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Sexual Development : Genetics,... 2021Atheriniform fishes have recently emerged as attractive models for evolutionary, ecological, and molecular/physiological studies on sex determination. Many species in... (Review)
Review
Atheriniform fishes have recently emerged as attractive models for evolutionary, ecological, and molecular/physiological studies on sex determination. Many species in this group have marked temperature-dependent sex determination (TSD) and yet many species also have a sex determinant gene that provides a strong drive for male differentiation. Thus, in these species the 2 forms of sex determination that were once considered to be mutually exclusive, environmental (ESD) and genotypic (GSD) sex determination, can coexist at environmentally relevant conditions. Here, we review the current knowledge on sex determination in atheriniform fishes with emphasis on the molecular and physiological mechanisms of ESD and GSD, the coexistence and cross-talk between these 2 mechanisms, the possibility of extragonadal transduction of environmental information and/or extragonadal onset of sex determination, and the results of field studies applying novel tools such as otolith increment analysis and molecular markers of genetic sex developed for selected New World and Old World atheriniform species. We also discuss the existence of molecular and histological mechanisms to prevent the discrepant differentiation in parts of the gonads because of ambiguous or conflicting environmental and genetic signals and particularly the possibility that the female is the default state in these species.
Topics: Animals; Female; Fishes; Genotype; Gonads; Male; Sex Determination Analysis; Sex Determination Processes; Sex Differentiation; Temperature
PubMed: 33951664
DOI: 10.1159/000515191 -
Sexual Development : Genetics,... 2021During the process of sex determination, a germ-cell-containing undifferentiated gonad is converted into either a male or a female reproductive organ. Both the... (Review)
Review
During the process of sex determination, a germ-cell-containing undifferentiated gonad is converted into either a male or a female reproductive organ. Both the composition of sex chromosomes and the environment determine sex in vertebrates. It is assumed that transcription level regulation drives this cascade of mechanisms; however, transcription factors can alter gene expression beyond transcription initiation by controlling pre-mRNA splicing and thereby mRNA isoform production. Using the key time window in sex determination and gonad development in mice, it has been reported that new non-transcriptional events, such as alternative splicing, could play a key role in sex determination in mammals. We know the role of key regulatory factors, like WT1(+/-KTS) or FGFR2(b/c) in pre-mRNA splicing and sex determination, indicating that important steps in the vertebrate sex determination process probably operate at a post-transcriptional level. Here, we discuss the role of pre-mRNA splicing regulators in sex determination in vertebrates, focusing on the new RNA-seq data reported from mice fetal gonadal transcriptome.
Topics: Alternative Splicing; Animals; Female; Gonads; Male; Mice; Sex Determination Processes; Sex Differentiation; Vertebrates
PubMed: 34583366
DOI: 10.1159/000519218 -
Genome Biology and Evolution Jun 2018Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several...
Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several gonad development features that differentiate tetrapods and fishes are likely to be, at least in part, related to the water-to-land transition. The collection of information from basal sarcopterygians, coelacanths, and lungfishes, is crucial to improve our understanding of the molecular evolution of pathways involved in reproductive functions, since these organisms are generally regarded as "living fossils" and as the direct ancestors of tetrapods. Here, we report for the first time the characterization of >50 genes related to sex differentiation and gametogenesis in Latimeria menadoensis and Protopterus annectens. Although the expression profiles of most genes is consistent with the intermediate position of basal sarcopterygians between actinopterygian fish and tetrapods, their phylogenetic placement and presence/absence patterns often reveal a closer affinity to the tetrapod orthologs. On the other hand, particular genes, for example, the male gonad factor gsdf (Gonadal Soma-Derived Factor), provide examples of ancestral traits shared with actinopterygians, which disappeared in the tetrapod lineage.
Topics: Animals; Chordata; Evolution, Molecular; Fishes; Gametogenesis; Male; Phylogeny; Reproduction; Sex Differentiation
PubMed: 29850809
DOI: 10.1093/gbe/evy101 -
Sexual Development : Genetics,... 2023Reptiles and amphibians provide untapped potential for discovering how a diversity of genetic pathways and environmental conditions are incorporated into developmental... (Review)
Review
BACKGROUND
Reptiles and amphibians provide untapped potential for discovering how a diversity of genetic pathways and environmental conditions are incorporated into developmental processes that can lead to similar functional outcomes. These groups display a multitude of reproductive strategies, and whereas many attributes are conserved within groups and even across vertebrates, several aspects of sexual development show considerable variation.
SUMMARY
In this review, we focus our attention on the development of the reptilian and amphibian ovary. First, we review and describe the events leading to ovarian development, including sex determination and ovarian maturation, through a comparative lens. We then describe how these events are influenced by environmental factors, focusing on temperature and exposure to anthropogenic chemicals. Lastly, we identify critical knowledge gaps and future research directions that will be crucial to moving forward in our understanding of ovarian development and the influences of the environment in reptiles and amphibians.
KEY MESSAGES
Reptiles and amphibians provide excellent models for understanding the diversity of sex determination strategies and reproductive development. However, a greater understanding of the basic biology of these systems is necessary for deciphering the adaptive and potentially disruptive implications of embryo-by-environment interactions in a rapidly changing world.
Topics: Animals; Female; Reptiles; Amphibians; Sex Differentiation; Ovary; Temperature; Sex Determination Processes
PubMed: 36380624
DOI: 10.1159/000526009 -
Cellular and Molecular Life Sciences :... Jun 1999Amphibians employ a genetic mechanism of sex determination, according to all available information on sex chromosomes or breeding tests. Sex reversal allows breeding... (Review)
Review
Amphibians employ a genetic mechanism of sex determination, according to all available information on sex chromosomes or breeding tests. Sex reversal allows breeding tests to establish which sex is heterogametic and provides an indication of the mechanism of sex determination. Cases of spontaneous and experimental sex reversal (by temperature, hormones or surgery) are reviewed and illustrated by previously unpublished studies on crested newts. These newts respond conventionally to temperature and hormone treatment but provide anomalous results from breeding tests. It is suggested that both the evolution from temperature dependency to a genetic switch and from ZZ/ZW to XX/XY are superimposed on a generally uniform mechanism of sex determination in all vertebrates.
Topics: Amphibians; Animals; Castration; Disorders of Sex Development; Female; Gonadal Steroid Hormones; Gonads; Larva; Male; Sex Determination Processes; Sex Differentiation; Temperature; X Chromosome; Y Chromosome
PubMed: 10412371
DOI: 10.1007/s000180050343 -
Developmental Dynamics : An Official... Apr 2013Epigenetics is commonly defined as the study of heritable changes in gene function that cannot be explained by changes in DNA sequence. The three major epigenetic... (Review)
Review
Epigenetics is commonly defined as the study of heritable changes in gene function that cannot be explained by changes in DNA sequence. The three major epigenetic mechanisms for gene expression regulation include DNA methylation, histone modifications, and non-coding RNAs. Epigenetic mechanisms provide organisms with the ability to integrate genomic and environmental information to modify the activity of their genes for generating a particular phenotype. During development, cells differentiate, acquire, and maintain identity through changes in gene expression. This is crucial for sex determination and differentiation, which are among the most important developmental processes for the proper functioning and perpetuation of species. This review summarizes studies showing how epigenetic regulatory mechanisms contribute to sex determination and reproductive organ formation in plants, invertebrates, and vertebrates. Further progress will be made by integrating several approaches, including genomics and Next Generation Sequencing to create epigenetic maps related to different aspects of sex determination and gonadogenesis. Epigenetics will also contribute to understand the etiology of several disorders of sexual development. It also might play a significant role in the control of reproduction in animal farm production and will aid in recognizing the environmental versus genetic influences on sex determination of sensitive species in a global change scenario.
Topics: Animals; DNA Methylation; Disorders of Sex Development; Environment; Epigenesis, Genetic; Female; Gonads; Histones; Humans; Male; RNA, Untranslated; Sex Determination Processes; Sex Differentiation
PubMed: 23335256
DOI: 10.1002/dvdy.23924 -
PloS One 2022A 180-day experiment was conducted to evaluate the effects of density on sex differentiation, sexual dimorphism, cortisol level, and stress related gene expression....
A 180-day experiment was conducted to evaluate the effects of density on sex differentiation, sexual dimorphism, cortisol level, and stress related gene expression. Yellow perch, Perca flavescens, with initial mean body weight of 0.03 ± 0.001 g were reared in three different stocking densities: 1, 2, and 4 fish/L, termed as low (LD), moderate (MD), and high (HD) density, respectively, in a flow-through tank system. Results showed no significant differences in sex ratio in all density groups compared to normal population 1:1, and sexual size dimorphism (SSD) appeared when male and female were as small as the mean size reaching 11.5 cm and 12.3 cm in total length (TL) or 13.2g and 16.9g in body weight (BW), respectively. This female-biased sexual growth dimorphism was more pronounced in LD, although it was observed across all density groups. A significantly higher condition factor (K) of females than males in the LD group, and significantly higher R values of LD and MD than HD with the length/weight (L/W) linear relationships in females, were observed. Parallelly, fish reared in LD showed significantly higher mean body weight than those in the MD and HD groups, but there were no significant differences between the MD and HD. Similar results were also observed in all the other parameters of weight gain, specific growth rate (SGR), condition factor (K), and survival. These findings suggested that high density not only affected growth itself, but also affected SSD, growth trajectory or body shape, and general wellbeing in fish, especially in females. There were no significant differences in gonadosomatic index (GSI) and viscerosomatic index (VSI) among all the density groups; however, the hepatosomatic index (HSI) of LD was significantly higher than MD and HD, suggesting high density affected liver reserves or functions. Physiologically, plasma cortisol level was significantly highest in the LD among all groups, followed by MD, and lowest in HD. At the molecular level, the expression of the 70-kDa heat shock protein (Hsp70), glutathione peroxidase (GPx), and superoxide dismutase (SOD) genes involved in cellular stress were significantly upregulated in the HD group. The most significantly downregulated expression of these genes was consistently observed in the MD when compared to the LD and HD groups. In conclusion, increasing density induced chronic stress in yellow perch without affecting sex differentiation, but negatively affected expression of stress-related genes and mobilization of liver reserve, resulting in poorer wellbeing and reduced SSD, growth, and survival.
Topics: Animals; Body Weight; Female; Gene Expression; Hydrocortisone; Male; Perches; Sex Characteristics; Sex Differentiation
PubMed: 35507560
DOI: 10.1371/journal.pone.0267904 -
Nature Neuroscience Jun 2011In the twentieth century, the dominant model of sexual differentiation stated that genetic sex (XX versus XY) causes differentiation of the gonads, which then secrete... (Review)
Review
In the twentieth century, the dominant model of sexual differentiation stated that genetic sex (XX versus XY) causes differentiation of the gonads, which then secrete gonadal hormones that act directly on tissues to induce sex differences in function. This serial model of sexual differentiation was simple, unifying and seductive. Recent evidence, however, indicates that the linear model is incorrect and that sex differences arise in response to diverse sex-specific signals originating from inherent differences in the genome and involve cellular mechanisms that are specific to individual tissues or brain regions. Moreover, sex-specific effects of the environment reciprocally affect biology, sometimes profoundly, and must therefore be integrated into a realistic model of sexual differentiation. A more appropriate model is a parallel-interactive model that encompasses the roles of multiple molecular signals and pathways that differentiate males and females, including synergistic and compensatory interactions among pathways and an important role for the environment.
Topics: Animals; Brain; Female; Humans; Male; Models, Biological; Neural Pathways; Sex Differentiation; Sexual Development
PubMed: 21613996
DOI: 10.1038/nn.2834 -
Nature Reviews. Endocrinology Oct 2014Mammalian sex determination is the unique process whereby a single organ, the bipotential gonad, undergoes a developmental switch that promotes its differentiation into... (Review)
Review
Mammalian sex determination is the unique process whereby a single organ, the bipotential gonad, undergoes a developmental switch that promotes its differentiation into either a testis or an ovary. Disruptions of this complex genetic process during human development can manifest as disorders of sex development (DSDs). Sex development can be divided into two distinct processes: sex determination, in which the bipotential gonads form either testes or ovaries, and sex differentiation, in which the fully formed testes or ovaries secrete local and hormonal factors to drive differentiation of internal and external genitals, as well as extragonadal tissues such as the brain. DSDs can arise from a number of genetic lesions, which manifest as a spectrum of gonadal (gonadal dysgenesis to ovotestis) and genital (mild hypospadias or clitoromegaly to ambiguous genitalia) phenotypes. The physical attributes and medical implications associated with DSDs confront families of affected newborns with decisions, such as gender of rearing or genital surgery, and additional concerns, such as uncertainty over the child's psychosexual development and personal wishes later in life. In this Review, we discuss the underlying genetics of human sex determination and focus on emerging data, genetic classification of DSDs and other considerations that surround gender development and identity in individuals with DSDs.
Topics: Animals; Disorders of Sex Development; Female; Genetic Variation; Humans; Male; Mutation; Sex Differentiation; Sexual Development; Sexual Dysfunctions, Psychological
PubMed: 25091731
DOI: 10.1038/nrendo.2014.130 -
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