Male sex determination: insights into molecular mechanisms

Epigenetic control of SOX9 gene by the histone acetyltransferase P300 in human Sertoli cells

Background

The transcription factor SOX9 is a key regulator of male sexual development and Sertoli cell differentiation. Altered SOX9 expression has been implicated in the pathogenesis of disorders of sexual development (DSD) in mammals. However, limited information exists regarding the epigenetic mechanisms governing its transcriptional control during sexual development.

Methods

This study employed real-time PCR (qPCR), immunofluorescence (IIF), and chromatin immunoprecipitation (ChIP) assays to investigate the epigenetic mechanisms associated with SOX9 gene transcriptional control in human and mouse Sertoli cell lines. To identify the specific epigenetic enzymes involved in SOX9 epigenetic control, functional assays using siRNAs for P300, GCN5, and WDR5 were performed.

Results

The transcriptional activation of SOX9 was associated with selective deposition of active histone modifications, such as H3K4me3 and H3K27ac, at its enhancer and promoter regions. Importantly, the histone acetyltransferase P300 was found to be significantly enriched at the SOX9 enhancers, co-localizing with the H3K27ac and the SOX9 transcription factor. Silencing of P300 led to decreased SOX9 expression and reduced H3K27ac levels at the eSR-A and e-ALDI enhancers, demonstrating the crucial role of P300-mediated histone acetylation in SOX9 transcriptional activation. Interestingly, another histone lysine acetyltransferases like GNC5 and methyltransferases as the Trithorax/COMPASS-like may also have a relevant role in male sexual differentiation.

Conclusions

Histone acetylation by P300 at SOX9 enhancers, is a key mechanism governing the transcriptional control of this essential regulator of male sexual development. These findings provide important insights into the epigenetic basis of sexual differentiation and the potential pathogenesis of DSDs.

The study of a hermaphroditic sheep caused by a mutation in the promoter of SRY gene

In mammals, sex-determining region Y (SRY) gene plays vital role as a transcription factor to regulate the expression of the genes contributing to development of male genitals. Any mutation disrupting expression of SRY gene can cause disorders of sex development (DSDs). In this study, the examination of a hermaphroditic (female-like) Shal sheep which was referred for infertility is described. Initially, the reproductive system of the sheep was histologically and anatomically assessed. Karyotyping was used to determine the real gender of the animal. Sex hormones including progesterone, estradiol, and testosterone were measured by enzyme-linked immunosorbent assay (ELISA). Eventually, promoter part and SRY gene were sequenced and aligned to detect any potential mutation using NCBI data base. Although anatomical inspection led to identification of uterus, ovary, and enlarged clitoris as well as testes in the sheep, the karyotyping results interestingly revealed that the animal was genetically a male. Although the sheep had both male and female gonads, there were no overt signs of reproductive behavior and gamete production was not observed. Plasma steroid hormone levels were reported to be at basal levels. Additionally, a mutation was detected on the promoter of the SRY gene. In conclusion, the case implies that mutation on the promoter part of SRY gene could disrupt sexual development of the fetus culminating in DSDs in the sheep.

Chromosomal and gonadal factors regulate microglial sex effects in the aging brain

Biological sex contributes to phenotypic sex effects through genetic (sex chromosomal) and hormonal (gonadal) mechanisms. There are profound sex differences in the prevalence and progression of age-related brain diseases, including neurodegenerative diseases. Inflammation of neural tissue is one of the most consistent age-related phenotypes seen with healthy aging and disease. The pro-inflammatory environment of the aging brain has primarily been attributed to microglial reactivity and adoption of heterogeneous reactive states dependent upon intrinsic (i.e., sex) and extrinsic (i.e., age, disease state) factors. Here, we review sex effects in microglia across the lifespan, explore potential genetic and hormonal molecular mechanisms of microglial sex effects, and discuss currently available models and methods to study sex effects in the aging brain. Despite recent attention to this area, significant further research is needed to mechanistically understand the regulation of microglial sex effects across the lifespan, which may open new avenues for sex informed prevention and treatment strategies.

Identification and Expression Pattern of cyp26b1 Gene in Gonad of the Chinese Tongue Sole (Cynoglossus semilaevis)

Simple Summary

In fish, it is obvious that the asynchronous development of the gonads and sexual dimorphism limit the development of aquaculture, so the research into sex-differentiation and gonadal growth is very important. Due to the sexual reversal phenomenon (genetic females becoming phenotypic males), the Chinese tongue sole (Cynoglossus semilaevis) is a great model for investigating sex-differentiation. Herein, we report one gene involved in sex-differentiation and gonadal growth of the Chinese Tongue Sole. The gene cyp26b1 (cytochrome P450 family 26 subfamily b member 1) is a metabolizing Retinoic Acid (RA) enzyme. Since it regulates RA to control sex determination and differentiation, cyp26b1 is considered a critical part of mammals’ ovary-antagonizing and testis-determining downstream passageway of Sry (sex-determining region Y) and Sox9 (sry-box transcription factor 9). In fish, the related research is reported only on the Japanese flounder (Paralichthys olivaceus) and zebrafish (Danio rerio). In the current investigation, the identification and expression pattern of the cyp26b1 gene in the Chinese tongue sole suggested that cyp26b1 might impact sex-differentiation and gonadal development.

Abstract

As an RA-metabolizing enzyme, cyp26b1 has a substantial impact on RA-signaling pathways. The cyp26b1 gene from the Chinese tongue sole was cloned and identified in this investigation. The cyp26b1 ORF was 1536 bp in length and encoded a 512 amino acid protein. A quantitative real-time PCR (qPCR) indicated that the cyp26b1 expression is no significant sexual dimorphism in the gonads at the 80 days post-hatching (dph) stages. After 4 months post-hatching (mph), the expression of cyp26b1 showed sexual dimorphism and lower level of expression in the ovaries than in the testes. An in situ hybridization demonstrated that cyp26b1 mRNA was primarily located in the testis. Interestingly, the cyp26b1 mRNA probe was also detected in the ovaries. These results suggested that cyp26b1 participates in the sex-differentiation and gonadal development of the Chinese tongue sole.

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.

The functions of Wt1 in mouse gonad development and somatic cells differentiation

Wilms' tumour 1 (Wt1) encodes a zinc finger nuclear transcription factor which is mutated in 15-20% of Wilms' tumor, a pediatric kidney tumor. Wt1 has been found to be involved in the development of many organs. In gonads, Wt1 is expressed in genital ridge somatic cells before sex determination, and its expression is maintained in Sertoli cells and granulosa cells after sex determination. It has been demonstrated that Wt1 is required for the survival of the genital ridge cells. Homozygous mutation of Wt1 causes gonad agenesis. Recent studies find that Wt1 plays important roles in lineage specification and maintenance of gonad somatic cells. In this review, we will summarize the recent research works about Wt1 in gonadal somatic cell differentiation.

Tenuous transcriptional threshold of human sex determination. II. SRY exploits water-mediated clamp at the edge of ambiguity

Y-encoded transcription factor SRY initiates male differentiation in therian mammals. This factor contains a high-mobility-group (HMG) box, which mediates sequence-specific DNA binding with sharp DNA bending. A companion article in this issue described sex-reversal mutations at box position 72 (residue 127 in human SRY), invariant as Tyr among mammalian orthologs. Although not contacting DNA, the aromatic ring seals the domain's minor wing at a solvent-exposed junction with a basic tail. A seeming paradox was posed by the native-like biochemical properties of inherited Swyer variant Y72F: its near-native gene-regulatory activity is consistent with the father's male development, but at odds with the daughter's XY female somatic phenotype. Surprisingly, aromatic rings (Y72, F72 or W72) confer higher transcriptional activity than do basic or polar side chains generally observed at solvated DNA interfaces (Arg, Lys, His or Gln). Whereas biophysical studies (time-resolved fluorescence resonance energy transfer and heteronuclear NMR spectroscopy) uncovered only subtle perturbations, dissociation of the Y72F complex was markedly accelerated relative to wild-type. Studies of protein-DNA solvation by molecular-dynamics (MD) simulations of an homologous high-resolution crystal structure (SOX18) suggest that Y72 para-OH anchors a network of water molecules at the tail-DNA interface, perturbed in the variant in association with nonlocal conformational fluctuations. Loss of the Y72 anchor among SRY variants presumably "unclamps" its basic tail, leading to (a) rapid DNA dissociation despite native affinity and (b) attenuated transcriptional activity at the edge of sexual ambiguity. Conservation of Y72 suggests that this water-mediated clamp operates generally among SRY and metazoan SOX domains.

Sex Determination and Differentiation in Teleost: Roles of Genetics, Environment, and Brain

The fish reproductive system is a complex biological system. Nonetheless, reproductive organ development is conserved, which starts with sex determination and then sex differentiation. The sex of a teleost is determined and differentiated from bipotential primordium by genetics, environmental factors, or both. These two processes are species-specific. There are several prominent genes and environmental factors involved during sex determination and differentiation. At the cellular level, most of the sex-determining genes suppress the female pathway. For environmental factors, there are temperature, density, hypoxia, pH, and social interaction. Once the sexual fate is determined, sex differentiation takes over the gonadal developmental process. Environmental factors involve activation and suppression of various male and female pathways depending on the sexual fate. Alongside these factors, the role of the brain during sex determination and differentiation remains elusive. Nonetheless, GnRH III knockout has promoted a male sex-biased population, which shows brain involvement during sex determination. During sex differentiation, LH and FSH might not affect the gonadal differentiation, but are required for regulating sex differentiation. This review discusses the role of prominent genes, environmental factors, and the brain in sex determination and differentiation across a few teleost species.

S. Sex Determination and Sex Differentiation

Sex determination is arguably the most defining moment of our lives, the point where we inherit X or Y chromosome from our father. This initiates a cascade of events that sets in a train of morphological changes, genetic regulations and molecular mechanisms. Following this, our fate is further sealed during sex differentiation and gonadal development owing to the action of sex-specific gonadal hormones. Therefore, the profoundly divergent journeys of male and female lives are decided just by the toss of a genetic coin. The existence of a third gender is also an undeniable aspect of our society. The understanding of the functioning and genetic regulation of the complex process of sexual determination and differentiation is pivotal in comprehension of the basis of human life. Any deviation from the usual mechanisms in the critical stages of development leads to disorders of sexual differentiation leading to sexual ambiguity among individuals. This review discusses the mechanisms that contribute to female and male sex determination and gonadal development, in an attempt to understand the basics of human sex.

Transverse testicular ectopia associated with persistent Mullerian duct syndrome in infertile male: two case reports and literature review

Transverse testicular ectopia (TTE) associated with persistent Mullerian duct syndrome (PMDS) is a rare form of male pseudohermaphroditism usually unexpectedly found at surgery for cryptorchidism or inguinal hernia in children. Its etiology and prevalence are unclear, although defects in the gene that encodes anti-Mullerian hormone (AMH) or AMH receptor has been generally considered as the major cause. Adult cases of TTE associated with PMDS are even more peculiar, as the adult patients usually present more complex medical history, require more comprehensive medical examination and management. Two adult men with normal karyotype were referred to the urology outpatient clinic for infertility and cryptorchidism. Semen analysis showed both patients were azoospermic. Ultrasound and computed tomography (CT) found both testes were located at the same side of abdominal cavity or pelvic cavity, which was confirmed during the laparoscopic exploration. A tubular structure adhering to the spermatic cord was also found in both cases. Laparoscopic-assisted transabdominal orchiopexy was performed and the tubular mass was removed. Pathological examination confirmed the existence of Mullerian duct, which showed positive immunostaining of the uterus marker genes. The principles of treatment include the restoration of testes, the preservation of fertility, and the prevention of malignancy. Much attention should be payed to avoid damage of fertile testes and vas deferens in the surgery. Long-term postoperative follow-up is necessary for assessment of malignant transformation and infertility.

Clinical implications of Y chromosome microdeletions among infertile men

Male factor infertility contributes significantly to couples facing difficulty achieving a pregnancy. Genetic factors, and specifically those related to the Y chromosome, may occur in up to 15% of men with oligozoospermia or azoospermia. A subset of loci within the Y chromosome, known as the azoospermia factors (AZFa, AZFb, and AZFc), have been associated with male infertility. Emerging evidence has demonstrated that microdeletions of at least a subset of these regions may also have impacts on systemic conditions. This review provides a brief review of male infertility and the structure of the Y chromosome, and further highlights the role of Y chromosome microdeletions in male infertility and other systemic disease.

Sex determination, gonadal sex differentiation, and plasticity in vertebrate species

A diverse array of sex determination (SD) mechanisms, encompassing environmental to genetic, have been found to exist among vertebrates, covering a spectrum from fixed SD mechanisms (mammals) to functional sex change in fishes (sequential hermaphroditic fishes). A major landmark in vertebrate SD was the discovery of the SRY gene in 1990. Since that time, many attempts to clone an SRY ortholog from nonmammalian vertebrates remained unsuccessful, until 2002, when DMY/dmrt1by was discovered as the SD gene of a small fish, medaka. Surprisingly, however, DMY/dmrt1by was found in only 2 species among more than 20 species of medaka, suggesting a large diversity of SD genes among vertebrates. Considerable progress has been made over the last 3 decades, such that it is now possible to formulate reasonable paradigms of how SD and gonadal sex differentiation may work in some model vertebrate species. This review outlines our current understanding of vertebrate SD and gonadal sex differentiation, with a focus on the molecular and cellular mechanisms involved. An impressive number of genes and factors have been discovered that play important roles in testicular and ovarian differentiation. An antagonism between the male and female pathway genes exists in gonads during both sex differentiation and, surprisingly, even as adults, suggesting that, in addition to sex-changing fishes, gonochoristic vertebrates including mice maintain some degree of gonadal sexual plasticity into adulthood. Importantly, a review of various SD mechanisms among vertebrates suggests that this is the ideal biological event that can make us understand the evolutionary conundrums underlying speciation and species diversity.

Molecular analysis for sex determination in forensic dentistry: a systematic review

Background

Sex determination can be useful in forensic casework, such as in mass disasters, transportation accidents, and cases of a missing person or sexual assault. The remnants of the body can be traced by DNA of the victim, using samples from various sources such as teeth, oral epithelial tissue, and saliva.

Main body

The review aimed to describe research in forensic dentistry with DNA source from the oral region and methods of the applied DNA analysis. A search in PubMed, Google Scholar, and Scopus electronic databases from 2009 to 2019 was conducted to include studies according to PRISMA guidelines. Ten studies were eligible for the review. Genetic markers originated from dentin, dental pulp, saliva, or epithelial cells from buccal tissue and prosthesis. The applied DNA analysis methods were PCR, real-time PCR, and nested PCR.

Conclusions

The published articles mostly showed successful DNA extraction and sex determination, but the rate of success declined as the sample source underwent manipulation to mimic the forensic conditions. Amelogenin, SRY, and DYS14 were reliable indicators for sex determination. Molecular analysis has proved to be efficient and accurate, but the daily forensic practice must select the most appropriate method according to the available body remnants.

Alterations of sex determination pathways in the genital ridges of males with limited Y chromosome genes†

We previously demonstrated that in the mouse only two Y chromosome genes are required for a male to produce an offspring with the help of assisted reproduction technologies (ART): testis determinant Sry and spermatogonial proliferation factor Eif2s3y. Subsequently, we have shown that the function of these genes can be replaced by transgenic overexpression of their homologs, autosomally encoded Sox9 and X-chromosome encoded Eif2s3x. Males with Y chromosome contribution limited to two (XEif2s3yOSry), one (XEif2s3yOSox9 and XOSry,Eif2s3x), and no genes (XOSox9,Eif2s3x) produced haploid germ cells and sired offspring after ART. However, despite successful assisted reproductive outcome, they had smaller testes and displayed abnormal development of the seminiferous epithelium and testicular interstitium. Here we explored whether these testicular defects originated from altered pro-testis and pro-ovary factor signaling in genital ridges at the time of sex determination. Timed pregnancies were generated to obtain transgenic XEif2s3yOSry, XEif2s3yOSox9, XOSry,Eif2s3x, XOSox9,Eif2s3x, and wild-type XX and XY fetuses at 12.5 days post coitum. Dissected genital ridges were assessed for their morphology and anatomy, and expression of pro-testis and pro-ovary transcripts. All transgenic males displayed incomplete masculinization of gonadal shape, impaired development of testicular cords and gonadal vasculature, and decreased expression of factors promoting male pathway. Fetal gonad masculinization was more effective when sex determination was driven by the Sry transgene, in the presence of Y chromosome genes, and to a lesser extent a double dosage of X genes. The study adds to the understanding of the role of Y chromosome genes and their homologs during sex determination.

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.

Disorders of sex development: Genetic characterization of a patient cohort

Disorders of sex development (DSDs) are congenital conditions in which the external appearance of the individual does not coincide with the chromosomal constitution or the gonadal sex. In other words, there is an ambiguous or intermediate condition between the male and female phenotypes of the anatomical sex. These atypical conditions are manifested in several ways, ranging from genital ambiguity to phenotypes that are so attenuated that they can go unnoticed or appear normal. Currently, there is a lack of understanding of the factors responsible for these outcomes; however, they are likely to be conditioned by genetic, hormonal and environmental factors during prenatal and postnatal development. The present study determined the genetic etiology of DSDs in Colombian patients by conventional cytogenetic analysis, FISH and MLPA (for SF1, DAX1, SOX9, SRY and WNT4). A cohort of 43 patients with clinical phenotypes of sex development disorder was used in the present study. Using this multistep experimental approach, a diagnostic percentage of 25.58% was obtained: 17 patients (39.53%) were classified as having gonadal development disorders, the majority of which were ovotesticular disorders with numerical and/or structural alterations of the sex chromosomes, 9 patients (20.93%) were classified as having testicular DSD with a 46,XY karyotype, and 3 patients (6.98%) as having ovarian DSD with a 46,XX karyotype. The remaining 14 patients (32.56%) were classified as 'other' since they could not be grouped into a specific class of gonadal development, corresponding to hypospadias and multiple congenital anomalies. These findings highlight the importance of histological and cytogenetic studies in a gonadal biopsy. In 11/43 cases, the multistep experimental protocol presented in the present study yielded etiological or histological findings that could be used to define the medical management of patients with DSDs. In conclusion, for the etiological diagnosis of DSDs, a broad‑spectrum approach that includes endocrinological tests, conventional karyotyping, molecular karyotyping by FISH and, molecular tests is required, in addition to gonadal tissue analyses, to identify genetic alterations.

Pluripotent Cell Models for Gonadal Research

Sex development is a complex process involving many genes and hormones. Defects in this process lead to Differences of Sex Development (DSD), a group of heterogeneous conditions not as rare as previously thought. Part of the obstacles in proper management of these patients is due to an incomplete understanding of the genetics programs and molecular pathways involved in sex development and DSD. Several challenges delay progress and the lack of a proper model system for the single patient severely hinders advances in understanding these diseases. The revolutionary techniques of cellular reprogramming and guided in vitro differentiation allow us now to exploit the versatility of induced pluripotent stem cells to create alternatives models for DSD, ideally on a patient-specific personalized basis.

Lactational exposure to environmentally relevant benzo(a)pyrene causes astrocytic activation and anxiety-like behavior in male mice

Previous studies have shown the adversely neurodevelopmental effects of exposure to benzo(a)pyrene (BaP) at early life stage. However, it is unclear the effects of lactational exposure to environmentally relevant BaP on anxiety-like behavior and the molecular mechanisms related. In this study, lactational exposure to 1 and 10 μg/kg bw BaP from postnatal day 3-21 caused anxiety-like behavior and alterations of the expressions of the neurodevelopment and anxiety-related genes in adolescence male mice using O cycle maze. Moreover, BaP exposure increased the expression level of glial fibrillary acidic protein, a typical marker of astrocytes, in hippocampus of male offspring. The release of pro-inflammatory cytokines interleukin 6 and tumor necrosis factor α was also elevated in BaP-treated offspring. Further, lactational exposure to BaP decreased the level of glutathione and the expressions of antioxidant genes (Thioredoxin 1 and Glutaredoxin 2) in male offspring. Our study demonstrated that environmentally relevant BaP lactational exposure caused anxiety-like behavior in male offspring involved in astrocytic activation, neuroinflammation, and antioxidant capability dysfunction.

Gene dosage of DAX-1, determining in sexual differentiation: duplication of DAX-1 in two sisters with gonadal dysgenesis

Two sisters phenotypically normal females, presenting with tumor abdominal mass with histopathological findings of teratoma and gonadoblastoma associated to 46,XY male-to-female sex reversal syndrome, secondary to a duplication in DAX-1, possibly inherited of maternal gonadal mosaicism. Copy number variation and functional effects of the duplication were done by MLPA multiplex ligation-dependent probe amplification and real time PCR. DAX-1, also known as dosage sensitive sex reversal gene (DSS), is considered the most likely candidate gene involved in XY gonadal dysgenesis when overexpressed. The excess of DAX-1 gene disturbs testicular development by down regulation of SF-1, WT1, and SOX9. This is the first report of 46,XY sex reversal in two siblings who have a maternally inherited duplication of DAX-1 associated with reduced levels of expression of downstream genes as SOX9-SF1.

A Human Gonadal Cell Model From Induced Pluripotent Stem Cells

Sertoli cells are main players in the male gonads development and their study may shed light on 46,XY disorders of sex development (DSD). Mature primary Sertoli cells are incapable of proliferating in prolonged in vitro cultures and the available Sertoli cell models have several limitations since they derive from mouse or human cancer tissues. We differentiated human fibroblasts (HFs)-derived induced pluripotent stem cells into Sertoli-like cells (SLC) and, in order to characterize this new Sertoli cell model, we performed gene expression analyses by NextGeneration Sequencing techniques. This approach revealed that our putative SLC have reduced expression of pluripotency markers and expressed Sertoli cell markers such as SRY-Related HMG-Box 9 (SOX9), vimentin (VIM), and claudin-11 (CLDN-11). More in detail, the transcriptional profile analysis suggested that these cells are in an early stage of Sertoli cells maturation. Harnessing the power of induced pluripotent stem cells, we were able to generate SLC that show genetic and functional similarities to human Sertoli cells (HSerCs). SLC could become an excellent source of patient-specific Sertoli cells that could be of paramount benefit for both basic research and personalized medicine in sex development and reproductive medicine.

Duplication of SOX9 associated with 46,XX ovotesticular disorder of sex development

RESEARCH QUESTION

The purpose of the present study was to investigate whether ten unrelated SRY-negative individuals with this sex differentiation disorder presented a double dose of SOX9 as the cause of their disease.

DESIGN

Ten unrelated SRY-negative 46,XX ovotesticular disorder of sexual development (DSD) subjects were molecularly studied. Multiplex-ligation dependent probe amplification (MLPA) and quantitative real-time PCR analysis (qRT-PCR) for SOX9 were performed.

RESULTS

The MLPA analysis demonstrated that one patient presented a heterozygous duplication of the entire SOX9 coding region (above 1.3 value of peak ratio), as well as at least a ~ 483 kb upstream duplication. Moreover, no duplication of other SOX9 probes was observed corresponding to the region between -1007 and -1500 kb upstream. A qRT-PCR analysis showed a duplication of at least -581 kb upstream and ~1.63 kb of the coding region that encompasses exon 3. The limits of the duplication were mapped approximately from ~71539762 to 72122741 of Chr17. No molecular abnormalities were found in the remaining nine patients.

CONCLUSION

This study is thought to be the first report regarding a duplication of SOX9 that is associated with the presence of 46,XX ovotesticular DSD, encompassing at least -581 kb upstream, and the almost entire coding region of the gene.

Developmental tracing of oocyte development in gonadal soma-derived factor deficiency medaka (Oryzias latipes) using a transgenic approach

Gonadal soma-derived factor (gsdf) is reported to be a male initiator in medaka based on loss- and gain- of function via targeted disruption, or transgenic over-expression. However, little is known about how gsdf promotes undifferentiated gonad entry into male pathways or prevents entry into the female pathway. We utilized a visible folliculogenesis system with a reporter cassette of dual-color fluorescence expression to identify difference between oocyte development from wildtype and gsdf deficiency medaka. A red fluorescent protein (RFP) is driven by a major component of the synaptonemal complex (SYCP3) promoter which enables RFP expression solely in oocytes after the onset of meiosis, and a histone 2b-EGFP fused protein (H2BEGFP) under the control of an elongation factor (EF1α) promoter, wildly used as a mitotic reporter of cell cycle. This mitosis-meiosis visible switch revealed that early meiotic oocytes present in gsdf deficiency were more than those in wildtype ovaries, corresponding to the decrease of inhibin expression detected by real-time qPCR analysis, suggesting gsdf is tightly involved in the process of medaka oocyte development at early stage.

Nucleotide composition and codon usage bias of SRY gene

The SRY gene is present within the sex-determining region of the Y chromosome which is responsible for maleness in mammals. The nonuniform usage of synonymous codons in the mRNA transcript for encoding a particular amino acid is the codon usage bias (CUB). Analysis of codon usage pattern is important to understand the genetic and molecular organisation of a gene. It also helps in heterologous gene expression, design of primer and synthetic gene. However, the analysis of codon usage bias of SRY gene was not yet studied. We have used bioinformatic tools to analyse codon usage bias of SRY gene across mammals. Codon bias index (CBI) indicated that the overall extent of codon usage bias was weak. The relative synonymous codon usage (RSCU) analysis suggested that most frequently used codons had an A or C at the third codon position. Compositional constraint played an important role in codon usage pattern as evident from correspondence analysis (CA). Significant correlation among nucleotides constraints indicated that both mutation pressure and natural selection affect the codon usage pattern. Neutrality plot suggested that natural selection might play a major role, while mutation pressure might play a minor role in codon usage pattern in SRY gene in different species of mammals.

Systems Toxicology of Male Reproductive Development: Profiling 774 Chemicals for Molecular Targets and Adverse Outcomes

BACKGROUND

Trends in male reproductive health have been reported for increased rates of testicular germ cell tumors, low semen quality, cryptorchidism, and hypospadias, which have been associated with prenatal environmental chemical exposure based on human and animal studies.

OBJECTIVE

In the present study we aimed to identify significant correlations between environmental chemicals, molecular targets, and adverse outcomes across a broad chemical landscape with emphasis on developmental toxicity of the male reproductive system.

METHODS

We used U.S. EPA's animal study database (ToxRefDB) and a comprehensive literature analysis to identify 774 chemicals that have been evaluated for adverse effects on male reproductive parameters, and then used U.S. EPA's in vitro high-throughput screening (HTS) database (ToxCastDB) to profile their bioactivity across approximately 800 molecular and cellular features.

RESULTS

A phenotypic hierarchy of testicular atrophy, sperm effects, tumors, and malformations, a composite resembling the human testicular dysgenesis syndrome (TDS) hypothesis, was observed in 281 chemicals. A subset of 54 chemicals with male developmental consequences had in vitro bioactivity on molecular targets that could be condensed into 156 gene annotations in a bipartite network.

CONCLUSION

Computational modeling of available in vivo and in vitro data for chemicals that produce adverse effects on male reproductive end points revealed a phenotypic hierarchy across animal studies consistent with the human TDS hypothesis. We confirmed the known role of estrogen and androgen signaling pathways in rodent TDS, and importantly, broadened the list of molecular targets to include retinoic acid signaling, vascular remodeling proteins, G-protein coupled receptors (GPCRs), and cytochrome P450s.

CITATION

Leung MC, Phuong J, Baker NC, Sipes NS, Klinefelter GR, Martin MT, McLaurin KW, Setzer RW, Darney SP, Judson RS, Knudsen TB. 2016. Systems toxicology of male reproductive development: profiling 774 chemicals for molecular targets and adverse outcomes. Environ Health Perspect 124:1050-1061; http://dx.doi.org/10.1289/ehp.1510385.

The endocrine system controlling sexual reproduction in animals: Part of the evolutionary ancient but well conserved immune system?

Drastic changes in hormone titers, in particular of steroid hormones, are intuitively interpreted as necessary and beneficial for optimal functioning of animals. Peaks in progesterone- and estradiol titers that accompany the estrus cycle in female vertebrates as well as in ecdysteroids at each molt and during metamorphosis of holometabolous insects are prominent examples. A recent analysis of insect metamorphosis yielded the view that, in general, a sharp rise in sex steroid hormone titer signals that somewhere in the body some tissue(s) is undergoing programmed cell death/apoptosis. Increased steroid production is part of this process. Typical examples are ovarian follicle cells in female vertebrates and invertebrates and the prothoracic gland cells, the main production site of ecdysteroids in larval insects. A duality emerges: programmed cell death-apoptosis is deleterious at the cellular level, but it may yield beneficial effects at the organismal level. Reconciling both opposites requires reevaluating the probable evolutionary origin and role of peptidic brain hormones that direct steroid hormone synthesis. Do e.g. Luteinizing Hormone in vertebrates and Prothoracicotropic Hormone (PTTH: acting through the Torso receptor) in insects still retain an ancient role as toxins in the early immune system? Does the functional link of some neuropeptides with Ca(2+)-induced apoptosis make sense in endocrine archeology? The endocrine system as a remnant of the ancient immune system is undoubtedly counterintuitive. Yet, we will argue that such paradigm enables the logical framing of many aspects, the endocrine one inclusive of both male and female reproductive physiology.

Sry-Independent Overexpression of Sox9 Supports Spermatogenesis and Fertility in the Mouse

The Y chromosome gene Sry is responsible for sex determination in mammals and initiates a cascade of events that direct differentiation of bipotential genital ridges toward male-specific fate. Sox9 is an autosomal gene and a primary downstream target of SRY. The activation of Sox9 in the absence of Sry is sufficient for initiation of male-specific sex determination. Sry-to-Sox9 replacement has mostly been studied in the context of sex determination during early embryogenesis. Here, we tested whether Sry-to-Sox9 replacement affects male fertility in adulthood. We examined males with the Y chromosome carrying a deletion removing the endogenous Sry, with testes determination driven either by the Sox9 (XY(Tdym1)Sox9) or the Sry (XY(Tdym1)Sry) transgenes as well as wild-type males (XY). XY(Tdym1)Sox9 males had reduced testes size, altered testes shape and vasculature, and increased incidence of defects in seminiferous epithelium underlying the coelomic blood vessel region when compared to XY(Tdym1)Sry and XY. There were no differences between XY(Tdym1)Sry and XY(Tdym1)Sox9 males in respect to sperm number, motility, morphology, and ability to fertilize oocytes in vitro, but for some parameters, transgenic males were impaired when compared to XY. In fecundity trials, XY(Tdym1)Sry, XY(Tdym1)Sox9, and XY males yielded similar average numbers of pups and litters. Overall, our findings support that males lacking the testis determinant Sry can be fertile and reinforce the notion that Sry does not play a role in mature gonads. Although transgenic Sox9 overexpression in the absence of Sry results in certain testicular abnormalities, it does not translate into fertility impairment.

Genome sequence of the Asian Tiger mosquito, Aedes albopictus, reveals insights into its biology, genetics, and evolution

The Asian tiger mosquito, Aedes albopictus, is a highly successful invasive species that transmits a number of human viral diseases, including dengue and Chikungunya fevers. This species has a large genome with significant population-based size variation. The complete genome sequence was determined for the Foshan strain, an established laboratory colony derived from wild mosquitoes from southeastern China, a region within the historical range of the origin of the species. The genome comprises 1,967 Mb, the largest mosquito genome sequenced to date, and its size results principally from an abundance of repetitive DNA classes. In addition, expansions of the numbers of members in gene families involved in insecticide-resistance mechanisms, diapause, sex determination, immunity, and olfaction also contribute to the larger size. Portions of integrated flavivirus-like genomes support a shared evolutionary history of association of these viruses with their vector. The large genome repertory may contribute to the adaptability and success of Ae. albopictus as an invasive species.

Gonadotrope-specific deletion of Dicer results in severely suppressed gonadotropins and fertility defects

Pituitary gonadotropins follicle-stimulating hormone and luteinizing hormone are heterodimeric glycoproteins expressed in gonadotropes. They act on gonads and promote their development and functions including steroidogenesis and gametogenesis. Although transcriptional regulation of gonadotropin subunits has been well studied, the post-transcriptional regulation of gonadotropin subunits is not well understood. To test if microRNAs regulate the hormone-specific gonadotropin β subunits in vivo, we deleted Dicer in gonadotropes by a Cre-lox genetic approach. We found that many of the DICER-dependent microRNAs, predicted in silico to bind gonadotropin β subunit mRNAs, were suppressed in purified gonadotropes of mutant mice. Loss of DICER-dependent microRNAs in gonadotropes resulted in profound suppression of gonadotropin-β subunit proteins and, consequently, the heterodimeric hormone secretion. In addition to suppression of basal levels, interestingly, the post-gonadectomy-induced rise in pituitary gonadotropin synthesis and secretion were both abolished in mutants, indicating a defective gonadal negative feedback control. Furthermore, mutants lacking Dicer in gonadotropes displayed severely reduced fertility and were rescued with exogenous hormones confirming that the fertility defects were secondary to suppressed gonadotropins. Our studies reveal that DICER-dependent microRNAs are essential for gonadotropin homeostasis and fertility in mice. Our studies also implicate microRNAs in gonadal feedback control of gonadotropin synthesis and secretion. Thus, DICER-dependent microRNAs confer a new layer of transcriptional and post-transcriptional regulation in gonadotropes to orchestrate the hypothalamus-pituitary-gonadal axis physiology.

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.

Prostaglandin D2 acts through the Dp2 receptor to influence male germ cell differentiation in the foetal mouse testis

Through intercellular signalling, the somatic compartment of the foetal testis is able to program primordial germ cells to undergo spermatogenesis. Fibroblast growth factor 9 and several members of the transforming growth factor β superfamily are involved in this process in the foetal testis, counteracting the induction of meiosis by retinoic acid and activating germinal mitotic arrest. Here, using in vitro and in vivo approaches, we show that prostaglandin D2 (PGD2), which is produced through both L-Pgds and H-Pgds enzymatic activities in the somatic and germ cell compartments of the foetal testis, plays a role in mitotic arrest in male germ cells by activating the expression and nuclear localization of the CDK inhibitor p21Cip1 and by repressing pluripotency markers. We show that PGD2 acts through its Dp2 receptor, at least in part through direct effects in germ cells, and contributes to the proper differentiation of male germ cells through the upregulation of the master gene Nanos2. Our data identify PGD2 signalling as an early pathway that acts in both paracrine and autocrine manners, and contributes to the differentiation of germ cells in the foetal testis.

Regulation of meiotic entry and gonadal sex differentiation in the human: normal and disrupted signaling

Meiosis is a unique type of cell division that is performed only by germ cells to form haploid gametes. The switch from mitosis to meiosis exhibits a distinct sex-specific difference in timing, with female germ cells entering meiosis during fetal development and male germ cells at puberty when spermatogenesis is initiated. During early fetal development, bipotential primordial germ cells migrate to the forming gonad where they remain sexually indifferent until the sex-specific differentiation of germ cells is initiated by cues from the somatic cells. This irreversible step in gonadal sex differentiation involves the initiation of meiosis in fetal ovaries and prevention of meiosis in the germ cells of fetal testes. During the last decade, major advances in the understanding of meiosis regulation have been accomplished, with the discovery of retinoic acid as an inducer of meiosis being the most prominent finding. Knowledge about the molecular mechanisms regulating meiosis signaling has mainly been established by studies in rodents, while this has not yet been extensively investigated in humans. In this review, the current knowledge about the regulation of meiosis signaling is summarized and placed in the context of fetal gonad development and germ cell differentiation, with emphasis on results obtained in humans. Furthermore, the consequences of dysregulated meiosis signaling in humans are briefly discussed in the context of selected pathologies, including testicular germ cell cancer and some forms of male infertility.

DMRT1 protects male gonadal cells from retinoid-dependent sexual transdifferentiation

Mammalian sex determination initiates in the fetal gonad with specification of bipotential precursor cells into male Sertoli cells or female granulosa cells. This choice was long presumed to be irreversible, but genetic analysis in the mouse recently revealed that sexual fates must be maintained throughout life. Somatic cells in the testis or ovary, even in adults, can be induced to transdifferentiate to their opposite-sex equivalents by loss of a single transcription factor, DMRT1 in the testis or FOXL2 in the ovary. Here, we investigate what mechanism DMRT1 prevents from triggering transdifferentiation. We find that DMRT1 blocks testicular retinoic acid (RA) signaling from activating genes normally involved in female sex determination and ovarian development and show that inappropriate activation of these genes can drive sexual transdifferentiation. By preventing activation of potential feminizing genes, DMRT1 allows Sertoli cells to participate in RA signaling, which is essential for reproduction, without being sexually reprogrammed.

Pleiotropic Activities of HGF/c-Met System in Testicular Physiology: Paracrine and Endocrine Implications

In the last decades, a growing body of evidence has been reported concerning the expression and functional role of hepatocyte growth factor (HGF) on different aspects of testicular physiology. This review has the aim to summarize what is currently known regarding this topic. From early embryonic development to adult age, HGF and its receptor c-Met appeared to be clearly detectable in the testis. These molecules acquire different distribution patterns and roles depending on the developmental stage or the post-natal age considered. HGF acts as a paracrine modulator of testicular functions promoting the epithelium-mesenchyme cross-talk as described even in other organs. Interestingly, it has been reported that testicular HGF acts even as an autocrine factor and that its receptor might be modulated by endocrine signals that change at puberty: HGF receptor expressed by Sertoli cells, in fact, is up-regulated by FSH administration. HGF is in turn able to modify endocrine state of the organism being able to increase testosterone secretion of both fetal and adult Leydig cells. Moreover, c-Met is expressed in mitotic and meiotic male germ cells as well as in spermatozoa. The distribution pattern of c-Met on sperm cell membrane changes in the caput and cauda epididymal sperms and HGF is able to maintain epididymal sperm motility in vitro suggesting a physiological role of this growth factor in the acquisition of sperm motility. Noteworthy changes in HGF concentration in seminal plasma have been reported in different andrological diseases. All together these data indicate that HGF has a role in the control of spermatogenesis and sperm quality either directly, acting on male germ cells, or indirectly acting on tubular and interstitial somatic cells of the testis.

The chemosensitivity of testicular germ cell tumors

Although rare cancers overall, testicular germ cell tumors (TGCTs) are the most common type of cancer in young males below 40 years of age. Both subtypes of TGCTs, i.e., seminomas and non-seminomas, are highly curable and the majority of even metastatic patients may expect to be cured. These high cure rates are not due to the indolent nature of these cancers, but rather to their sensitivity to chemotherapy (and for seminomas to radiotherapy). The delineation of the cause of chemosensitivity at the molecular level is of paramount importance, because it may provide insights into the minority of TGCTs that are chemo-resistant and, thereby, provide opportunities for specific therapeutic interventions aimed at reverting them to chemosensitivity. In addition, delineation of the molecular basis of TGCT chemo-sensitivity may be informative for the cause of chemo-resistance of other more common types of cancer and, thus, may create new therapeutic leads. p53, a frequently mutated tumor suppressor in cancers in general, is not mutated in TGCTs, a fact that has implications for their chemo-sensitivity. Oct4, an embryonic transcription factor, is uniformly expressed in the seminoma and embryonic carcinoma components of non-seminomas, and its interplay with p53 may be important in the chemotherapy response of these tumors. This interplay, together with other features of TGCTs such as the gain of genetic material from the short arm of chromosome 12 and the association with disorders of testicular development, will be discussed in this paper and integrated in a unifying hypothesis that may explain their chemo-sensitivity.

MEF2 is restricted to the male gonad and regulates expression of the orphan nuclear receptor NR4A1

Leydig cell steroidogenesis is controlled by the pituitary gonadotropin LH that activates several signaling pathways, including the Ca(2+)/calmodulin kinase I (CAMKI) pathway. In other tissues, CAMKI regulates the activity of the myocyte enhancer factor 2 (MEF2) transcription factors. MEF2 factors are essential regulators of cell differentiation and organogenesis in numerous tissues but their expression and role in the mammalian gonad had not been explored. Here we show that MEF2 factors are expressed in a sexually dimorphic pattern in the mouse gonad. MEF2 factors are present in the testis throughout development and into adulthood but absent from the ovary. In the testis, MEF2 was localized mainly in the nucleus of both somatic lineages, the supporting Sertoli cells and the steroidogenic Leydig cells. In Leydig cells, MEF2 was found to activate the expression of Nr4a1, a nuclear receptor important for hormone-induced steroidogenesis. In these cells MEF2 also cooperates with forskolin and CAMKI to enhance Nr4a1 promoter activity via two MEF2 elements (-318 and -284 bp). EMSA confirmed direct binding of MEF2 to these elements whereas chromatin immunoprecipitation revealed that MEF2 recruitment to the proximal Nr4a1 promoter was increased following hormonal stimulation. Modulation of endogenous MEF2 protein level (small interfering RNA-mediated knockdown) or MEF2 activity (MEF2-Engrailed active dominant negative) led to a significant decrease in Nr4a1 mRNA levels in Leydig cells. All together, our results identify MEF2 as a novel testis-specific transcription factor, supporting a role for this factor in male sex differentiation and function. MEF2 was also positioned upstream of NR4A1 in a regulatory cascade controlling Leydig cell gene expression.

Elucidation of distinctive genomic DNA structures in patients with 46,XX testicular disorders of sex development using genome wide analyses

PURPOSE

Although several genes, including the SRY gene, are involved in testicular differentiation, the entire mechanism of this differentiation remains unclear. We performed genome wide analysis in patients with 46,XX testicular disorders of sex development to comprehensively elucidate the mechanisms of testicular differentiation.

MATERIALS AND METHODS

Whole genomic DNA was extracted from the peripheral blood of 4 patients with 46,XX testicular disorders of sex development who were SRY negative. Genomic DNA was hybridized to a GeneChip® human mapping 250K array set. Compared to normal female data, we detected common loss of heterozygosity and copy number variation regions in 4 patients using Genotyping Console™ software.

RESULTS

Loss of heterozygosity was detected in 19 regions of 11 chromosomes. A total of 27 genes or nearby genomic areas were included in the applicable regions. Copy number loss was recognized in 13 regions of 10 chromosomes, and these regions included 55 genes. Copy number gain was detected in 6 regions of 4 chromosomes, which included the upstream region of the SOX3 gene.

CONCLUSIONS

The regions with loss of heterozygosity did not contain genes associated with testicular differentiation. However, the upstream area of the SOX3 gene, which is located in Xq27.1, was included in the region of copy number gain. These results suggest that high expression of the SOX3 gene led to testicular differentiation despite SRY gene loss. As this applicable area is not within a coding region, genome wide analyses were valuable for detecting the novel regions associated with testicular differentiation.

CYP26B1 promotes male germ cell differentiation by suppressing STRA8-dependent meiotic and STRA8-independent mitotic pathways

Germ cell sex is defined by factors derived from somatic cells. CYP26B1 is known to be a male sex-promoting factor that inactivates retinoic acid (RA) in somatic cells. In CYP26B1-null XY gonads, germ cells are exposed to a higher level of RA than in normal XY gonads and this activates Stra8 to induce meiosis while male-specific gene expression is suppressed. However, it is unknown whether meiotic entry by an elevated level of RA is responsible for the suppression of male-type gene expression. To address this question, we have generated Cyp26b1/Stra8 double knockout (dKO) embryos. We successfully suppressed the induction of meiosis in CYP26B1-null XY germ cells by removing the Stra8 gene. Concomitantly, we found that the male genetic program represented by the expression of NANOS2 and DNMT3L was totally rescued in about half of dKO germ cells, indicating that meiotic entry causes the suppression of male differentiation. However, half of the germ cells still failed to enter the appropriate male pathway in the dKO condition. Using microarray analyses together with immunohistochemistry, we found that KIT expression was accompanied by mitotic activation, but was canceled by inhibition of the RA signaling pathway. Taken together, we conclude that inhibition of RA is one of the essential factors to promote male germ cell differentiation, and that CYP26B1 suppresses two distinct genetic programs induced by RA: a Stra8-dependent meiotic pathway, and a Stra8-independent mitotic pathway.

Environmental epigenetics and effects on male fertility

Environmental exposures to factors such as toxicants or nutrition can have impacts on testis biology and male fertility. The ability of these factors to influence epigenetic mechanisms in early life exposures or from ancestral exposures will be reviewed. A growing number of examples suggest environmental epigenetics will be a critical factor to consider in male reproduction.

Sox9-related signaling controls zebrafish juvenile ovary-testis transformation

In almost all vertebrates, the downstream of the sox9 signaling axis is well conserved for testis differentiation. The upstream genes of this pathway vary from species to species during evolution. Yet, little is known about how these signaling cascades are regulated and what cellular processes are dominant in ovary–testis transformation in juvenile zebrafish. In this study, we find that the transforming gonads undergo activation of sox9a-expressing stromal cells with increased deposition of extracellular matrix and formation of degenerative compartments. This leads to follicle disassembly, oocyte degeneration, follicle cell-cyp19a1a-amh conversions, and, eventually, formation of the testis cord. In vitro primary culture of juvenile ovary tissue in gonadotropins increases cytoplasmic accumulation of sox9a and p-Erk1/2, and induces mesenchymal morphology. MAPK inhibitors (MKI), a mixture of PD98059 and U0216, eliminate the cytoplasmic distribution but do not eradicate nuclear localization of sox9a and p-Erk1/2. Nuclear p53 are relatively increased in MKI-treated cells that exhibit less spreading and reduced proliferation. Despite uniform nuclear condensation, only a fraction of cells displayed the apoptotic phenotype. These results suggest that high levels of cytoplasmic sox9a and p-Erk1/2 activity activate stromal cells and enhance the production of extracellular matrix required for testis cord formation, whereas deregulation and translocation of sox9a and p-Erk1/2 induce follicle disassembly and incomplete apoptosis associated with nuclear p53. Together with the established FSH/cAMP/MAPK/AMH pathway in mammalian granulosa and Sertoli cells, we demonstrated that the sox9 axis signaling that determines testis formation in mammals also induces zebrafish ovary–testis transition, and adds to its conserved role in sex reversal.

Gene expression profile during testicular development in patients with SRY-negative 46,XX testicular disorder of sex development

OBJECTIVE

To elucidate alternative pathways in testicular development, we attempted to clarify the genetic characteristics of SRY-negative XX testes.

MATERIALS AND METHODS

We previously reported 5 cases of SRY-negative 46,XX testicular disorders of sex development and demonstrated that coordinated expression of genes such as SOX9, SOX3, and DAX1 was associated with testicular development. We performed a case-control study between the aforementioned boy with 46,XX testicular disorders of sex development and an age-matched patient with hydrocele testis (46,XY). During their consecutive surgeries, testicular biopsy specimens were obtained. Genes with differential expression compared with XY testis were identified using polymerase chain reaction (PCR)-based subtractive hybridization and sequencing. For validation of differential gene expression, real-time RT-PCR was performed using gene-specific primers. The distribution of candidate proteins in the testicular tissue was clarified by immunohistochemistry in human and rodent specimens. Moreover, in vitro inhibitory assays were performed.

RESULTS

We identified 13 upregulated and 7 downregulated genes in XX testis. Among the candidate genes, we focused on ROCK1 (Rho-associated, coiled-coil protein kinase 1) in the upregulated gene group, because high expression in XX testis was validated by real-time RT-PCR. ROCK1 protein was detected in germ cells, Leydig cells, and Sertoli cells by immunohistochemistry. Moreover, the addition of specific ROCK1 inhibitor to Sertoli cells decreased SOX9 gene expression.

CONCLUSION

On the basis of in vitro inhibitory assay, it is suggested that ROCK1 phosphorylates and activates SOX9 in Sertoli cells. Testes formation might be initiated by an alternative signaling pathway attributed to ROCK1, not SRY, activation in XX testes.

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.

Transcriptome sequencing and de novo annotation of the critically endangered Adriatic sturgeon

Background

Sturgeons are a group of Condrostean fish with very high evolutionary, economical and conservation interest. The eggs of these living fossils represent one of the most high prized foods of animal origin. The intense fishing pressure on wild stocks to harvest caviar has caused in the last decades a dramatic decline of their distribution and abundance leading the International Union for Conservation of Nature to list them as the more endangered group of species. As a direct consequence, world-wide efforts have been made to develop sturgeon aquaculture programmes for caviar production. In this context, the characterization of the genes involved in sex determination could provide relevant information for the selective farming of the more profitable females.

Results

The 454 sequencing of two cDNA libraries from the gonads and brain of one male and one female full-sib A. naccarii, yielded 182,066 and 167,776 reads respectively, which, after strict quality control, were iterative assembled into more than 55,000 high quality ESTs. The average per-base coverage reached by assembling the two libraries was 4X. The multi-step annotation process resulted in 16% successfully annotated sequences with GO terms. We screened the transcriptome for 32 sex-related genes and highlighted 7 genes that are potentially specifically expressed, 5 in male and 2 in females, at the first life stage at which sex is histologically identifiable. In addition we identified 21,791 putative EST-linked SNPs and 5,295 SSRs.

Conclusions

This study represents the first large massive release of sturgeon transcriptome information that we organized into the public database AnaccariiBase, which is freely available at http://compgen.bio.unipd.it/anaccariibase/. This transcriptomic data represents an important source of information for further studies on sturgeon species. The hundreds of putative EST-linked molecular makers discovered in this study will be invaluable for sturgeon reintroduction and breeding programs.

Characterization of sex determination and sex differentiation genes in Latimeria

Genes involved in sex determination and differentiation have been identified in mice, humans, chickens, reptiles, amphibians and teleost fishes. However, little is known of their functional conservation, and it is unclear whether there is a common set of genes shared by all vertebrates. Coelacanths, basal Sarcopterygians and unique "living fossils", could help establish an inventory of the ancestral genes involved in these important developmental processes and provide insights into their components. In this study 33 genes from the genome of Latimeria chalumnae and from the liver and testis transcriptomes of Latimeria menadoensis, implicated in sex determination and differentiation, were identified and characterized and their expression levels measured. Interesting findings were obtained for GSDF, previously identified only in teleosts and now characterized for the first time in the sarcopterygian lineage; FGF9, which is not found in teleosts; and DMRT1, whose expression in adult gonads has recently been related to maintenance of sexual identity. The gene repertoire and testis-specific gene expression documented in coelacanths demonstrate a greater similarity to modern fishes and point to unexpected changes in the gene regulatory network governing sexual development.

The downside of 'inappropriate messaging': new insight into the development of testicular germ cell tumours in young men?

How invasive testicular germ cell tumours (TGCTs) develop from precursor carcinoma in situ/intratubular germ cell neoplasia unclassified (CIS/IGCNU) cells, and only after puberty, is unknown. In the current issue of The Journal of Pathology, Jørgensen and colleagues have compared the protein expression profile of CIS before and after puberty and in pre-invasive versus invasive TGCT and show that the mitosis-meiosis controller DMRT1 switches off in CIS cells postpubertally and is associated with invasiveness. They also show that CIS cells express a 'confusing' mix of pro- and anti-meiotic proteins; this may predispose CIS cells to accumulate extra chromosomal material which ultimately leads to tumourigenesis.