Sex determination and sex reversal

Complexity of Sex Differences and Their Impact on Alzheimer's Disease

Sex differences are present in brain morphology, sex hormones, aging processes and immune responses. These differences need to be considered for proper modelling of neurological diseases with clear sex differences. This is the case for Alzheimer's disease (AD), a fatal neurodegenerative disorder with two-thirds of cases diagnosed in women. It is becoming clear that there is a complex interplay between the immune system, sex hormones and AD. Microglia are major players in the neuroinflammatory process occurring in AD and have been shown to be directly affected by sex hormones. However, many unanswered questions remain as the importance of including both sexes in research studies has only recently started receiving attention. In this review, we provide a summary of sex differences and their implications in AD, with a focus on microglia action. Furthermore, we discuss current available study models, including emerging complex microfluidic and 3D cellular models and their usefulness for studying hormonal effects in this disease.

Sex-limited chromosomes and non-reproductive traits

Sex chromosomes are typically viewed as having originated from a pair of autosomes, and differentiated as the sex-limited chromosome (e.g. Y) has degenerated by losing most genes through cessation of recombination. While often thought that degenerated sex-limited chromosomes primarily affect traits involved in sex determination and sex cell production, accumulating evidence suggests they also influence traits not sex-limited or directly involved in reproduction. Here, we provide an overview of the effects of sex-limited chromosomes on non-reproductive traits in XY, ZW or UV sex determination systems, and discuss evolutionary processes maintaining variation at sex-limited chromosomes and molecular mechanisms affecting non-reproductive traits.

Models and Molecular Markers of Spermatogonial Stem Cells in Vertebrates: To Find Models in Nonmammals

Spermatogonial stem cells (SSCs) are the germline stem cells that are essential for the maintenance of spermatogenesis in the testis. However, it has not been sufficiently understood in amphibians, reptiles, and fish because numerous studies have been focused mainly on mammals. The aim of this review is to discuss scientific ways to elucidate SSC models of nonmammals in the context of the evolution of testicular organization since rodent SSC models. To further understand the SSC models in nonmammals, we point out common markers of an SSC pool (undifferentiated spermatogonia) in various types of testes where the kinetics of the SSC pool appears. This review includes the knowledge of (1) common molecular markers of vertebrate type A spermatogonia including putative SSC markers, (2) localization of the markers on the spermatogonia that have been reported in previous studies, (3) highlighting the most common markers in vertebrates, and (4) suggesting ways of finding SSC models in nonmammals.

ASER: Animal Sex Reversal Database

Sex reversal, representing extraordinary sexual plasticity during the life cycle, not only triggers reproduction in animals but also affects reproductive and endocrine system-related diseases and cancers in humans. Sex reversal has been broadly reported in animals; however, an integrated resource hub of sex reversal information is still lacking. Here, we constructed a comprehensive database named ASER (Animal Sex Reversal) by integrating sex reversal-related data of 18 species from teleostei to mammalia. We systematically collected 40,018 published papers and mined the sex reversal-associated genes (SRGs), including their regulatory networks, from 1611 core papers. We annotated homologous genes and computed conservation scores for whole genomes across the 18 species. Furthermore, we collected available RNA-seq datasets and investigated the expression dynamics of SRGs during sex reversal or sex determination processes. In addition, we manually annotated 550 in situ hybridization (ISH), fluorescence in situ hybridization (FISH), and immunohistochemistry (IHC) images of SRGs from the literature and described their spatial expression in the gonads. Collectively, ASER provides a unique and integrated resource for researchers to query and reuse organized data to explore the mechanisms and applications of SRGs in animal breeding and human health. The ASER database is publicly available at http://aser.ihb.ac.cn/.

Gynecological Problems in Newborns and Infants

Pediatric-adolescent or developmental gynecology has been separated from general gynecology because of the unique issues that affect the development and anatomy of growing girls and young women. It deals with patients from the neonatal period until maturity. There are not many gynecological problems that can be diagnosed in newborns; however, some are typical of the neonatal period. This paper aims to discuss the most frequent gynecological issues in the neonatal period.

The Contribution of Y Chromosome Genes to Spontaneous Differentiation of Human Embryonic Stem Cells into Embryoid Bodies In Vitro

Objective

Sexual dimorphism in mammals can be described as subsequent transcriptional differences from their distinct sex chromosome complements. Following X inactivation in females, the Y chromosome is the major genetic difference between sexes. In this study, we used a male embryonic stem cell line (Royan H6) to identify the potential role of the male-specific region of the Y chromosome (MSY) during spontaneous differentiation into embryoid bodies (EBs) as a model of early embryonic development.

Materials and Methods

In this experimental study, RH6 cells were cultured on inactivated feeder layers and Matrigel. In a dynamic suspension system, aggregates were generated in the same size and were spontaneously differentiated into EBs. During differentiation, expression patterns of specific markers for three germ layers were compared with MSY genes.

Results

Spontaneous differentiation was determined by downregulation of pluripotent markers and upregulation of fourteen differentiation markers. Upregulation of the ectoderm markers was observed on days 4 and 16, whereas mesoderm markers were upregulated on the 8th day and endodermic markers on days 12-16. Mesoderm markers correlated with 8 MSY genes namely DDX3Y, RPS4Y1, KDM5D, TBL1Y, BCORP1, PRY, DAZ, and AMELY, which were classified as a mesoderm cluster. Endoderm markers were co-expressed with 7 MSY genes, i.e. ZFY, TSPY, PRORY, VCY, EIF1AY, USP9Y, and RPKY, which were grouped as an endoderm cluster. Finally, the ectoderm markers correlated with TXLNGY, NLGN4Y, PCDH11Y, TMSB4Y, UTY, RBMY1, and HSFY genes of the MSY, which were categorized as an ectoderm cluster. In contrast, 2 MSY genes, SRY and TGIF2LY, were more highly expressed in RH6 cells compared to EBs.

Conclusion

We found a significant correlation between spontaneous differentiation and upregulation of specific MSY genes. The expression alterations of MSY genes implied the potential responsibility of their gene co-expression clusters for EB differentiation. We suggest that these genes may play important roles in early embryonic development.

Human Umbilical Cord: Information Mine in Sex-Specific Medicine

Biological differences between sexes should be considered in all stages of research, as sexual dimorphism starts in utero leading to sex-specific fetal programming. In numerous biomedical fields, there is still a lack of stratification by sex despite primary cultured cells retaining memory of the sex and of the donor. The sex of donors in biological research must be known because variations in cells and cellular components can be used as endpoints, biomarkers and/or targets of pharmacological studies. This selective review focuses on the current findings regarding sex differences observed in the umbilical cord, a widely used source of research samples, both in the blood and in the circulating cells, as well as in the different cellular models obtainable from it. Moreover, an overview on sex differences in fetal programming is reported. As it emerges that the sex variable is still often forgotten in experimental models, we suggest that it should be mandatory to adopt sex-oriented research, because only awareness of these issues can lead to innovative research.

A framework for high-resolution phenotyping of candidate male infertility mutants: from human to mouse

Male infertility is a heterogeneous condition of largely unknown etiology that affects at least 7% of men worldwide. Classical genetic approaches and emerging next-generation sequencing studies support genetic variants as a frequent cause of male infertility. Meanwhile, the barriers to transmission of this disease mean that most individual genetic cases will be rare, but because of the large percentage of the genome required for spermatogenesis, the number of distinct causal mutations is potentially large. Identifying bona fide causes of male infertility thus requires advanced filtering techniques to select for high-probability candidates, including the ability to test causality in animal models. The mouse remains the gold standard for defining the genotype-phenotype connection in male fertility. Here, we present a best practice guide consisting of (a) major points to consider when interpreting next-generation sequencing data performed on infertile men, and, (b) a systematic strategy to categorize infertility types and how they relate to human male infertility. Phenotyping infertility in mice can involve investigating the function of multiple cell types across the testis and epididymis, as well as sperm function. These findings will feed into the diagnosis and treatment of male infertility as well as male health broadly.

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.

Lessons from human umbilical cord: gender differences in stem cells from Wharton's jelly

OBJECTIVE

To study the molecular features of mesenchymal stem cells from Wharton Jelly (WJ-MSCs) of umbilical cord to predict their differentiation capacity.

DESIGN

Comparison of gene expression from mesenchymal stem cells of male and female umbilical cord SETTING: University hospital PATIENT (S): umbilical cords (n = 12, 6 males and 6 females) retrieved from spontaneous full-term vaginal delivery of healthy women INTERVENTION: we analyzed the expression of the stemness related genes C-MYC, OCT4, SOX2 and NANOG and of the epigenetic modulating gene DNA-methyltransferase 1 (DNMT1).

MEAN OUTCOME MEASURE

WJ-MSCs were isolated by standard procedures and immunophenotypically characterized. Gene expression analysis of stemness related genes and the epigenetic modulating gene DNMT1 were performed by real-time PCR RESULTS: expression of the OCT4 and DNMT1 genes was significantly higher in WJ- MSCs isolated from male subjects, as compared to MSCs isolated from female-derived WJ. The resulting higher expression of OCT4 and DNMT1 in WJ-MSCs from males as compared with female WJ-MSCs for the first time identifies a specific relationship between stemness genes, an epigenetic modulator, and gender differences.

CONCLUSION

our findings disclose novel biomedical implications in WJ-MSCs related to the sex of the donor, thus providing additional cues to exploit their regenerative potential in allogenic transplantation.

The Reversible Sex of Gonochoristic Fish: Insights and Consequences

Fish sex reversal is a means to understand sex determination and differentiation, but it is also used to control sex in aquaculture. This review discusses sex reversal in gonochoristic fish, with the coexistence of genetic and environmental influences. The different periods of fish sensitivity to sex reversal treatments are presented with the mechanisms implicated. The old players of sex differentiation are revisited with transcriptome data and loss of function studies following hormone- or temperature-induced sex reversal. We also discuss whether cortisol is the universal mediator of sex reversal in fish due to its implication in ovarian meiosis and 11KT increase. The large plasticity in fish for sex reversal is also evident in the brain, with a reversibility existing even in adulthood. Studies on epigenetics are presented, since it links the environment, gene expression, and sex reversal, notably the association of DNA methylation in sex reversal. Manipulations with exogenous factors reverse the primary sex in many fish species under controlled conditions, but several questions arise on whether this can occur under wild conditions and what is the ecological significance. Cases of sex reversal in wild fish populations are shown and their fitness and future perspectives are discussed.

XX testicular disorder of sex differentiation: case report

The 46 XX, testicular sex differentiation disorder, or XX male syndrome, is a rare condition detected by cytogenetics, in which testicular development occurs in the absence of the Y chromosome. It occurs in 1:20,000 to 25,000 male newborns and represents 2% of cases of male infertility. About 90% of individuals present with normal phenotype at birth and are generally diagnosed after puberty for hypoganadism, gynecomastia, and/or infertility. The authors present the report of an XX male with complete masculinization and infertility.

Disorders of sex development: a genetic study of patients in a multidisciplinary clinic

Sex development is a process under genetic control directing both the bi-potential gonads to become either a testis or an ovary, and the consequent differentiation of internal ducts and external genitalia. This complex series of events can be altered by a large number of genetic and non-genetic factors. Disorders of sex development (DSD) are all the medical conditions characterized by an atypical chromosomal, gonadal, or phenotypical sex. Incomplete knowledge of the genetic mechanisms involved in sex development results in a low probability of determining the molecular definition of the genetic defect in many of the patients. In this study, we describe the clinical, cytogenetic, and molecular study of 88 cases with DSD, including 29 patients with 46,XY and disorders in androgen synthesis or action, 18 with 46,XX and disorders in androgen excess, 17 with 46,XY and disorders of gonadal (testicular) development, 11 classified as 46,XX other, eight with 46,XX and disorders of gonadal (ovarian) development, and five with sex chromosome anomalies. In total, we found a genetic variant in 56 out of 88 of them, leading to the clinical classification of every patient, and we outline the different steps required for a coherent genetic testing approach. In conclusion, our results highlight the fact that each category of DSD is related to a large number of different DNA alterations, thus requiring multiple genetic studies to achieve a precise etiological diagnosis for each patient.

Sex determination in insects: variations on a common theme

Recent studies in a representative selection of holometabolous insects suggest that, despite diversity at the instructive level, the signal-relaying part of the sex-determining pathway is remarkably well conserved. In principle, it is composed of the transformer gene (tra), which acts as a common binary switch that transduces the selected sexual fate, female when ON, male when OFF, to the downstream effector doublesex(dsx) that controls overt sexual differentiation. An interesting recurrent feature is that tra is switched ON in the early zygote by maternally provisioned tra activity. Different male-determining signals evolved, which prevent maternal activation of zygotic tra to allow for male development. In some species, where lack of maternal activation leaves tra in the OFF state, novel female-determining signals were deployed to activate zygotic tra. It appears that both the instructive end of the pathway upstream of tra as well as the executive end downstream of dsx are primary targets of evolutionary divergence, while the transduction part seems less prone to changes. We propose that this is a feature shared with many other signaling cascades that regulate developmental fates.

Duplication of dosage sensitive sex reversal area in a 46, XY patient with normal sex determining region of Y causing complete sex reversal

BACKGROUND

The sex chromosome composition of the primordial gonad, either 46XX or 46XY, determines its differentiation as ovaries or testes. Local hormones secreted by developing gonads and tissue specific transcription factors influence the differentiation of external and internal genital structures. Dosage sensitive sex reversal adrenal hypoplasia congenita critical region (DAX1) on Xp21 is a gene which is expressed in the developing adrenals, gonads, hypothalamus and pituitary gland. Duplication of this area causes dosage sensitive male-to-female sex reversal while mutation or deletion leads to adrenal hypoplasia congenita with hypogonadotropic hypogonadism in affected males.

AIM

To report a case with duplication of the X chromosome segment within the region of Xp21.1-22.2 resulting in 46 XY sex reversal and a literature review on DAX1 and dosage sensitive sex reversal (DSS).

METHODS AND RESULTS

We present the clinical history, physical findings, laboratory, and imaging study results in a newborn baby. This infant was sex assigned as female at birth and had normal female external genitalia. Chromosome analysis was done due to multiple minor malformations and showed a karyotype of 46 Xp+Y. Fluorescent in situ hybridization analysis revealed the duplication in the DSS area.

CONCLUSION

Duplication of the DAX1 gene on the X chromosome with normal sex determining region of Y (SRY) results in 46 XY sex reversal. This was inherited from the mother who had normal ovarian function. Additional problems include growth failure, mental retardation and multiple congenital anomalies. The baby did not have a mutation or deletion of DAX1, which would have caused adrenal insufficiency and hypogonadism.

Identification of novel SRY mutations and SF1 (NR5A1) changes in patients with pure gonadal dysgenesis and 46,XY karyotype

Primary amenorrhea due to 46,XY disorders of sexual development (DSD) is complex with the involvement of several genes. Karyotyping of such patients is important as they may develop dysgerminoma and molecular analysis is important to identify the underlying mechanism and explore the cascade of events occurring during sexual development. The present study was undertaken for the genetic analysis in seven patients from five families presenting with primary amenorrhea and diagnosed with pure gonadal dysgenesis. Karyotyping was done and the patients were screened for underlying changes in SRY, desert hedgehog (DHH), DAX1 (NR0B1) and SF1 (NR5A1) genes, mutations in which are implicated in DSD. All the patients had 46,XY karyotype and two novel SRY mutations were found. In Family 1 (Patient S1.1) a missense mutation c.294G>A was seen, which results in a stop codon at the corresponding amino acid (Trp98X) and in Family 2 (Patients S2.1, S2.2 and S2.3), a missense mutation c.334G>A (Glu112Leu) was identified in all affected sisters. Both mutations were seen to occur in the conserved high mobility group box of SRY gene. One heterozygous change c.427G>A resulting in Glu143Lys in DHH gene in one patient and two heterozygous changes in the intronic region of SF1 (NR5A1) gene (c.244+80G>A+ c.1068-20C>T) in another patient were noted. One individual did not show changes in any of the genes analyzed. These results reiterate the importance of SRY and others, such as SF1 (NR5A1) and DHH, that are involved in the cascade of events leading to sex determination and also their role in sex reversal.

Array-CGH analysis in patients with syndromic and non-syndromic XY gonadal dysgenesis: evaluation of array CGH as diagnostic tool and search for new candidate loci

BACKGROUND

XY gonadal dysgenesis (XY-GD) is a heterogeneous disorder characterized by failure of testicular development despite a normal male karyotype. Non-syndromic and syndromic forms can be delineated. Currently, only a minority of cases can be explained by gene mutations.

METHODS

The aim of this study was to detect microdeletions and duplications by using high-resolution Agilent oligonucleotide arrays in a cohort of 87 patients with syndromic or non-syndromic 46,XY-GD.

RESULTS

In 26 patients, we identified gains or losses in regions including genes involved in XY-GD (DMRT1, SOX9, DAX1) or in regions, which have not been described as polymorphic copy number variants (CNVs).

CONCLUSIONS

This study shows that array comparative genomic hybridization (CGH) analysis is a useful tool for the molecular diagnosis of XY-GD as well as for the identification of potential candidate genes involved in male sexual development.

A novel sex determination system in a close relative of the house mouse

Therian mammals have an extremely conserved XX/XY sex determination system. A limited number of mammal species have, however, evolved to escape convention and present aberrant sex chromosome complements. In this study, we identified a new case of atypical sex determination in the African pygmy mouse Mus minutoides, a close evolutionary relative of the house mouse. The pygmy mouse is characterized by a very high proportion of XY females (74%, n = 27) from geographically widespread Southern and Eastern African populations. Sequencing of the high mobility group domain of the mammalian sex determining gene Sry, and karyological analyses using fluorescence in situ hybridization and G-banding data, suggest that the sex reversal is most probably not owing to a mutation of Sry, but rather to a chromosomal rearrangement on the X chromosome. In effect, two morphologically different X chromosomes were identified, one of which, designated X*, is invariably associated with sex-reversed females. The asterisk designates the still unknown mutation converting X*Y individuals into females. Although relatively still unexplored, such an atypical sex chromosome system offers a unique opportunity to unravel new genetic interactions involved in the initiation of sex determination in mammals.

Sequential SDF1a and b-induced mobility guides Medaka PGC migration

Assembly and formation of the gonad primordium are the first steps toward gonad differentiation and subsequent sex differentiation. Primordial germ cells (PGCs) give rise to the gametes that are responsible for the development of a new organism in the next generation. In many organisms, following their specification the germ cells migrate toward the location of the prospective gonadal primordium. To accomplish this, the PGCs obtain directional cues from cells positioned along their migration path. One such cue, the chemokine SDF1 (stromal cell-derived factor 1) and its receptor CXCR4 have recently been found to be critical for proper PGC migration in zebrafish, chick and mouse. We have studied the mechanisms responsible for PGC migration in Medaka. In contrast to the situation observed in zebrafish, where proper PGC positioning is the result of active migration in the direction of the source of SDF1a, Medaka PGC movements are shown to be the consequence of a combination of active SDF1a and SDF1b-guided migration. In this process both SDF1 co-orthologues show only partly overlapping expression pattern and cooperate in the correct positioning of the PGCs.

Male-to-female sex reversal associated with an ∼250 kb deletion upstream of NR0B1 (DAX1)

Deletion of the dosage sensitive gene NR0B1 encoding DAX1 on chromosome Xp21.2 results in congenital adrenal hypoplasia (AHC), whereas NR0B1 duplication in 46,XY individuals leads to gonadal dysgenesis and a female phenotype. We describe a 21-year-old 46,XY female manifesting primary amenorrhea, a small immature uterus, gonadal dysgenesis, and notably absent adrenal insufficiency with a submicroscopic (257 kb) deletion upstream of NR0B1. We hypothesize that loss of regulatory sequences may have resulted in position effect up-regulation of DAX1 expression, consistent with phenotypic consequences of NR0B1 duplication. We propose that this genomic region and by extension those surrounding the dosage sensitive SRY, SOX9, SF1, and WNT-4 genes, should be examined for copy-number variation in patients with sex reversal.