa cell marker, Forkhead box-L2, with complete loss of the Sertoli cell markers, SOX9 and anti-Müllerian hormone, and the Leydig cell marker CYP17A1. However, the expression of SRY and steroidogenic factor-1 (SF1), two key transcriptional regulators of Sox9, was retained in the ovarian portion of the XY ovotestes. Using reporter mice, Dax1 overexpression reduced activation of TES, the testis enhancer of Sox9, indicating that DAX1 might repress Sox9 expression via TES. In cultured cells, increasing levels of DAX1 antagonized SF1-, SF1/SRY-, and SF1/SOX9-mediated activation of TES, due to reduced binding of SF1 to TES, providing a likely mechanism for DSS.

The molecular and cellular basis of gonadal sex reversal in mice and humans

The mammalian gonad is adapted for the production of germ cells and is an endocrine gland that controls sexual maturation and fertility. Gonadal sex reversal, namely, the development of ovaries in an XY individual or testes in an XX, has fascinated biologists for decades. The phenomenon suggests the existence of genetic suppressors of the male and female developmental pathways and molecular genetic studies, particularly in the mouse, have revealed controlled antagonism at the core of mammalian sex determination. Both testis and ovary determination represent design solutions to a number of problems: how to generate cells with the right properties to populate the organ primordium; how to produce distinct organs from an initially bipotential primordium; how to pattern an organ when the expression of key cell fate determinants is initiated only in a discrete region of the primordium and extends to other regions asynchronously; how to coordinate the interaction between distinct cell types in time and space and stabilize the resulting morphology; and how to maintain the differentiated state of the organ throughout the adult period. Some of these, and related problems, are common to organogenesis in general; some are distinctive to gonad development. In this review, we discuss recent studies of the molecular and cellular events underlying testis and ovary development, with an emphasis on the phenomenon of gonadal sex reversal and its causes in mice and humans. Finally, we discuss sex-determining loci and disorders of sex development in humans and the future of research in this important area. WIREs Dev Biol 2012, 1:559–577. doi: 10.1002/wdev.42

Wnt signaling in ovarian development inhibits Sf1 activation of Sox9 via the Tesco enhancer

Genome analysis of patients with disorders of sex development, and gain- and loss-of-function studies in mice indicate that gonadal development is regulated by opposing signals. In females, the Wnt/β-catenin canonical pathway blocks testicular differentiation by repressing the expression of the Sertoli cell-specific gene Sox9 by an unknown mechanism. Using cell and embryonic gonad culture models, we show that activation of the Wnt/β-catenin pathway inhibits the expression of Sox9 and Amh, whereas mRNA and protein levels of Sry and steroidogenic factor 1 (Sf1), two key transcriptional regulators of Sox9, are not altered. Ectopic activation of Wnt/β-catenin signaling in male gonads led to a loss of Sf1 binding to the Tesco enhancer and absent Sox9 expression that we also observed in wild-type ovaries. Moreover, ectopic Wnt/β-catenin signaling induced the expression of the female somatic cell markers, Bmp2 and Rspo1, as a likely consequence of Sox9 loss. Wnt/β-catenin signaling in XY gonads did not, however, affect gene expression of the steroidogenic Leydig cell Sf1 target gene, Cyp11a1, or Sf1 binding to the Cyp11a1 promoter. Our data support a model in ovary development whereby activation of β-catenin prevents Sf1 binding to the Sox9 enhancer, thereby inhibiting Sox9 expression and Sertoli cell differentiation.

Male sex determination: insights into molecular mechanisms

Disorders of sex development often arise from anomalies in the molecular or cellular networks that guide the differentiation of the embryonic gonad into either a testis or an ovary, two functionally distinct organs. The activation of the Y-linked gene Sry (sex-determining region Y) and its downstream target Sox9 (Sry box-containing gene 9) triggers testis differentiation by stimulating the differentiation of Sertoli cells, which then direct testis morphogenesis. Once engaged, a genetic pathway promotes the testis development while actively suppressing genes involved in ovarian development. This review focuses on the events of testis determination and the struggle to maintain male fate in the face of antagonistic pressure from the underlying female programme.