Sex determination and gonadal development in mammals

Tissue clearing and imaging approaches for in toto analysis of the reproductive system†

New microscopy techniques in combination with tissue clearing protocols and emerging analytical approaches have presented researchers with the tools to understand dynamic biological processes in a three-dimensional context. This paves the road for the exploration of new research questions in reproductive biology, for which previous techniques have provided only approximate resolution. These new methodologies now allow for contextualized analysis of far-larger volumes than was previously possible. Tissue optical clearing and three-dimensional imaging techniques posit the bridging of molecular mechanisms, macroscopic morphogenic development, and maintenance of reproductive function into one cohesive and comprehensive understanding of the biology of the reproductive system. In this review, we present a survey of the various tissue clearing techniques and imaging systems, as they have been applied to the developing and adult reproductive system. We provide an overview of tools available for analysis of experimental data, giving particular attention to the emergence of artificial intelligence-assisted methods and their applicability to image analysis. We conclude with an evaluation of how novel image analysis approaches that have been applied to other organ systems could be incorporated into future experimental evaluation of reproductive biology.

Two redundant transcription factor binding sites in a single enhancer are essential for mammalian sex determination

Male development in mammals depends on the activity of the two SOX gene: Sry and Sox9, in the embryonic testis. As deletion of Enhancer 13 (Enh13) of the Sox9 gene results in XY male-to-female sex reversal, we explored the critical elements necessary for its function and hence, for testis and male development. Here, we demonstrate that while microdeletions of individual transcription factor binding sites (TFBS) in Enh13 lead to normal testicular development, combined microdeletions of just two SRY/SOX binding motifs can alone fully abolish Enh13 activity leading to XY male-to-female sex reversal. This suggests that for proper male development to occur, these few nucleotides of non-coding DNA must be intact. Interestingly, we show that depending on the nature of these TFBS mutations, dramatically different phenotypic outcomes can occur, providing a molecular explanation for the distinct clinical outcomes observed in patients harboring different variants in the same enhancer.

Maternal nutrition and fetal imprinting of the male progeny

The global population as well as the demand for human food is rapidly growing worldwide, which necessitates improvement of efficiency in livestock operations. In this context, environmental factors during fetal and/or neonatal life have been observed to influence normal physical and physiological function of an individual during adulthood, and this phenomenon is called fetal or developmental programming. While numerous studies have reported the impact of maternal factors on development of the female progeny, limited information is available on the potential effects of fetal programming on reproductive function of the male offspring. Therefore, the objective for this review article was to focus on available literature regarding the impact of maternal factors, particularly maternal nutrition, on reproductive system of the male offspring. To this end, we highlighted developmental programming of the male offspring in domestic species (i.e., pig, cow and sheep) as well as laboratory species (i.e., mice and rat) during pregnancy and lactation. In this sense, we pointed out the effects of maternal nutrition on various functions of the male offspring including hypothalamic-pituitary axis, hormonal levels, testicular tissue and semen parameters.

Anxiety mediates association between sex and jaw function limitation in temporomandibular disorder patients from China

Aim

The objective of this study is to explore the relationship between sex and jaw function and to test whether anxiety mediates the causal relationship between sex and jaw function in temporomandibular disorders (TMDs) patients.

Methods

A total of 488 participants with TMD were included in the analysis. Demographic data were collected. Generalized anxiety symptoms and anxiety severity were initially assessed using the GAD-7 questionnaire. And jaw function limitation was measured using the JFLS-8 scale. A directed acyclic graph (DAG) was used in this study to evaluate the hypotheses. Mediation analysis was conducted to explore causality and to calculate the total effect, natural direct effect (NDE) and natural indirect effect (NIE).

Results

In TMD patients, there was a significant association between female and jaw function (r = 0.17, p < 0.001), female and anxiety (r = 0.15, p = 0.002), anxiety and jaw function (r = 0.35, p < 0.001). In addition, sex can directly lead to differences in impaired jaw function (NDE: 3.719, 95% CI: 1.619-5.828, p < 0.001), and can also be causally related to jaw function through anxiety (NIE: 1.146, 95% CI: 0.267-2.024, p = 0.011). And the total effect was 4.865 (95% CI, 2.709-7.029, p < 0.001).

Conclusion

A causal mechanism was found that anxiety acts as a mediator of sex effects on jaw function. Therefore, psychological factors need to be taken into account in the treatment of female TMD patients. Further clinical trials are needed to explore whether psychotherapy is more beneficial to improve jaw function in female TMD patients.

Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review

In mammals, gonadal somatic cell lineage differentiation determines the development of the bipotential gonad into either the ovary or testis. Sertoli cells, the only somatic cells in the spermatogenic tubules, support spermatogenesis during gonadal development. During embryonic Sertoli cell lineage differentiation, relevant genes, including WT1, GATA4, SRY, SOX9, AMH, PTGDS, SF1, and DMRT1, are expressed at specific times and in specific locations to ensure the correct differentiation of the embryo toward the male phenotype. The dysregulated development of Sertoli cells leads to gonadal malformations and male fertility disorders. Nevertheless, the molecular pathways underlying the embryonic origin of Sertoli cells remain elusive. By reviewing recent advances in research on embryonic Sertoli cell genesis and its key regulators, this review provides novel insights into sex determination in male mammals as well as the molecular mechanisms underlying the genealogical differentiation of Sertoli cells in the male reproductive ridge.

Semen sexing and its impact on fertility and genetic gain in cattle

Semen sexing is among one of the most remarkable inventions of the past few decades in the field of reproductive biotechnology. The urge to produce offspring of a desired sex has remained since traditional times. Researchers have tried many methods for accurate semen sexing, but only the flow cytometry method has proved to be effective for commercial utilization. However, there were always concerns about the effects of sexed semen, especially on fertility and the rate of genetic gain. Some concerns were genuine because of factors such as low semen dosage in sexed semen straws and damage to sperm during the sorting process. Various researchers have conducted numerous studies to find out the effect of sexed semen on fertility and, in this article, we reflect on their findings. Initially, there were comparatively much lower conception rates (∼70% of conventional semen) but, with refinement in technology, this gap is bridging and the use of sexed semen will increase over time. Concerning genetic gain with use of sexed semen, a positive effect on rate of genetic progress with the use of sexed semen has been observed based on various simulation studies, although there has been a mild increase in inbreeding.

Comparison of the gene expression profile of testicular tissue before and after sexual maturity in Qianbei Ma goats

BACKGROUND

With long-term research on the reproductive ability of Qianbei Ma goat, we found that the puberty of the male goats comes at the age of 3 months and reaches sexual maturity at 4 months,the male goats are identified as physically mature at 9 months and able to mate. Compared with other kinds of breeds of goats, Qianbei Ma goat is featured with more faster growth and earlier sexual maturity.Therefore, in order to explore the laws of growth of Qianbei Ma goat before sexual maturity(3-month-old)and after sexual maturity (9-month-old). The testicular tissue was collected to explore their changes in morphology through HE staining, the serum was collected to detect the hormone content, and the mRNA expression profile of the testis was analyzed by transcriptomics. In this way, the effect of testicular development on the reproduction of Qianbei ma goats was further analyzed.

RESULTS

The results showed that the area and diameter of spermatogenic tubules were larger at 9 months than 3 months, and the number of spermatocytes, interstitial cells, spermatogonia and secondary spermatocytes in the lumen of the tubules showed a similar trend. The appearance of spermatozoa at age 3 months indicated that puberty had begun in Qianbei Ma goats. The Elasa test for testosterone, luteinizing hormone, follicle stimulating hormone and anti-Müllerian hormone showed that the levels of these hormones in the serum at age 9 months were all highly significantly different than those at age 3 months (P < 0.01). There were 490 differentially expressed genes (DEGs) between the (|log2(fold change)| > 1 and p value < 0.05) 3-month-old and 9-month-old groups, of which 233 genes were upregulated and 257 genes were downregulated (3 months of age was used as the control group and 9 months of age was used as the experimental group). According to the GO and KEGG enrichment analyses of DEGs, PRSS58, ECM1, WFDC8 and LHCGR are involved in testicular development and androgen secretion, which contribute to the sexual maturation of Qianbei Ma goats.

CONCLUSIONS

Potential biomarker genes and relevant pathways involved in the regulation of testicular development and spermatogenesis in Qianbei Ma goats were identified, providing a theoretical basis and data support for later studies on the influence of testicular development and spermatogenesis before and after sexual maturity in Qianbei Ma goats.

Development Features on the Selection of Animal Models for Teratogenic Testing

Today, the use of animal models from different species continues to represent a fundamental step in teratogenic testing, despite the increase in alternative solutions that provide an important screening to the enormous quantity of new substances that aim to enter the market every year. The maintenance of these models is due to the sharing of similar development processes with humans, and in this way they represent an important contribution to the safety in the use of the compounds tested. Furthermore, the application of advances in embryology to teratology, although hampered by the complexity of reproductive processes, continues to prove the importance of sensitivity during embryonic and fetal development to detect potential toxicity, inducing mortality/abortion and malformations.In this chapter, essential periods of development in different models are outlined, highlighting the similarities and differences between species, the advantages and disadvantages of each group, and specific sensitivities for teratogenic testing. Models can be divided into invertebrate species such as earthworms of the species Eisenia fetida/Eisenia andrei, Caenorhabditis elegans, and Drosophila melanogaster, allowing for rapid results and minor ethical concerns. Vertebrate nonmammalian species Xenopus laevis and Danio rerio are important models to assess teratogenic potential later in development with fewer ethical requirements. Finally, the mammalian species Mus musculus, Rattus norvegicus, and Oryctolagus cuniculus, phylogenetically closer to humans, are essential for the assessment of complex specialized processes, occurring later in development.Regulations for the development of toxicology tests require the use of mammalian species. Although ethical concerns and costs limit their use in large-scale screening. On the other hand, invertebrate and vertebrate nonmammalian species are increasing as alternative animal models, as these organisms combine low cost, less ethical requirements, and culture conditions compatible with large-scale screening. Their main advantage is to allow high-throughput screening in a whole-animal context, in contrast to the in vitro techniques, not dependent on the prior identification of a target. Better knowledge of the development pathways of animal models will allow to maximize human translation and reduce the number of animals used, leading to a selection of compounds with an improved safety profile and reduced time to market for new drugs.

Defining the cellular complexity of the zebrafish bipotential gonad

Zebrafish are routinely used to model reproductive development, function, and disease, yet we still lack a clear understanding of the fundamental steps that occur during early bipotential gonad development, including when endothelial cells, pericytes, and macrophage arrive at the bipotential gonad to support gonad growth and differentiation. Here, we use a combination of transgenic reporters and single-cell sequencing analyses to define the arrival of different critical cell types to the larval zebrafish gonad. We determined that blood initially reaches the gonad via a vessel formed from the swim bladder artery, which we have termed the gonadal artery. We find that vascular and lymphatic development occurs concurrently in the bipotential zebrafish gonad and our data suggest that similar to what has been observed in developing zebrafish embryos, lymphatic endothelial cells in the gonad may be derived from vascular endothelial cells. We mined preexisting sequencing datasets to determine whether ovarian pericytes had unique gene expression signatures. We identified 215 genes that were uniquely expressed in ovarian pericytes, but not expressed in larval pericytes. Similar to what has been shown in the mouse ovary, our data suggest that pdgfrb+ pericytes may support the migration of endothelial tip cells during ovarian angiogenesis. Using a macrophage-driven photoconvertible protein, we found that macrophage established a nascent resident population as early as 12 dpf and can be observed removing cellular material during gonadal differentiation. This foundational information demonstrates that the early bipotential gonad contains complex cellular interactions, which likely shape the health and function of the mature gonad.

Preimplantation embryo exposure to ketone bodies exerts sex-specific effects on mouse fetal and placental transcriptomes

RESEARCH QUESTION

Does in vitro exposure of preimplantation mouse embryos to the ketone bodies β-hydroxybutyrate (βOHB) and acetoacetate (AcAc) impact post-transfer fetal and placental gene expression?

DESIGN

Blastocysts cultured in vitro with or without 2 mmol/l βOHB alone ('βOHB') or combined with 0.8 mmol/l AcAc ('Keto') underwent embryo transfer. Transcriptional profiles of sexed placenta, liver and brain at gestational day 14.5 were examined via RNA sequencing and DAVID functional analysis.

RESULTS

A sexually dimorphic response to in vitro ketone exposure was observed. Both βOHB and Keto exposure down-regulated genes related to oxidative phosphorylation specifically in female liver. βOHB down-regulated female placental steroid biosynthetic processes, while Keto treatment up-regulated genes relevant to blood vessel formation and cell migration in male placenta. Brain transcriptomes were minimally affected. X-linked genes and chromatin modifiers were identified as differentially expressed in both liver and placenta, alluding to a sex-specific regulatory mechanism.

CONCLUSIONS

Transient preimplantation ketone exposure perturbs sex-specific fetal liver and placental gene expression, demonstrating a developmental programming effect that warrants future investigation of the postnatal metabolic health of male and female offspring.

L1cam alternative shorter transcripts encoding the extracellular domains were overexpressed in the intestine of L1cam knockdown mice

Hirschsprung disease (HSCR) is a congenital disorder of functional bowel obstruction due to the absence of enteric ganglia in distal bowel. Different L1cam variants were reportedly associated with L1cam syndrome and HSCR, whose phenotypes lacked predictable relevance to their genotypes. Using next-generation sequencing (NGS), we found an L1CAM de novo frameshift mutation in a female with mild hydrocephalus and skip-type HSCR. A nearly identical L1cam variant was introduced into FVB/NJ mice via the CRISPR-EZ method. A silent mutation was created via ssODN to gain an artificial Ncol restriction enzyme site for easier genotyping. Six L1cam protein-coding alternative transcripts were quantitatively measured. Immunofluorescence staining with polyclonal and monoclonal L1cam antibodies was used to characterize L1cam isoform proteins in enteric ganglia. Fifteen mice, seven males and eight females, generated via CRISPR-EZ, were confirmed to carry the L1cam frameshift variant, resulting in a premature stop codon. There was no prominent hydrocephalus nor HSCR-like presentation in these mice, but male infertility was noticed after observation for three generations in a total of 176 mice. Full-length L1cam transcripts were detected at a very low level in the intestinal tissues and almost none in the brain of these mice. Alternative shorter transcripts encoding the extracellular domains were overexpressed in the intestine of L1cam knockdown mice. Immunofluorescence confirmed no fulllength L1cam protein in enteric ganglia. These shorter L1cam isoform proteins might play a role in protecting L1cam knockdown mice from HSCR.

A case of 46,XY complete gonadal dysgenesis with a novel missense variant in SRY

Disorders of sex development (DSD) with mild external genital abnormalities may be diagnosed after puberty. Here, we report a case of 46,XY complete gonadal dysgenesis with a novel missense variant in sex-determining region Y (SRY), diagnosed after primary amenorrhea. A 15-yr-old patient presented to our gynecology department with a chief complaint of amenorrhea. The patient was diagnosed with a 46,XY karyotype, and SRY gene positivity. Gonadotropin levels were high, whereas testosterone levels were low. A pelvic magnetic resonance imaging (MRI) revealed a hypoplastic uterus; however, no gonads could be identified. Laparoscopy revealed bilateral streak gonads, fallopian tube-like structures, and the uterus. The gonads were removed based on the risk of gonadal malignancy. Comprehensive genetic analysis of DSD revealed a previously unreported SRY variant, c.271A>T, p.Ser91Cys, and in silico analysis predicted the variant to be pathogenic. The patient was diagnosed with 46,XY complete gonadal dysgenesis with a novel missense variant in SRY. The patient continued female hormone replacement therapy and experienced breast enlargement and cyclic menstruation. Determining the etiology of DSD can be difficult, causing anxiety in patients and their families. In addition to surgical scrutiny, genetic analysis is important to aid in diagnosis and reassure patients and their families.

Defining the cellular complexity of the zebrafish bipotential gonad

Zebrafish are routinely used to model reproductive development, function, and disease, yet we still lack a clear understanding of the fundamental steps that occur during early bipotential gonad development, including when endothelial cells, pericytes, and macrophage cells arrive at the bipotential gonad to support gonad growth and differentiation. Here, we use a combination of transgenic reporters and single-cell sequencing analyses to define the arrival of different critical cell types to the larval zebrafish gonad. We determined that blood initially reaches the gonad via a vessel formed from the swim bladder artery, which we have termed the gonadal artery. We find that vascular and lymphatic development occurs concurrently in the bipotential zebrafish gonad and our data suggest that similar to what has been observed in developing zebrafish embryos, lymphatic endothelial cells in the gonad may be derived from vascular endothelial cells. We mined preexisting sequencing data sets to determine whether ovarian pericytes had unique gene expression signatures. We identified 215 genes that were uniquely expressed in ovarian pericytes that were not expressed in larval pericytes. Similar to what has been shown in the mouse ovary, our data suggest that pdgfrb+ pericytes may support the migration of endothelial tip cells during ovarian angiogenesis. Using a macrophage-driven photoconvertible protein, we found that macrophage established a nascent resident population as early as 12 dpf and can be observed removing cellular material during gonadal differentiation. This foundational information demonstrates that the early bipotential gonad contains complex cellular interactions, which likely shape the health and function of the mature, differentiated gonad.

PRC1 suppresses a female gene regulatory network to ensure testicular differentiation

Gonadal sex determination and differentiation are controlled by somatic support cells of testes (Sertoli cells) and ovaries (granulosa cells). In testes, the epigenetic mechanism that maintains chromatin states responsible for suppressing female sexual differentiation remains unclear. Here, we show that Polycomb repressive complex 1 (PRC1) suppresses a female gene regulatory network in postnatal Sertoli cells. We genetically disrupted PRC1 function in embryonic Sertoli cells after sex determination, and we found that PRC1-depleted postnatal Sertoli cells exhibited defective proliferation and cell death, leading to the degeneration of adult testes. In adult Sertoli cells, PRC1 suppressed specific genes required for granulosa cells, thereby inactivating the female gene regulatory network. Chromatin regions associated with female-specific genes were marked by Polycomb-mediated repressive modifications: PRC1-mediated H2AK119ub and PRC2-mediated H3K27me3. Taken together, this study identifies a critical Polycomb-based mechanism that suppresses ovarian differentiation and maintains Sertoli cell fate in adult testes.

Authentic gender development in non-binary children

At present, the conceptualization of gender as a spectrum as well as non-binary identities have become increasingly visible and embraced. We are using non-binary as an umbrella term that refers to individuals who self-identify as a gender outside the gender binary, and/or who do not identify as always and completely being just a man or a woman. Our goal is to begin to create a framework for understanding gender development in non-binary children ages 0 to 8, since previous models have operated on cissupremacist assumptions, not applicable to non-binary people. As there is virtually no empirical data on the subject, we conducted a thorough literature review of current gender development theories and used our positionality as non-binary researchers to postulate two minimum criteria for non-binary gender identification: that a child learns about the existence of non-binary identities, and that they do not identify with the definitions they have been taught of what a boy or girl is. Children can learn about non-binary identities through media and knowledgeable community members and can develop "gender traits" authentically and come to identify as non-binary through biological predispositions, parental support, modeling, and being in peer groups that are supportive of identity exploration. Yet, children are not simply a product of their nature and nurture, as evidence has shown that humans are active agents in their gender development from a young age.

A case of hermaphroditism in the gonochoristic sea urchin, Strongylocentrotus purpuratus, reveals key mechanisms of sex determination†

Sea urchins are usually gonochoristic, with all of their five gonads either testes or ovaries. Here, we report an unusual case of hermaphroditism in the purple sea urchin, Strongylocentrotus purpuratus. The hermaphrodite is self-fertile, and one of the gonads is an ovotestis; it is largely an ovary with a small segment containing fully mature sperm. Molecular analysis demonstrated that each gonad producedviable gametes, and we identified for the first time a somatic sex-specific marker in this phylum: Doublesex and mab-3 related transcription factor 1 (DMRT1). This finding also enabled us to analyze the somatic tissues of the hermaphrodite, and we found that the oral tissues (including gut) were out of register with the aboral tissues (including tube feet) enabling a genetic lineage analysis. Results from this study support a genetic basis of sex determination in sea urchins, the viability of hermaphroditism, and distinguish gonad determination from somatic tissue organization in the adult.

Human organoid systems in modeling reproductive tissue development, function, and disease

Research focused on human reproductive biology has primarily relied upon clinical samples affording mainly descriptive studies with limited implementation of functional or mechanistic understanding. More importantly, restricted access to human embryonic material has necessitated the use of animals, primarily rats and mice, and short-term primary cell cultures derived from human patient material. While reproductive developmental processes are generally conserved across mammals, specific features unique to human reproduction have resulted in the development of human-based in vitro systems designed to retain or recapitulate key molecular and cellular processes important in humans. Of note, major advances in 3D epithelial stem cell-based systems modeling human reproductive organ development have been made. These cultures, broadly referred to as organoids, enable research aimed at understanding cellular hierarchies and processes controlling cellular differentiation and function. Moreover, organoids allow the pre-clinical testing of pharmacological substances, both from safety and efficacy standpoints, and hold large potential in driving aspects of personalized medicine that were previously not possible with traditional models. In this mini-review, we focus on summarizing the current state of regenerative organoid culture systems of the female and male reproductive tracts that model organ development, maintenance, and function. Specifically, we will introduce stem cell-based organoid models of the ovary/fallopian tube, endometrium, cervix, prostate gland, and testes. We will also describe organoid systems of the pre-implanting blastocyst and trophoblast, as the blastocyst and its extraembryonic trophectoderm are central to fetal, maternal, and overall pregnancy health. We describe the foundational studies leading to their development and outline the utility as well as specific limitations that are unique and common to many of these in vitro platforms.

A clue to the etiology of disorders of sex development from identity-by-descent analysis in dogs with cryptic relatedness

Disorders of sex development (DSDs) are discrepancies between sex chromosomes and phenotypical sex. Quite common forms of DSD in canine populations include testicular and ovotesticular XX DSDs with a normal set of sex chromosomes. The objective of this study was to identify genes and putative harmful variants for canine XX DSDs. I have reanalyzed data from the whole-genome sequencing of 11 XX DSD French Bulldogs and six XX DSD American Staffordshire Terriers. Identity-by-descent analysis revealed cryptic relatedness in affected French Bulldogs. Causative genes were sought in chromosomal segments shared identical-by-descent by close relatives. In French Bulldogs, the reanalysis identified 19 regions of importance with a total length of just 65.9 Mb. Variant filtering within the regions implicated AKAP2, PIWIL1, POLR3A and SH2D4B as genes that may be involved in individual cases of testicular and ovotesticular XX DSD in French Bulldogs and American Staffordshire Terriers.

Evolution of sex determination in crustaceans

Sex determination (SD) involves mechanisms that determine whether an individual will develop into a male, female, or in rare cases, hermaphrodite. Crustaceans harbor extremely diverse SD systems, including hermaphroditism, environmental sex determination (ESD), genetic sex determination (GSD), and cytoplasmic sex determination (e.g., Wolbachia controlled SD systems). Such diversity lays the groundwork for researching the evolution of SD in crustaceans, i.e., transitions among different SD systems. However, most previous research has focused on understanding the mechanism of SD within a single lineage or species, overlooking the transition across different SD systems. To help bridge this gap, we summarize the understanding of SD in various clades of crustaceans, and discuss how different SD systems might evolve from one another. Furthermore, we review the genetic basis for transitions between different SD systems (i.e., Dmrt genes) and propose the microcrustacean Daphnia (clade Branchiopoda) as a model to study the transition from ESD to GSD.

In vitro cellular reprogramming to model gonad development and its disorders

During embryonic development, mutually antagonistic signaling cascades determine gonadal fate toward a testicular or ovarian identity. Errors in this process result in disorders of sex development (DSDs), characterized by discordance between chromosomal, gonadal, and anatomical sex. The absence of an appropriate, accessible in vitro system is a major obstacle in understanding mechanisms of sex-determination/DSDs. Here, we describe protocols for differentiation of mouse and human pluripotent cells toward gonadal progenitors. Transcriptomic analysis reveals that the in vitro-derived murine gonadal cells are equivalent to embryonic day 11.5 in vivo progenitors. Using similar conditions, Sertoli-like cells derived from 46,XY human induced pluripotent stem cells (hiPSCs) exhibit sustained expression of testis-specific genes, secrete anti-Müllerian hormone, migrate, and form tubular structures. Cells derived from 46,XY DSD female hiPSCs, carrying an NR5A1 variant, show aberrant gene expression and absence of tubule formation. CRISPR-Cas9-mediated variant correction rescued the phenotype. This is a robust tool to understand mechanisms of sex determination and model DSDs.

Metzincin metalloproteases in PGC migration and gonadal sex conversion

Development of a functional gonad includes migration of primordial germ cells (PGCs), differentiations of somatic and germ cells, formation of primary follicles or spermatogenic cysts with somatic gonadal cells, development and maturation of gametes, and subsequent releasing of mature germ cells. These processes require extensive cellular and tissue remodeling, as well as broad alterations of the surrounding extracellular matrix (ECM). Metalloproteases, including MMPs (matrix metalloproteases), ADAMs (a disintegrin and metalloproteinases), and ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs), are suggested to have critical roles in the remodeling of the ECM during gonad development. However, few research articles and reviews are available on the functions and mechanisms of metalloproteases in remodeling gonadal ECM, gonadal development, or gonadal differentiation. Moreover, most studies focused on the roles of transcription and growth factors in early gonad development and primary sex determination, leaving a significant knowledge gap on how differentially expressed metalloproteases exert effects on the ECM, cell migration, development, and survival of germ cells during the development and differentiation of ovaries or testes. We will review gonad development with focus on the evidence of metalloprotease involvements, and with an emphasis on zebrafish as a model for studying gonadal sex differentiation and metalloprotease functions.

Impact of endocrine disrupting chemicals and pharmaceuticals on Sertoli cell development and functions

Sertoli cells play essential roles in male reproduction, from supporting fetal testis development to nurturing male germ cells from fetal life to adulthood. Dysregulating Sertoli cell functions can have lifelong adverse effects by jeopardizing early processes such as testis organogenesis, and long-lasting processes such as spermatogenesis. Exposure to endocrine disrupting chemicals (EDCs) is recognized as contributing to the rising incidence of male reproductive disorders and decreasing sperm counts and quality in humans. Some drugs also act as endocrine disruptors by exerting off-target effects on endocrine tissues. However, the mechanisms of toxicity of these compounds on male reproduction at doses compatible with human exposure are still not fully resolved, especially in the case of mixtures, which remain understudied. This review presents first an overview of the mechanisms regulating Sertoli cell development, maintenance, and functions, and then surveys what is known on the impact of EDCs and drugs on immature Sertoli cells, including individual compounds and mixtures, and pinpointing at knowledge gaps. Performing more studies on the impact of mixtures of EDCs and drugs at all ages is crucial to fully understand the adverse outcomes these chemicals may induce on the reproductive system.

Turner Syndrome Mosaicism 45,X/46,XY with Genital Ambiguity and Duchenne Muscular Dystrophy: Translational Approach of a Rare Italian Case

Turner syndrome (gonadal dysgenesis with short stature and sterility) is characterized by chromosomal karyotype 45,X in 50% of cases or by mosaicism (45,X/46,XX and 45,X/46,XY) in 30-40% or X structural defects (deletions, long arm isochromosome, ring chromosome). When mosaic Turner syndrome (TS) occurs with a Y chromosome, there may be ambiguous genitalia. Duchenne muscular dystrophy (DMD) is an inherited neuromuscular disease with an X-Linked recessive pattern of inheritance that predominantly affects males, while females are usually asymptomatic. DMD has also been observed in groups of females affected by TS, not homozygous for the mutation. Here, we report a case of an Indian neonate born with ambiguous genitalia diagnosed prenatally by ultrasound who had a karyotype of 45,X/46,XY and who also had Duchenne muscular dystrophy caused by a de novo mutation in the DMD gene. Physical examination was normal without the typical dysmorphic features of TS with the exception of the genitourinary system showing ambiguous genitalia. Gender was assigned as female. At the age of three years, she had increasing difficulty walking, running, jumping and climbing stairs, proximal upper and lower extremity muscle weakness and a positive Gowers' sign. In addition, the serum creatine kinase (CK) value was over 30X the upper limit of normal. This study shows that DMD can occur in females with TS having 45,X/46,XY mosaicism and that this coexistence should be considered in women affected by TS who start to develop potential typical symptoms such as motor or developmental delay.

Fadrozole-mediated sex reversal in the embryonic chicken gonad involves a PAX2 positive undifferentiated supporting cell state

Gonadal sex differentiation among vertebrates involves divergent fates of a common group of progenitor cells present in both presumptive ovaries and testes. The first cell type to differentiate gives rise to pre-Sertoli cells in the testis, and pre-follicular cells in the ovary. These cells derive from a common lineage of so-called “supporting cells”. In birds and other egg-laying vertebrates, locally synthesised estrogen has a central role in ovarian development and influences the fate of these supporting cells. Manipulation of estrogen levels during embryonic development induces gonadal sex reversal, providing an experimental setting to evaluate the process of gonadal sex differentiation. Recently, we identified PAX2 as a novel marker of the undifferentiated supporting cell lineage in the chicken embryo, expressed in both sexes prior to overt gonadal sex differentiation. PAX2 expression is downregulated at the onset of gonadal sex differentiation in both males and females. The analysis of this undifferentiated supporting cell marker, together with Sertoli (male) and pre-granulosa (female) will enhance our understanding of supporting cell differentiation. Here we characterized the supporting cells differentiation process and identified undifferentiated supporting cells in estrogen-mediated sex reversal experiments. Female embryos treated with the aromatase inhibitor fadrozole developed into ovotestis, containing pre-granulosa cells, Sertoli cells and PAX2 positive undifferentiated supporting cells. In contrast, male embryos treated with 17β-estradiol showed no PAX2+ undifferentiated gonadal supporting cells. Fadrozole time-course as well as multiple dose analysis suggests that supporting cell transdifferentiation involves a dedifferentiation event into a PAX2+ undifferentiated supporting cell state, followed by a redifferentiation towards the opposite sex lineage.

Perivascular cells support folliculogenesis in the developing ovary

Supporting cells of the ovary, termed granulosa cells, are essential for ovarian differentiation and oogenesis by providing a nurturing environment for oocyte maintenance and maturation. Granulosa cells are specified in the fetal and perinatal ovary, and sufficient numbers of granulosa cells are critical for the establishment of follicles and the oocyte reserve. Identifying the cellular source from which granulosa cells and their progenitors are derived is an integral part of efforts to understand basic ovarian biology and the etiology of female infertility. In particular, the contribution of mesenchymal cells, especially perivascular cells, to ovarian development is poorly understood but is likely to be a source of new information regarding ovarian function. Here we have identified a cell population in the fetal ovary, which is a Nestin-expressing perivascular cell type. Using lineage tracing and ex vivo organ culture methods, we determined that perivascular cells are multipotent progenitors that contribute to granulosa, thecal, and pericyte cell lineages in the ovary. Maintenance of these progenitors is dependent on ovarian vasculature, likely reliant on endothelial-mesenchymal Notch signaling interactions. Depletion of Nestin+ progenitors resulted in a disruption of granulosa cell specification and in an increased number of germ cell cysts that fail to break down, leading to polyovular ovarian follicles. These findings highlight a cell population in the ovary and uncover a key role for vasculature in ovarian differentiation, which may lead to insights into the origins of female gonad dysgenesis and infertility.

Molecular Evolution and Inheritance Pattern of Sox Gene Family among Bovidae

Sox genes are an evolutionarily conserved family of transcription factors that play important roles in cellular differentiation and numerous complex developmental processes. In vertebrates, Sox proteins are required for cell fate decisions, morphogenesis, and the control of self-renewal in embryonic and adult stem cells. The Sox gene family has been well-studied in multiple species including humans but there has been scanty or no research into Bovidae. In this study, we conducted a detailed evolutionary analysis of this gene family in Bovidae, including their physicochemical properties, biological functions, and patterns of inheritance. We performed a genome-wide cataloguing procedure to explore the Sox gene family using multiple bioinformatics tools. Our analysis revealed a significant inheritance pattern including conserved motifs that are critical to the ability of Sox proteins to interact with the regulatory regions of target genes and orchestrate multiple developmental and physiological processes. Importantly, we report an important conserved motif, EFDQYL/ELDQYL, found in the SoxE and SoxF groups but not in other Sox groups. Further analysis revealed that this motif sequence accounts for the binding and transactivation potential of Sox proteins. The degree of protein–protein interaction showed significant interactions among Sox genes and related genes implicated in embryonic development and the regulation of cell differentiation. We conclude that the Sox gene family uniquely evolved in Bovidae, with a few exhibiting important motifs that drive several developmental and physiological processes.

A New Understanding, Guided by Single-Cell Sequencing, of the Establishment and Maintenance of the Ovarian Reserve in Mammals

BACKGROUND

Oocytes are a finite and non-renewable resource that are maintained in primordial follicle structures. The ovarian reserve is the totality of primordial follicles, present from birth, within the ovary and its establishment, size, and maintenance dictates the duration of the female reproductive lifespan. Understanding the cellular and molecular dynamics relevant to the establishment and maintenance of the reserve provides the first steps necessary for modulating both individual human and animal reproductive health as well as population dynamics.

SUMMARY

This review details the key stages of establishment and maintenance of the ovarian reserve, encompassing germ cell nest formation, germ cell nest breakdown, and primordial follicle formation and activation. Furthermore, we spotlight several formative single-cell sequencing studies that have significantly advanced our knowledge of novel molecular regulators of the ovarian reserve, which may improve our ability to modulate female reproductive lifespans.

KEY MESSAGES

The application of single-cell sequencing to studies of ovarian development in mammals, especially when leveraging genetic and environmental models, offers significant insights into fertility and its regulation. Moreover, comparative studies looking at key stages in the development of the ovarian reserve across species has the potential to impact not just human fertility, but also conservation biology, invasive species management, and agriculture.

Somatic cell fate maintenance in mouse fetal testes via autocrine/paracrine action of AMH and activin B

Fate determination and maintenance of fetal testes in most mammals occur cell autonomously as a result of the action of key transcription factors in Sertoli cells. However, the cases of freemartin, where an XX twin develops testis structures under the influence of an XY twin, imply that hormonal factor(s) from the XY embryo contribute to sex reversal of the XX twin. Here we show that in mouse XY embryos, Sertoli cell-derived anti-Mullerian hormone (AMH) and activin B together maintain Sertoli cell identity. Sertoli cells in the gonadal poles of XY embryos lacking both AMH and activin B transdifferentiate into their female counterpart granulosa cells, leading to ovotestis formation. The ovotestes remain to adulthood and produce both sperm and oocytes, although there are few of the former and the latter fail to mature. Finally, the ability of XY mice to masculinize ovaries is lost in the absence of these two factors. These results provide insight into fate maintenance of fetal testes through the action of putative freemartin factors.

Testicular Sertoli Cell Hormones in Differences in Sex Development

The Sertoli cells of the testes play an essential role during gonadal development, in addition to supporting subsequent germ cell survival and spermatogenesis. Anti-Müllerian hormone (AMH) is a member of the TGF-β superfamily, which is secreted by immature Sertoli cells from the 8th week of fetal gestation. lnhibin B is a glycoprotein, which is produced by the Sertoli cells from early in fetal development. In people with a Difference or Disorder of Sex Development (DSD), these hormones may be useful to determine the presence of testicular tissue and potential for spermatogenesis. However, fetal Sertoli cell development and function is often dysregulated in DSD conditions and altered production of Sertoli cell hormones may be detected throughout the life course in these individuals. As such this review will consider the role of AMH and inhibin B in individuals with DSD.

The changing landscape of immune cells in the fetal mouse testis

Fetal testis growth involves cell influx and extensive remodeling. Immediately after sex determination in mouse, macrophages enable normal cord formation and removal of inappropriately positioned cells. This study provides new information about macrophages and other immune cells after cord formation in fetal testes, including their density, distribution, and close cellular contacts. C57BL6J mouse testes from embryonic day (E) 13.5 to birth (post-natal day 0; PND0), were examined using immunofluorescence, immunohistochemistry, and RT-qPCR to identify macrophages (F4/80, CD206, MHCII), T cells (CD3), granulocytes/neutrophils (Ly6G), and germ cells (DDX4). F4/80⁺ cells were the most abundant, comprising 90% of CD45⁺ cells at E13.5 and declining to 65% at PND0. Changes in size, shape, and markers (CD206 and MHCII) documented during this interval align with the understanding that F4/80⁺ cells have different origins during embryonic life. CD3⁺ cells and F4/80⁻/MHCII⁺ were absent to rare until PND0. Ly6G⁺ cells were scarce at E13.5 but increased robustly by PND0 to represent half of the CD45⁺ cells. These immunofluorescence data were in accord with transcript analysis, which showed that immune marker mRNAs increased with testis age. F4/80⁺ and Ly6G⁺ cells were frequently inside cords adjacent to germ cells at E13.5 and E15.5. F4/80⁺ cells were often in clusters next to other immune cells. Macrophages inside cords at E13.5 and E15.5 (F4/80^Hi/CD206⁺) were different from macrophages at PND0 (F4/80^Dim/CD206⁻), indicating that they have distinct origins. This histological quantification coupled with transcript information identifies new cellular interactions for immune cells in fetal testis morphogenesis, and highlights new avenues for studies of their functional significance.

Isolation, culture, and characterisation of bovine ovarian fetal fibroblasts and gonadal ridge epithelial-like cells and comparison to their adult counterparts

During ovarian development, gonadal ridge epithelial-like (GREL) cells arise from the epithelial cells of the ventral surface of the mesonephros. They ultimately develop into follicular granulosa cells or into ovarian surface epithelial cells. Stromal fibroblasts arise from the mesonephros and penetrate the ovary. We developed methods for isolating and culturing fetal ovarian GREL cells and ovarian fibroblasts by expansion of colonies without passage. In culture, these two cell types were morphologically different. We examined the expression profile of 34 genes by qRT-PCR, of which 24 genes had previously been studied in whole fetal ovaries. Expression of nine of the 10 newly-examined genes in fetal ovaries correlated with gestational age (MUC1, PKP2, CCNE1 and CCNE2 negatively; STAR, COL4A1, GJA1, LAMB2 and HSD17B1 positively). Comparison between GREL cells and fetal fibroblasts revealed higher expression of KRT19, PKP2, OCLN, MUC1, ESR1 and LGR5 and lower expression of GJA1, FOXL2, NR2F2, FBN1, COL1A1, NR5A1, CCND2, CCNE1 and ALDH1A1. Expression of CCND2, CCNE1, CCNE2, ESR2 and TGFBR1 was higher in the fetal fibroblasts than in adult fibroblasts; FBN1 was lower. Expression of OCLN, MUC1, LAMB2, NR5A1, ESR1, ESR2, and TGFBR3 was lower in GREL cells than ovarian surface epithelial cells. Expression of KRT19, DSG2, PKP2, OCLN, MUC1, FBN1, COL1A1, COL3A1, STAR and TGFBR2 was higher and GJA1, CTNNB1, LAMB2, NR5A1, CYP11A1, HSD3B1, CYP19A1, HSD17B1, FOXL2, ESR1, ESR2, TGFBR3 and CCND2 was lower in GREL cells compared to granulosa cells. TGFβ1 altered the expression of COL1A1, COL3A1 and FBN1 in fetal fibroblasts and epidermal growth factor altered the expression of FBN1 and COL1A1. In summary, the two major somatic cell types of the developing ovary have distinct gene expression profiles. They, especially GREL cells, also differ from the cells they ultimately differentiate in to. The regulation of cell fate determination, particularly of the bi-potential GREL cells, remains to be elucidated.

Case Report: Disorder of Sexual Development in a Chinese Crested Dog With XX/XY Leukocyte Chimerism and Mixed Cell Testicular Tumors

A 10-year-old intact female Chinese Crested dog was presented for evaluation and further diagnostics due to persistent symptoms of vulvar swelling, vaginal discharge, and an 8-year history of acyclicity. At presentation, generalized hyperpigmentation and truncal alopecia were identified, with no aberrations of the female phenotype. Vaginal cytology confirmed the influence of estrogen at multiple veterinary visits, and hormonal screening of progesterone and anti-Mullerian hormone indicated gonadal presence. Based on findings from abdominal laparotomy and gonadectomy, the tissue was submitted for histopathology. Histopathologic evaluation identified the gonads to be abnormal testes containing multiple Sertoli and interstitial (Leydig) cell tumors. The histopathologic diagnosis of testes and concurrent normal external female phenotype in the patient lead to a diagnosis of a disorder of sexual development (DSD). Karyotype evaluation by conventional and molecular analysis revealed a two cell line chimeric pattern of 78,XX (80%) and 78,XY (20%) among blood leukocytes, as well as a positive PCR test for the Y-linked SRY gene. Cytogenetic analysis of skin fibroblasts revealed the presence of 78,XX cells exclusively, and PCR tests for the Y-linked SRY gene were negative in the hair and skin samples. These results are consistent with an XX/XY blood chimerism. This is one of the few case reports of a canine with the diagnosis of leukocyte chimerism with normal female phenotypic external genitalia. This case illustrates a distinct presentation for hormonally active Sertoli cell tumorigenesis and demonstrates surgery as a curative treatment option for clinically affected patients.

Deciphering Sex-Specific Differentiation of Human Fetal Gonads: Insight From Experimental Models

Sex-specific gonadal differentiation is initiated by the expression of SRY in male foetuses. This promotes a signalling pathway directing testicular development, while in female foetuses the absence of SRY and expression of pro-ovarian factors promote ovarian development. Importantly, in addition to the initiation of a sex-specific signalling cascade the opposite pathway is simultaneously inhibited. The somatic cell populations within the gonads dictates this differentiation as well as the development of secondary sex characteristics via secretion of endocrine factors and steroid hormones. Opposing pathways SOX9/FGF9 (testis) and WNT4/RSPO1 (ovary) controls the development and differentiation of the bipotential mouse gonad and even though sex-specific gonadal differentiation is largely considered to be conserved between mice and humans, recent studies have identified several differences. Hence, the signalling pathways promoting early mouse gonad differentiation cannot be directly transferred to human development thus highlighting the importance of also examining this signalling in human fetal gonads. This review focus on the current understanding of regulatory mechanisms governing human gonadal sex differentiation by combining knowledge of these processes from studies in mice, information from patients with differences of sex development and insight from manipulation of selected signalling pathways in ex vivo culture models of human fetal gonads.

Impact of in Utero Rat Exposure to 17Alpha-Ethinylestradiol or Genistein on Testicular Development and Germ Cell Gene Expression

Although the decline in male fertility is believed to partially result from environmental exposures to xenoestrogens during critical developmental windows, the underlying mechanisms are still poorly understood. Experimental in utero exposures in rodents have demonstrated the negative impact of xenoestrogens on reproductive development, long-term adult reproductive function and offspring health. In addition, transcriptomic studies have demonstrated immediate effects on gene expression in fetal reproductive tissues, However, the immediate molecular effects on the developing germ cells have been poorly investigated. Here, we took advantage of a transgenic rat expressing the green fluorescent protein specifically in germ cells allowing purification of perinatal GFP-positive germ cells. Timed-pregnant rats were exposed to ethinylestradiol (EE2, 2 μg/kg/d), genistein (GE, 10 mg/kg/d) or vehicle by gavage, from gestational days (GD) 13–19; testes were sampled at GD20 or post-natal (PND) 5 for histological analysis and sorting of GFP-positive cells. While EE2-exposed females gained less weight during treatment compared to controls, neither treatment affected the number of pups per litter, sex ratio, anogenital distance, or body and gonadal weights of the offspring. Although GE significantly decreased circulating testosterone at GD20, no change was observed in either testicular histology or germ cell and sertoli cell densities. Gene expression was assessed in GFP-positive cells using Affymetrix Rat Gene 2.0 ST microarrays. Analysis of differentially expressed genes (DEGs) (p < 0.05; fold change 1.5) identified expression changes of 149 and 128 transcripts by EE2 and GE respectively at GD20, and 287 and 207 transcripts at PND5, revealing an increased effect after the end of treatment. Only about 1% of DEGs were common to both stages for each treatment. Functional analysis of coding DEG revealed an overrepresentation of olfactory transduction in all groups. In parallel, many non-coding RNAs were affected by both treatments, the most represented being small nucleolar and small nuclear RNAs. Our data suggest that despite no immediate toxic effects, fetal exposure to xenoestrogens can induce subtle immediate changes in germ cell gene expression. Moreover, the increased number of DEGs between GD20 and PND5 suggests an effect of early exposures with latent impact on later germ cell differentiation.

Small-Molecule-Driven Direct Reprogramming of Fibroblasts into Functional Sertoli-Like Cells as a Model for Male Reproductive Toxicology

Sertoli cells (SCs) are vital to providing morphological and nutritional support for spermatogenesis. Defects in SCs often lead to infertility. SCs transplantation is a promising potential strategy to compensate for SC dysfunction. However, isolation of SCs from testes is impractical due to obvious and ethical limitations. Here, a molecular cocktail is identified comprising of pan-BET family inhibitor (I-BET151), retinoic acid, and riluzole that enables the efficient conversion of fibroblasts into functional Sertoli-like cells (CiSCs). The gene expression profiles of CiSCs resemble those of mature SCs and exhibit functional properties such as the formation of testicular seminiferous tubules, engulfment of apoptotic sperms, supporting the survival of germ cells, and suppressing proliferation of primary lymphocytes in vitro. Moreover, CiSCs are sensitive to toxic substances, making them an alternative model to study the deleterious effects of toxicants on SCs. The study provides an efficient approach to reprogram fibroblasts into functional SCs by using pure chemical compounds.

Tle4z1 Facilitate the Male Sexual Differentiation of Chicken Embryos

Background

Sex differentiation is a complex and precisely regulated process by multiple genes in chicken. However, it is still unclear on the key genes of sex differentiation.

Objective

To explore the function of Tle4z1 screened by RNA-seq sequencing on sex differentiation during the development of chicken embryos.

Methods

Tle4z1 was differentially expressed from the RNA-seq of ESCs and PGCs in male and female chickens. Then, we established an effective method to overexpression or knocking down the expression of Tle4z1 in ovo and in vitro, respectively. Histomorphological observation, qRT-PCR and ELISA were applied to detect the function of Tle4z1 in the process of male sex differentiation by injecting vectors into embryos at day 0.

Results

It showed that Tle4z1 has significant male preference in embryonic day 4.5, such phenomenon persisted during the growth period of chicken embryos. Morphological observation results showed that the gonads on both sides of genetic male (ZZ) embryos with Tle4z1 knocking down developed asymmetrically, the gonadal cortex became thicker showing the typical characteristics of genetic female (ZW) gonads. Furthermore, the expression of Cyp19a1, which dominates female differentiation, was significantly increased, while the expression of male marker genes Dmrt1, Sox9, WT1 and AR was significantly downregulated. In addition, the concentration of testosterone also significantly decreased, which was positively correlated with the expression of Tle4z1 (P < 0.01). Conversely, the ZW embryo showed defeminized development when Tle4z1 was overexpressed.

Conclusion

We prove that the Tle4z1 is a novel gene through the male sexual differentiation via gene regulation process and synthesis of testosterone, which construct the basis for understanding the molecular mechanism of sex differentiation in chickens.

Ameliorative effect of N-acetylcysteine on the testicular tissue of adult male albino rats after glyphosate-based herbicide exposure

Glyphosate (GLP) is a broad-spectrum herbicide that is frequently used in crop production, but its residues remain in foodstuffs. This, in turn, has led to potential adverse effects on both human and animal health. Recent studies emphasized that GLP induces teratogenic effects and reproductive disorders, but its mechanism of toxicity is highly debated. N-acetylcysteine (NAC) is well known for its potent antioxidant capacity in addition to anti-inflammatory and cytoprotective properties. Therefore, our study aimed to investigate the reproductive toxicity of GLP in mature rats and evaluate the possible ameliorative effect of NAC against this toxicity. To this end, 30 adult male rats were assigned into three groups (10 rats per group) as follows: Group I, negative control; group II, GLP-exposed; 375 mg/kg GLP, orally; group III, NAC-cotreated, 160 mg/kg NAC 1 h before GLP, plus GLP, 375 mg/kg orally for 6 weeks. At the end of the experiment, the testicles were collected for semen analysis and biochemical, histopathological, and immunohistochemical studies. GLP-exposed rats exhibited disturbances in seminal parameters and a significant increase in malondialdehyde levels and expression of apoptotic markers. Several histopathological changes were observed, including strong immunoreactions for caspase-3 and proliferating cell nuclear antigen. Conversely, the administration of NAC before GLP was able to improve seminal parameters, attenuate the induced oxidative stress and apoptosis in addition to the regeneration of testicular damage. In conclusion, NAC can ameliorate the reproductive toxicity induced by GLP to an acceptable degree.

Dissecting Human Gonadal Cell Lineage Specification and Sex Determination Using A Single-cell RNA-seq Approach

Gonadal somatic cells are the main players in gonad development and are important for sex determination and germ cell development. Here, using a time-series single-cell RNA sequencing (scRNA-seq) strategy, we analyzed fetal germ cells (FGCs) and gonadal somatic cells in human embryos and fetuses. Clustering analysis of testes and ovaries revealed several novel cell subsets, including POU5F1⁺SPARC⁺ FGCs and KRT19⁺ somatic cells. Furthermore, our data indicated that the bone morphogenetic protein (BMP) signaling pathway plays cell type-specific and developmental stage-specific roles in testis development and promotes the gonocyte-to-spermatogonium transition (GST) in late-stage testicular mitotic arrest FGCs. Intriguingly, testosterone synthesis function transitioned from fetal Sertoli cells to adult Leydig cells in a stepwise manner. In our study, potential interactions between gonadal somatic cells were systematically explored and we identified cell type-specific developmental defects in both FGCs and gonadal somatic cells in a Turner syndrome embryo (45, XO). Our work provides a blueprint of the complex yet highly ordered development of and the interactions among human FGCs and gonadal somatic cells.

Associations between testicular development and fetal size in the pig

Background

Impaired reproductive performance is the largest contributing factor for the removal of boars from commercial systems. Intrauterine growth restricted piglets represent 25% of the total number of piglets born and have impaired reproductive performance. This study aimed to improve the understanding of temporal changes in testicular gene expression during testes development in fetuses of different size. The lightest and closest to mean litter weight (CTMLW) male Large White × Landrace littermates were collected at gestational days (GD) 45, 60 and 90 (n = 5–6 litters/GD).

Results

Testes weight and testes weight as a percentage of fetal weight were not associated with fetal size at GD60 or 90. Fetal plasma testosterone was not associated with fetal size at GD90. There was no association between fetal size and seminiferous tubule area and number, number of germ or Sertoli cells per tubule. The lightest fetuses tended to have wider seminiferous tubules compared to the CTMLW fetuses at GD90 (P = 0.077). The testicular expression of KI67 (P ≤ 0.01) and BAX:BCL2 ratio (P = 0.058) mRNAs decreased as gestation progressed. Greater SPP1 mRNA expression was observed at GD60 when compared with GD45 and 90 (P ≤ 0.05). Lower expression of DMRT1 and SPP1 (P < 0.01) mRNAs was observed in testes associated with the lightest fetuses compared to the CTMLW fetuses at GD90.

Conclusions

These findings provide novel insights into the expression profiles of genes associated with testicular development and function. Further, these data suggest that programming of reproductive potential in IUGR boars occurs late in gestation, providing a platform for further mechanistic investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00678-3.

CBX2 in DSD: The Quirky Kid on the Block

Sex development is an intricate and crucial process in all vertebrates that ensures the continued propagation of genetic diversity within a species, and ultimately their survival. Perturbations in this process can manifest as disorders/differences of sex development (DSD). Various transcriptional networks have been linked to development of the gonad into either male or female, which is actively driven by a set of genes that function in a juxtaposed manner and is maintained through the developmental stages to preserve the final sexual identity. One such identified gene is Chromobox homolog 2 (CBX2), an important ortholog of the Polycomb group (PcG) proteins, that functions as both chromatin modifier and highly dynamic transactivator. CBX2 was shown to be an essential factor for gonadal development in mammals, as genetic variants or loss-of-function of CBX2 can cause sex reversal in mice and humans. Here we will provide an overview of CBX2, its biological functions at molecular level, and the CBX2-dependent transcriptional landscape in gonadal development and DSD.

Genetic, Molecular, and Cellular Determinants of Sex-Specific Cardiovascular Traits

Despite the well-known sex dimorphism in cardiovascular disease traits, the exact genetic, molecular, and cellular underpinnings of these differences are not well understood. A growing body of evidence currently points at the links between cardiovascular disease traits and the genome, epigenome, transcriptome, and metabolome. However, the sex-specific differences in these links remain largely unstudied due to challenges in bioinformatic methods, inadequate statistical power, analytic costs, and paucity of valid experimental models. This review article provides an overview of the literature on sex differences in genetic architecture, heritability, epigenetic changes, transcriptomic signatures, and metabolomic profiles in relation to cardiovascular disease traits. We also review the literature on the associations between sex hormones and cardiovascular disease traits and discuss the potential mechanisms underlying these associations, focusing on human studies.

Structural brain differences do not mediate the relations between sex and personality or psychopathology

INTRODUCTION

Males and females tend to exhibit small but reliable differences in personality traits and indices of psychopathology that are relatively stable over time and across cultures. Previous work suggests that sex differences in brain structure account for differences in domains of cognition.

METHODS

We used data from the Human Connectome Project (N = 1098) to test whether sex differences in brain morphometry account for observed differences in the personality traits neuroticism and agreeableness, as well as symptoms of internalizing and externalizing psychopathology. We operationalized brain morphometry in three ways: omnibus measures (e.g., total gray matter volume), Glasser regions defined through a multi-modal parcellation approach, and Desikan regions defined by structural features of the brain.

RESULTS

Most expected sex differences in personality, psychopathology, and brain morphometry were observed, but the statistical mediation analyses were null: sex differences in brain morphometry did not account for sex differences in personality or psychopathology.

CONCLUSIONS

Men and women tend to exhibit meaningful differences in personality and psychopathology, as well as in omnibus morphometry and regional morphometric differences as defined by the Glasser and Desikan atlases, but these morphometric differences appear unrelated to the psychological differences.

OUP accepted manuscript

The pathways of gametogenesis encompass elaborate cellular specialization accompanied by precise partitioning of the genome content in order to produce fully matured spermatozoa and oocytes. Transcription factors are an important class of molecules that function in gametogenesis to regulate intrinsic gene expression programs, play essential roles in specifying (or determining) germ cell fate and assist in guiding full maturation of germ cells and maintenance of their populations. Moreover, in order to reinforce or redirect cell fate in vitro, it is transcription factors that are most frequently induced, over-expressed or activated. Many reviews have focused on the molecular development and genetics of gametogenesis, in vivo and in vitro, in model organisms and in humans, including several recent comprehensive reviews: here, we focus specifically on the role of transcription factors. Recent advances in stem cell biology and multi-omic studies have enabled deeper investigation into the unique transcriptional mechanisms of human reproductive development. Moreover, as methods continually improve, in vitro differentiation of germ cells can provide the platform for robust gain- and loss-of-function genetic analyses. These analyses are delineating unique and shared human germ cell transcriptional network components that, together with somatic lineage specifiers and pluripotency transcription factors, function in transitions from pluripotent stem cells to gametes. This grand theme review offers additional insight into human infertility and reproductive disorders that are linked predominantly to defects in the transcription factor networks and thus may potentially contribute to the development of novel treatments for infertility.

Fetal Estrogens are not Involved in Sex Determination But Critical for Early Ovarian Differentiation in Rabbits

AROMATASE is encoded by the CYP19A1 gene and is the cytochrome enzyme responsible for estrogen synthesis in vertebrates. In most mammals, a peak of CYP19A1 gene expression occurs in the fetal XX gonad when sexual differentiation is initiated. To elucidate the role of this peak, we produced 3 lines of TALEN genetically edited CYP19A1 knockout (KO) rabbits that were devoid of any estradiol production. All the KO XX rabbits developed as females with aberrantly small ovaries in adulthood, an almost empty reserve of primordial follicles, and very few large antrum follicles. Ovulation never occurred. Our histological, immunohistological, and transcriptomic analyses showed that the estradiol surge in the XX fetal rabbit gonad is not essential to its determination as an ovary, or for meiosis. However, it is mandatory for the high proliferation and differentiation of both somatic and germ cells, and consequently for establishment of the ovarian reserve.

Activin A and Sertoli Cells: Key to Fetal Testis Steroidogenesis

The long-standing knowledge that Sertoli cells determine fetal testosterone production levels is not widespread, despite being first reported over a decade ago in studies of mice. Hence any ongoing use of testosterone as a marker of Leydig cell function in fetal testes is inappropriate. By interrogating new scRNAseq data from human fetal testes, we demonstrate this situation is also likely to be true in humans. This has implications for understanding how disruptions to either or both Leydig and Sertoli cells during the in utero masculinization programming window may contribute to the increasing incidence of hypospadias, cryptorchidism, testicular germ cell tumours and adult infertility. We recently discovered that activin A levels directly govern androgen production in mouse Sertoli cells, because the enzymes that drive the conversion of the precursor androgen androstenedione to generate testosterone are produced exclusively in Sertoli cells in response to activin A. This minireview addresses the implications of this growing understanding of how in utero exposures affect fetal masculinization for future research on reproductive health, including during programming windows that may ultimately be relevant for organ development in males and females.

Trapped in the Wrong Body? Transgender Identity Claims, Body-Self Dualism, and the False Promise of Gender Reassignment Therapy

In this article, I explore difficult and sensitive questions regarding the nature of transgender identity claims and the appropriate medical treatment for those suffering from gender dysphoria. I first analyze conceptions of transgender identity, highlighting the prominence of the wrong-body narrative and its dualist presuppositions. I then briefly argue that dualism is false because our bodily identity (including our body's biological organization for sexual reproduction as male or female) is essential and intrinsic to our overall personal identity and explain why a sound, nondualist anthropology implies that gender identity cannot be entirely divorced from sexual identity. Finally, I make the case that arguments in favor of hormonal and surgical treatments for gender dysphoria rest on this mistaken dualist anthropology, and that these treatments therefore give false hope to those suffering from gender dysphoria, while causing irreversible bodily harm and diverting attention from underlying psychological problems that often need to be addressed. I also briefly discuss how these philosophical claims relate to empirical studies on the outcomes of hormonal and surgical treatments for gender dysphoria and to testimonies of transgender individuals who regret having undergone these treatments.

Modest sexual size dimorphism and allometric growth: a study based on growth and gonad development in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae)

Sexual size dimorphism (SSD) is a notable phenomenon in terrestrial animals, and it is correlated with unusual morphological traits. To date, the underlying sex-specific growth strategies throughout the ontogenetic stage of spiders are poorly understood. Here, we comprehensively investigated how the growth trajectories and gonad development shaped SSD in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae). We also hypothesized the potential growth allometry among the carapace, abdomen, and gonads of spiders in both sexes. By measuring the size of the carapace and abdomen, investigating developmental duration and growth rate, describing the gonadal sections, and calculating the area of gonads at all instars from hatching to maturity, we demonstrated that SSD results from sex-specific growth strategies. Our results indicated that the growth and developmental differences between both sexes appeared at early life stages, and there was allometric growth in the carapace, abdomen, and gonads between males and females.

A duplicated copy of id2b is an unusual sex-determining candidate gene on the Y chromosome of arapaima (Arapaima gigas)

Arapaima gigas is one of the largest freshwater fish species of high ecological and economic importance. Overfishing and habitat destruction are severe threats to the remaining wild populations. By incorporating a chromosomal Hi-C contact map, we improved the arapaima genome assembly to chromosome-level, revealing an unexpected high degree of chromosome rearrangements during evolution of the bonytongues (Osteoglossiformes). Combining this new assembly with pool-sequencing of male and female genomes, we identified id2bbY, a duplicated copy of the inhibitor of DNA binding 2b (id2b) gene on the Y chromosome as candidate male sex-determining gene. A PCR-test for id2bbY was developed, demonstrating that this gene is a reliable male-specific marker for genotyping. Expression analyses showed that this gene is expressed in juvenile male gonads. Its paralog, id2ba, exhibits a male-biased expression in immature gonads. Transcriptome analyses and protein structure predictions confirm id2bbY as a prime candidate for the master sex-determiner. Acting through the TGFβ signaling pathway, id2bbY from arapaima would provide the first evidence for a link of this family of transcriptional regulators to sex determination. Our study broadens our current understanding about the evolution of sex determination genetic networks and provide a tool for improving arapaima aquaculture for commercial and conservation purposes.