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Physiological Reviews Jul 2021A diverse array of sex determination () mechanisms, encompassing environmental to genetic, have been found to exist among vertebrates, covering a spectrum from fixed... (Review)
Review
A diverse array of sex determination () mechanisms, encompassing environmental to genetic, have been found to exist among vertebrates, covering a spectrum from fixed mechanisms (mammals) to functional sex change in fishes (sequential hermaphroditic fishes). A major landmark in vertebrate was the discovery of the gene in 1990. Since that time, many attempts to clone an ortholog from nonmammalian vertebrates remained unsuccessful, until 2002, when was discovered as the gene of a small fish, medaka. Surprisingly, however, was found in only 2 species among more than 20 species of medaka, suggesting a large diversity of genes among vertebrates. Considerable progress has been made over the last 3 decades, such that it is now possible to formulate reasonable paradigms of how and gonadal sex differentiation may work in some model vertebrate species. This review outlines our current understanding of vertebrate and gonadal sex differentiation, with a focus on the molecular and cellular mechanisms involved. An impressive number of genes and factors have been discovered that play important roles in testicular and ovarian differentiation. An antagonism between the male and female pathway genes exists in gonads during both sex differentiation and, surprisingly, even as adults, suggesting that, in addition to sex-changing fishes, gonochoristic vertebrates including mice maintain some degree of gonadal sexual plasticity into adulthood. Importantly, a review of various mechanisms among vertebrates suggests that this is the ideal biological event that can make us understand the evolutionary conundrums underlying speciation and species diversity.
Topics: Animals; Female; Gonads; Male; Sex Determination Processes; Sex Differentiation; Vertebrates
PubMed: 33180655
DOI: 10.1152/physrev.00044.2019 -
Nature Jul 2022Gonadal development is a complex process that involves sex determination followed by divergent maturation into either testes or ovaries. Historically, limited tissue...
Gonadal development is a complex process that involves sex determination followed by divergent maturation into either testes or ovaries. Historically, limited tissue accessibility, a lack of reliable in vitro models and critical differences between humans and mice have hampered our knowledge of human gonadogenesis, despite its importance in gonadal conditions and infertility. Here, we generated a comprehensive map of first- and second-trimester human gonads using a combination of single-cell and spatial transcriptomics, chromatin accessibility assays and fluorescent microscopy. We extracted human-specific regulatory programmes that control the development of germline and somatic cell lineages by profiling equivalent developmental stages in mice. In both species, we define the somatic cell states present at the time of sex specification, including the bipotent early supporting population that, in males, upregulates the testis-determining factor SRY and sPAX8s, a gonadal lineage located at the gonadal-mesonephric interface. In females, we resolve the cellular and molecular events that give rise to the first and second waves of granulosa cells that compartmentalize the developing ovary to modulate germ cell differentiation. In males, we identify human SIGLEC15 and TREM2 fetal testicular macrophages, which signal to somatic cells outside and inside the developing testis cords, respectively. This study provides a comprehensive spatiotemporal map of human and mouse gonadal differentiation, which can guide in vitro gonadogenesis.
Topics: Animals; Cell Lineage; Chromatin; Female; Germ Cells; Granulosa Cells; Humans; Immunoglobulins; Macrophages; Male; Membrane Glycoproteins; Membrane Proteins; Mice; Microscopy, Fluorescence; Ovary; PAX8 Transcription Factor; Pregnancy; Pregnancy Trimester, First; Pregnancy Trimester, Second; Receptors, Immunologic; Sex Differentiation; Single-Cell Analysis; Testis; Transcriptome
PubMed: 35794482
DOI: 10.1038/s41586-022-04918-4 -
Endocrinology Oct 2020Gonadal hormones contribute to the sexual differentiation of brain and behavior throughout the lifespan, from initial neural patterning to "activation" of adult... (Review)
Review
Gonadal hormones contribute to the sexual differentiation of brain and behavior throughout the lifespan, from initial neural patterning to "activation" of adult circuits. Sexual behavior is an ideal system in which to investigate the mechanisms underlying hormonal activation of neural circuits. Sexual behavior is a hormonally regulated, innate social behavior found across species. Although both sexes seek out and engage in sexual behavior, the specific actions involved in mating are sexually dimorphic. Thus, the neural circuits mediating sexual motivation and behavior in males and females are overlapping yet distinct. Furthermore, sexual behavior is strongly dependent on circulating gonadal hormones in both sexes. There has been significant recent progress on elucidating how gonadal hormones modulate physiological properties within sexual behavior circuits with consequences for behavior. Therefore, in this mini-review we review the neural circuits of male and female sexual motivation and behavior, from initial sensory detection of pheromones to the extended amygdala and on to medial hypothalamic nuclei and reward systems. We also discuss how gonadal hormones impact the physiology and functioning of each node within these circuits. By better understanding the myriad of ways in which gonadal hormones impact sexual behavior circuits, we can gain a richer and more complete appreciation for the neural substrates of complex behavior.
Topics: Adult; Animals; Brain; Female; Hormones; Humans; Male; Nerve Net; Sex Characteristics; Sex Differentiation; Sexual Behavior; Sexual Behavior, Animal
PubMed: 32845294
DOI: 10.1210/endocr/bqaa150 -
Journal of Neuroendocrinology Jul 2018Sexual identity and sexual orientation are independent components of a person's sexual identity. These dimensions are most often in harmony with each other and with an... (Review)
Review
Sexual identity and sexual orientation are independent components of a person's sexual identity. These dimensions are most often in harmony with each other and with an individual's genital sex, although not always. The present review discusses the relationship of sexual identity and sexual orientation to prenatal factors that act to shape the development of the brain and the expression of sexual behaviours in animals and humans. One major influence discussed relates to organisational effects that the early hormone environment exerts on both gender identity and sexual orientation. Evidence that gender identity and sexual orientation are masculinised by prenatal exposure to testosterone and feminised in it absence is drawn from basic research in animals, correlations of biometric indices of androgen exposure and studies of clinical conditions associated with disorders in sexual development. There are, however, important exceptions to this theory that have yet to be resolved. Family and twin studies indicate that genes play a role, although no specific candidate genes have been identified. Evidence that relates to the number of older brothers implicates maternal immune responses as a contributing factor for male sexual orientation. It remains speculative how these influences might relate to each other and interact with postnatal socialisation. Nonetheless, despite the many challenges to research in this area, existing empirical evidence makes it clear that there is a significant biological contribution to the development of an individual's sexual identity and sexual orientation.
Topics: Animals; Brain; Female; Gender Identity; Humans; Male; Sex Differentiation; Sexual Partners; Sexuality
PubMed: 29211317
DOI: 10.1111/jne.12562 -
Journal of Neuroendocrinology Feb 2022Widespread sex differences in human brain structure and function have been reported. Research on animal models has demonstrated that sex differences in brain and... (Review)
Review
Widespread sex differences in human brain structure and function have been reported. Research on animal models has demonstrated that sex differences in brain and behavior are induced by steroid hormones during specific, hormone sensitive, developmental periods. It was shown that typical male neural and behavioral characteristics develop under the influence of testosterone, mostly acting during perinatal development. By contrast, typical female neural and behavioral characteristics may actually develop under the influence of estradiol during a specific prepubertal period. This review provides an overview of our current knowledge on the role of steroid hormones in the sexual differentiation of the human brain. Both clinical and neuroimaging data obtained in patients with altered androgen levels/actions (i.e., congenital adrenal hyperplasia or complete androgen insensitivity syndrome [CAIS]), point to an important role of (prenatal) androgens in inducing typical male neural and psychosexual characteristics in humans. In contrast to rodents, there appears to be no obvious role for estrogens in masculinizing the human brain. Furthermore, data from CAIS also suggest a contribution of sex chromosome genes to the development of the human brain. The final part of this review is dedicated to a brief discussion of gender incongruence, also known as gender dysphoria, which has been associated with an altered or less pronounced sexual differentiation of the brain.
Topics: Androgen-Insensitivity Syndrome; Androgens; Animals; Brain; Female; Gonadal Steroid Hormones; Humans; Male; Pregnancy; Sex Differentiation; Steroids
PubMed: 34708466
DOI: 10.1111/jne.13050 -
Single-cell transcriptome reveals insights into the development and function of the zebrafish ovary.ELife May 2022Zebrafish are an established research organism that has made many contributions to our understanding of vertebrate tissue and organ development, yet there are still...
Zebrafish are an established research organism that has made many contributions to our understanding of vertebrate tissue and organ development, yet there are still significant gaps in our understanding of the genes that regulate gonad development, sex, and reproduction. Unlike the development of many organs, such as the brain and heart that form during the first few days of development, zebrafish gonads do not begin to form until the larval stage (≥5 days post-fertilization). Thus, forward genetic screens have identified very few genes required for gonad development. In addition, bulk RNA-sequencing studies that identify genes expressed in the gonads do not have the resolution necessary to define minor cell populations that may play significant roles in the development and function of these organs. To overcome these limitations, we have used single-cell RNA sequencing to determine the transcriptomes of cells isolated from juvenile zebrafish ovaries. This resulted in the profiles of 10,658 germ cells and 14,431 somatic cells. Our germ cell data represents all developmental stages from germline stem cells to early meiotic oocytes. Our somatic cell data represents all known somatic cell types, including follicle cells, theca cells, and ovarian stromal cells. Further analysis revealed an unexpected number of cell subpopulations within these broadly defined cell types. To further define their functional significance, we determined the location of these cell subpopulations within the ovary. Finally, we used gene knockout experiments to determine the roles of and for oocyte development and sex determination and/or differentiation, respectively. Our results reveal novel insights into zebrafish ovarian development and function, and the transcriptome profiles will provide a valuable resource for future studies.
Topics: Animals; Female; Gonads; Ovary; Sex Differentiation; Transcriptome; Zebrafish
PubMed: 35588359
DOI: 10.7554/eLife.76014 -
Cellular and Molecular Life Sciences :... Dec 2021Zebrafish have emerged as a major model organism to study vertebrate reproduction due to their high fecundity and external development of eggs and embryos. The... (Review)
Review
Zebrafish have emerged as a major model organism to study vertebrate reproduction due to their high fecundity and external development of eggs and embryos. The mechanisms through which zebrafish determine their sex have come under extensive investigation, as they lack a definite sex-determining chromosome and appear to have a highly complex method of sex determination. Single-gene mutagenesis has been employed to isolate the function of genes that determine zebrafish sex and regulate sex-specific differentiation, and to explore the interactions of genes that promote female or male sexual fate. In this review, we focus on recent advances in understanding of the mechanisms, including genetic and environmental factors, governing zebrafish sex development with comparisons to gene functions in other species to highlight conserved and potentially species-specific mechanisms for specifying and maintaining sexual fate.
Topics: Animals; Female; Germ Cells; Male; Protein Processing, Post-Translational; RNA; Sex Determination Processes; Sex Differentiation; Zebrafish
PubMed: 34936027
DOI: 10.1007/s00018-021-04066-4 -
Biology of Sex Differences Jun 2022In this systematic review, we highlight the differences between the male and female zebrafish brains to understand their differentiation and their use in studying... (Review)
Review
In this systematic review, we highlight the differences between the male and female zebrafish brains to understand their differentiation and their use in studying sex-specific neurological diseases. Male and female brains display subtle differences at the cellular level which may be important in driving sex-specific signaling. Sex differences in the brain have been observed in humans as well as in non-human species. However, the molecular mechanisms of brain sex differentiation remain unclear. The classical model of brain sex differentiation suggests that the steroid hormones derived from the gonads are the primary determinants in establishing male and female neural networks. Recent studies indicate that the developing brain shows sex-specific differences in gene expression prior to gonadal hormone action. Hence, genetic differences may also be responsible for differentiating the brain into male and female types. Understanding the signaling mechanisms involved in brain sex differentiation could help further elucidate the sex-specific incidences of certain neurological diseases. The zebrafish model could be appropriate for enhancing our understanding of brain sex differentiation and the signaling involved in neurological diseases. Zebrafish brains show sex-specific differences at the hormonal level, and recent advances in RNA sequencing have highlighted critical sex-specific differences at the transcript level. The differences are also evident at the cellular and metabolite levels, which could be important in organizing sex-specific neuronal signaling. Furthermore, in addition to having one ortholog for 70% of the human gene, zebrafish also shares brain structural similarities with other higher eukaryotes, including mammals. Hence, deciphering brain sex differentiation in zebrafish will help further enhance the diagnostic and pharmacological intervention of neurological diseases.
Topics: Animals; Brain; Female; Gonads; Male; Mammals; Sex Characteristics; Sex Differentiation; Zebrafish
PubMed: 35715828
DOI: 10.1186/s13293-022-00442-2 -
Frontiers in Neuroendocrinology Jan 2019Sex plays a role in the incidence and outcome of neurological illnesses, also influencing the response to treatments. Despite sexual differentiation of the brain has... (Review)
Review
Sex plays a role in the incidence and outcome of neurological illnesses, also influencing the response to treatments. Despite sexual differentiation of the brain has been extensively investigated, the study of sex differences in microglia, the brain's resident immune cells, has been largely neglected until recently. To fulfill this gap, our laboratory developed several tools, including cellular and animal models, which bolstered in-depth studies on sexual differentiation of microglia and its impact on brain physiology, as well as on the onset and progression of neurological disorders. Here, we summarize the current status of knowledge on the sex-dependent function of microglia, and report recent evidence linking these cells to the sexual bias in the susceptibility to neurological brain diseases.
Topics: Animals; Brain; Brain Diseases; Humans; Microglia; Sex Characteristics; Sex Differentiation
PubMed: 30481522
DOI: 10.1016/j.yfrne.2018.11.003 -
International Journal of Molecular... May 2023Sex determination and differentiation are processes by which a bipotential gonad adopts either a testicular or ovarian cell fate, and secondary sexual characteristics... (Review)
Review
Sex determination and differentiation are processes by which a bipotential gonad adopts either a testicular or ovarian cell fate, and secondary sexual characteristics adopt either male or female developmental patterns. In birds, although genetic factors control the sex determination program, sex differentiation is sensitive to hormones, which can induce sex reversal when disturbed. Although these sex-reversed birds can form phenotypes opposite to their genotypes, none can experience complete sex reversal or produce offspring under natural conditions. Promising evidence indicates that the incomplete sex reversal is associated with cell autonomous sex identity (CASI) of avian cells, which is controlled by genetic factors. However, studies cannot clearly describe the regulatory mechanism of avian CASI and sex development at present, and these factors require further exploration. In spite of this, the abundant findings of avian sex research have provided theoretical bases for the progress of gender control technologies, which are being improved through interdisciplinary co-operation and will ultimately be employed in poultry production. In this review, we provide an overview of avian sex determination and differentiation and comprehensively summarize the research progress on sex reversal in birds, especially chickens. Importantly, we describe key issues faced by applying gender control systems in poultry production and chronologically summarize the development of avian sex control methods. In conclusion, this review provides unique perspectives for avian sex studies and helps scientists develop more advanced systems for sex regulation in birds.
Topics: Female; Animals; Male; Chickens; Sex Determination Processes; Gonads; Sex Differentiation; Ovary
PubMed: 37175998
DOI: 10.3390/ijms24098284