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Current Topics in Developmental Biology 2019Over the last several decades zebrafish (Danio rerio) has become a major model organism for the study of vertebrate development and physiology. Given this, it may be... (Review)
Review
Over the last several decades zebrafish (Danio rerio) has become a major model organism for the study of vertebrate development and physiology. Given this, it may be surprising how little is known about the mechanism that zebrafish use to determine sex. While zebrafish are a gonochoristic species (having two sexes) that do not switch sex as adults, it was appreciated early on that sex ratios obtained from breeding lab domesticated lines were not typically a 1:1 ratio of male and female, suggesting that sex was not determined by a strict chromosomal mechanism. Here we will review the recent progress toward defining the genetic mechanism for sex determination in both wild and domesticated zebrafish.
Topics: Animals; Gene Expression Regulation, Developmental; Sex Determination Processes; Sex Differentiation; Zebrafish; Zebrafish Proteins
PubMed: 30999973
DOI: 10.1016/bs.ctdb.2019.02.004 -
Sexual Development : Genetics,... 2021All crocodilians exhibit temperature-dependent sex determination without sex chromosomes. This temperature dependency can be overridden by exposure to estrogen via... (Review)
Review
All crocodilians exhibit temperature-dependent sex determination without sex chromosomes. This temperature dependency can be overridden by exposure to estrogen via estrogen receptor 1. Thus, the sex ratio of crocodilian species is vulnerable to estrogenic xenobiotics. Multiple investigations of the mechanism and effects of xenobiotics in crocodilian species have been conducted since the early 1990s. This review focuses on the impact of xenobiotics on sex determination rather than gonadal functions in crocodilians. The thermosensitive and estrogen-sensitive periods that commit the bipotential gonad to develop as an ovary end by stages 24.5 and 25.3, respectively. In contrast, it is ambiguous when the estrogen-sensitive stage begins for ovarian development, although the thermosensitive period for ovarian development initiates around developmental stage 15 at an extreme female-producing temperature of 30°C. To accurately assess the effect of xenoestrogens on sex ratio in crocodilians, it is critical to collect eggs before the sex-determining period and to incubate them under precisely controlled temperatures. A well-studied system of xenobiotic effects on crocodilians is Lake Apopka (FL, USA), an EPA superfund clean-up site heavily contaminated with Dieldrin, Endrin, and p,p'-DDE. The sum of estimated estrogenicity of xenobiotics measured in Lake Apopka was insufficient to activate the estrogen receptor 1 of Alligator mississippiensis, which is an essential receptor to induce ovarian development. Although juvenile A. mississippiensis showed gonadal alterations in sex hormone production and histology, the environmentally relevant concentration of xenobiotics in Lake Apopka was unlikely to alter the sex ratio of A. mississippiensis. Experimental exposure to xenobiotics such as 17α-ethynylestradiol, p,p'-dichlorodiphenyldichloroethylene, and 2,3,7,8-tetrachlorodibenzodioxin at environmentally relevant concentrations in ovo induced more female offspring in A. mississippiensis as compared with the control group. Bisphenol-A, atrazine, 2,4-dichlorophenoxyacetic acid, endosulfan, and Corexit did not alter the sex ratio of A. mississippiensis or Caiman latirostris under the tested conditions. Egg-incubation temperature has pronounced effects on estrogen sensitivity in crocodilian sex determination. Therefore, crocodilians are vulnerable to xenobiotic contamination and climate change in the wild. It is vital to further investigate the detailed mechanism and effects of environmental xenobiotics in crocodilian sex determination to mitigate their effect on sex ratio and conserve this ancient lineage.
Topics: Alligators and Crocodiles; Animals; Estrogens; Female; Sex Differentiation; Sex Ratio; Xenobiotics
PubMed: 34161954
DOI: 10.1159/000515724 -
BioEssays : News and Reviews in... Jan 2011Animals have evolved a bewildering diversity of mechanisms to determine the two sexes. Studies of sex determination genes--their history and function--in non-model... (Review)
Review
Animals have evolved a bewildering diversity of mechanisms to determine the two sexes. Studies of sex determination genes--their history and function--in non-model insects and Drosophila have allowed us to begin to understand the generation of sex determination diversity. One common theme from these studies is that evolved mechanisms produce activities in either males or females to control a shared gene switch that regulates sexual development. Only a few small-scale changes in existing and duplicated genes are sufficient to generate large differences in sex determination systems. This review summarises recent findings in insects, surveys evidence of how and why sex determination mechanisms can change rapidly and suggests fruitful areas of future research.
Topics: Animals; Biological Evolution; Female; Genes; Genetic Variation; Insecta; Male; Models, Animal; Mutation; Sex Characteristics; Sex Determination Processes; Sex Differentiation; Species Specificity
PubMed: 21110346
DOI: 10.1002/bies.201000043 -
Trends in Neurosciences Jan 2024Sex differences are found across brain regions, behaviors, and brain diseases. Sexual differentiation of the brain is initiated prenatally but it continues throughout... (Review)
Review
Sex differences are found across brain regions, behaviors, and brain diseases. Sexual differentiation of the brain is initiated prenatally but it continues throughout life, as a result of the interaction of three major factors: gonadal hormones, sex chromosomes, and the environment. These factors are thought to act, in part, via epigenetic mechanisms which control chromatin and transcriptional states in brain cells. In this review, we discuss evidence that epigenetic mechanisms underlie sex-specific neurobehavioral changes during critical organizational periods, across the estrous cycle, and in response to diverse environments throughout life. We further identify future directions for the field that will provide novel mechanistic insights into brain sex differences, inform brain disease treatments and women's brain health in particular, and apply to people across genders.
Topics: Humans; Male; Female; Sex Characteristics; Brain; Epigenesis, Genetic; Brain Diseases; Sex Differentiation
PubMed: 37968206
DOI: 10.1016/j.tins.2023.09.007 -
BMC Genomics Apr 2023Red-tail catfish (Hemibagrus wyckioides) is an important commercially farmed catfish in southern China. Males of red-tail catfish grow faster than females, suggesting...
BACKGROUND
Red-tail catfish (Hemibagrus wyckioides) is an important commercially farmed catfish in southern China. Males of red-tail catfish grow faster than females, suggesting that all-male catfish will produce more significant economic benefits in aquaculture practice. However, little research has been reported on sex determination and gonadal development in red-tail catfish.
RESULTS
In this study, we performed the first transcriptomic analysis of male and female gonads at four developmental stages at 10, 18, 30, and 48 days post hatching (dph) using RNA-seq technology. A total of 23,588 genes were screened in 24 sequenced samples, of which 28, 213, 636, and 1381 differentially expressed genes (DEGs) were detected at four developmental stages, respectively. Seven candidate genes of sex determination and differentiation were further identified. Real-time quantitative PCR (RT-qPCR) further confirmed that anti-Mullerian hormone (amh), growth differentiation factor 6a (gdf6a), testis-specific gene antigen 10 (tsga10), and cytochrome P450 family 17 subfamily A (cyp17a) were highly expressed mainly in the male, while cytochrome P450 family 19 subfamily A polypeptide 1b (cyp19a1b), forkhead box L2 (foxl2), and hydroxysteroid 17-beta dehydrogenase 1 (hsd17b1) were highly expressed in the female. The KEGG pathway enrichment data showed that these identified DEGs were mainly involved in steroid hormone biosynthesis and TGF-β signaling pathways.
CONCLUSIONS
Based on RNA-seq data of gonads at the early developmental stages, seven DEGs shared by the four developmental stages were identified, among which amh and gdf6a may be the male-biased expression genes, while foxl2, cyp19a1b and hsd17b1 may be the female-biased expression genes in red-tail catfish. Our study will provide crucial genetic information for the research on sex control in red-tail catfish, as well as for exploring the evolutionary processes of sex determination mechanisms in fish.
Topics: Animals; Female; Male; Transcriptome; Catfishes; Gonads; Ovary; Gene Expression Profiling; Perciformes; Sex Differentiation; Gene Expression Regulation, Developmental; Sex Determination Processes
PubMed: 37024792
DOI: 10.1186/s12864-023-09264-x -
Glia Jun 2020Microglia, the innate immune cells of the brain, have recently been removed from the position of mere sentinels and promoted to the role of active sculptors of... (Review)
Review
Microglia, the innate immune cells of the brain, have recently been removed from the position of mere sentinels and promoted to the role of active sculptors of developing circuits and cells. Alongside their functions in normal brain development, microglia coordinate sexual differentiation of the brain, a set of processes which vary by region and endpoint like that of microglia function itself. In this review, we highlight the ways microglia are both targets and drivers of brain sexual differentiation. We examine the factors that may drive sex differences in microglia, with a special focus on how changing microenvironments in the developing brain dictate microglia phenotypes and discuss how their diverse functions sculpt lasting sex-specific changes in the brain. Finally, we consider how sex-specific early life environments contribute to epigenetic programming and lasting sex differences in microglia identity.
Topics: Animals; Brain; Cell Differentiation; Humans; Microglia; Neurons; Sex Characteristics; Sex Differentiation
PubMed: 31691400
DOI: 10.1002/glia.23740 -
Glia Jun 2020Sexual differentiation of the brain during early development likely underlies the strong sex biases prevalent in many neurological conditions. Mounting evidence... (Review)
Review
Sexual differentiation of the brain during early development likely underlies the strong sex biases prevalent in many neurological conditions. Mounting evidence indicates that microglia, the innate immune cells of the central nervous system, are intricately involved in these sex-specific processes of differentiation. In this review, we synthesize literature demonstrating sex differences in microglial number, morphology, transcriptional state, and functionality throughout spatiotemporal development as well as highlight current literature regarding ontogeny of microglia. Along with vanRyzin et al. in this issue, we explore the idea that differences in microglia imparted by chromosomal or ontogeny-related programming can influence microglial-driven sexual differentiation of the brain, as well as the idea that extrinsic differences in the male and female brain microenvironment may in turn impart sex differences in microglia.
Topics: Animals; Brain; Humans; Male; Microglia; Nervous System Diseases; Neurons; Sex Characteristics; Sex Differentiation
PubMed: 31743527
DOI: 10.1002/glia.23753 -
Hormones and Behavior Apr 2020This paper is part of the celebration of the 50th anniversary of founding of the journal Hormones and Behavior, the official journal of the Society for Behavioral... (Review)
Review
This paper is part of the celebration of the 50th anniversary of founding of the journal Hormones and Behavior, the official journal of the Society for Behavioral Neuroendocrinology. All sex differences in phenotypic development stem from the sexual imbalance in X and Y chromosomes, which are the only known differences in XX and XY zygotes. The sex chromosome genes act within cells to cause differences in phenotypes of XX and XY cells throughout the body. In the gonad, they determine the type of gonad, leading to differences in secretion of testicular vs. ovarian hormones, which cause further sex differences in tissue function. These current ideas of sexual differentiation are briefly contrasted with a hormones-only view of sexual differentiation of the last century. The multiple, independent action of diverse sex-biasing agents means that sex-biased factors can be synergistic, increasing sex differences, or compensatory, making the two sexes more equal. Several animal models have been fruitful in demonstrating sex chromosome effects, and interactions with gonadal hormones. MRI studies of human brains demonstrate variation in brain structure associated with both differences in gonadal hormones, and in the number of X and Y chromosomes. Five unanswered questions are posed as a challenge to future investigators to improve understanding of sexual differentiation throughout the body.
Topics: Animals; Biomedical Research; Brain; Embryonic Development; Female; History, 20th Century; History, 21st Century; Humans; Male; Models, Animal; Neuroendocrinology; Phenotype; Sex Characteristics; Sex Differentiation
PubMed: 31991182
DOI: 10.1016/j.yhbeh.2020.104691 -
International Journal of Molecular... Dec 2019Androgens and anti-Müllerian hormone (AMH), secreted by the foetal testis, are responsible for the development of male reproductive organs and the regression of female... (Review)
Review
Androgens and anti-Müllerian hormone (AMH), secreted by the foetal testis, are responsible for the development of male reproductive organs and the regression of female anlagen. Virilization of the reproductive tract in association with the absence of Müllerian derivatives in the XX foetus implies the existence of testicular tissue, which can occur in the presence or absence of SRY. Recent advancement in the knowledge of the opposing gene cascades driving to the differentiation of the gonadal ridge into testes or ovaries during early foetal development has provided insight into the molecular explanation of XX maleness.
Topics: Animals; Disorders of Sex Development; Fetus; Humans; Male; Mammals; Models, Biological; Sex Differentiation
PubMed: 31816857
DOI: 10.3390/ijms20236089 -
Philosophical Transactions of the Royal... Aug 2021Triggers and biological processes controlling male or female gonadal differentiation vary in vertebrates, with sex determination (SD) governed by environmental factors... (Review)
Review
Triggers and biological processes controlling male or female gonadal differentiation vary in vertebrates, with sex determination (SD) governed by environmental factors or simple to complex genetic mechanisms that evolved repeatedly and independently in various groups. Here, we review sex evolution across major clades of vertebrates with information on SD, sexual development and reproductive modes. We offer an up-to-date review of divergence times, species diversity, genomic resources, genome size, occurrence and nature of polyploids, SD systems, sex chromosomes, SD genes, dosage compensation and sex-biased gene expression. Advances in sequencing technologies now enable us to study the evolution of SD at broader evolutionary scales, and we now hope to pursue a integrative research initiative across vertebrates. The vertebrate comprises interdisciplinary and integrated information on sexual differentiation, development and reproduction at all biological levels, from genomes, transcriptomes and proteomes, to the organs involved in sexual and sex-specific processes, including gonads, secondary sex organs and those with transcriptional sex-bias. The also includes ontogenetic and behavioural aspects of sexual differentiation, including malfunction and impairment of SD, sexual differentiation and fertility. Starting from data generated by high-throughput approaches, we encourage others to contribute expertise to building understanding of the of many key vertebrate species. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)'.
Topics: Animals; Biological Evolution; Evolution, Molecular; Female; Genome Size; Male; Ovary; Sex Chromosomes; Sex Determination Processes; Sex Differentiation; Testis; Vertebrates
PubMed: 34247497
DOI: 10.1098/rstb.2020.0426