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The International Journal of... 2021Fish present remarkable malleability regarding gonadal sex fate. This phenotypic plasticity enables an organism to adapt to changes in the environment by responding with... (Review)
Review
Fish present remarkable malleability regarding gonadal sex fate. This phenotypic plasticity enables an organism to adapt to changes in the environment by responding with different phenotypes. The gonad and the brain present this extraordinary plasticity. These organs are involved in the response to environmental stressors to direct gonadal fate, inducing sex change or sex reversal in hermaphroditic and gonochoristic fish, respectively. The presence of such molecular and endocrine plasticity gives this group a large repertoire of possibilities against a continuously changing environment, resulting in the highest radiation of reproduction strategies described in vertebrates. In this review, we provide a broad and comparative view of tremendous radiation of sex determination mechanisms to direct gonadal fate. New results have established that the driving mechanism involves early response to environmental stressors by the brain plus high plasticity of gonadal differentiation and androgens as by-products of stress inactivation. In addition to the stress axis, two other major axes - the hypothalamic-pituitary-gonadal axis and the hypothalamic-pituitary-thyroid axis, which are well known for their participation in the regulation of reproduction - have been proposed to reinforce brain-gonadal interrelationships in the fate of the gonad.
Topics: Animals; Brain; Fishes; Gonads; Hypothalamo-Hypophyseal System; Reproduction; Sex Differentiation
PubMed: 32930379
DOI: 10.1387/ijdb.200072jf -
Sexual Development : Genetics,... 2016Amphibians have been widely used to study developmental biology due to the fact that embryo development takes place independently of the maternal organism and that... (Review)
Review
Amphibians have been widely used to study developmental biology due to the fact that embryo development takes place independently of the maternal organism and that observations and experimental approaches are easy. Some amphibians like Xenopus became model organisms in this field. In the first part of this article, the differentiation of the gonads in amphibians and the mechanisms governing this process are reviewed. In the second part, the state of the art about sex reversal, which can be induced by steroid hormones in general and by temperature in some species, is presented. Also information about pollutants found in the environment that could interfere with the development of the amphibian reproductive apparatus or with their reproductive physiology is given. Such compounds could play a part in the amphibian decline, since in the wild, many amphibians are endangered species.
Topics: Amphibians; Animals; Disorders of Sex Development; Gonads; Reproduction; Sex Differentiation
PubMed: 27648840
DOI: 10.1159/000448797 -
International Journal of Molecular... Apr 2022Sex determination and differentiation is an important biological process for unisexual flower development. Spinach is a model plant to study the mechanism of sex...
Sex determination and differentiation is an important biological process for unisexual flower development. Spinach is a model plant to study the mechanism of sex determination and differentiation of dioecious plant. Till now, little is known about spinach sex determination and differentiation mechanism. MicroRNAs are key factors in flower development. Herein, small RNA sequencing was performed to explore the roles of microRNAs in spinach sex determination and differentiation. As a result, 92 known and 3402 novel microRNAs were identified in 18 spinach female and male flower samples. 74 differentially expressed microRNAs were identified between female and male flowers, including 20 female-biased and 48 male-biased expression microRNAs. Target prediction identified 22 sex-biased microRNA-target pairs, which may be involved in spinach sex determination or differentiation. Among the differentially expressed microRNAs between FNS and M03, 55 microRNAs were found to reside in sex chromosome; one of them, , was functionally studied via genetic transformation. Silencing of resulted in abnormal anther while overexpression of induced early flowering, indicating was a male-promoting factor and validating the reliability of our small RNA sequencing data. Conclusively, this work can supply valuable information for exploring spinach sex determination and differentiation and provide a new insight in studying unisexual flower development.
Topics: Flowers; Gene Expression Regulation, Plant; MicroRNAs; Reproducibility of Results; Sex Differentiation; Spinacia oleracea
PubMed: 35456907
DOI: 10.3390/ijms23084090 -
Sexual Development : Genetics,... 2022Transcriptional regulators related to the invertebrate sexual regulators doublesex and mab-3 occur throughout metazoans and control sex in most animal groups. Seven of... (Review)
Review
Transcriptional regulators related to the invertebrate sexual regulators doublesex and mab-3 occur throughout metazoans and control sex in most animal groups. Seven of these DMRT genes are found in mammals, and mouse genetics has shown that one, Dmrt1, plays a crucial role in testis differentiation, both in germ cells and somatic cells. Deletions and, more recently, point mutations affecting human DMRT1 have demonstrated that its heterozygosity is associated with 46,XY complete gonadal dysgenesis. Most of our detailed knowledge of DMRT1 function in the testis, the focus of this review, derives from mouse studies, which have revealed that DMRT1 is essential for male somatic and germ cell differentiation and maintenance of male somatic cell fate after differentiation. Moreover, ectopic DMRT1 can reprogram differentiated female granulosa cells into male Sertoli-like cells. The ability of DMRT1 to control sexual cell fate likely derives from at least 3 properties. First, DMRT1 functionally collaborates with another key male sex regulator, SOX9, and possibly other proteins to maintain and reprogram sexual cell fate. Second, and related, DMRT1 appears to function as a pioneer transcription factor, binding "closed" inaccessible chromatin and promoting its opening to allow binding by other regulators including SOX9. Third, DMRT1 binds DNA by a highly unusual form of interaction and can bind with different stoichiometries.
Topics: Animals; Female; Humans; Male; Mice; Germ Cells; Gonadal Dysgenesis; Sex Differentiation; Testis; Transcription Factors
PubMed: 34515237
DOI: 10.1159/000518272 -
Asian Journal of Andrology 2017In many species, including mammals, sex determination is genetically based. The sex chromosomes that individuals carry determine sex identity. Although the genetic base... (Review)
Review
In many species, including mammals, sex determination is genetically based. The sex chromosomes that individuals carry determine sex identity. Although the genetic base of phenotypic sex is determined at the moment of fertilization, the development of testes or ovaries in the bipotential early gonads takes place during embryogenesis. During development, sex determination depends upon very few critical genes. When one of these key genes functions inappropriately, sex reversal may happen. Consequently, an individual's sex phenotype may not necessarily be consistent with the sex chromosomes that are present. For some time, it has been assumed that once the fetal choice is made between male and female in mammals, the gonadal sex identity of an individual remains stable. However, recent studies in mice have provided evidence that it is possible for the gonadal sex phenotype to be switched even in adulthood. These studies have shown that two key genes, doublesex and mad-3 related transcription factor 1 (Dmrt1) and forkhead box L2 (Foxl2), function in a Yin and Yang relationship to maintain the fates of testes or ovaries in adult mammals, and that mutations in either gene might have a dramatic effect on gonadal phenotype. Thus, adult gonad maintenance in addition to fetal sex determination may both be important for the fertility.
Topics: Animals; Female; Fertility; Forkhead Box Protein L2; Gene Expression Regulation, Developmental; Humans; Male; Sex Determination Processes; Sex Differentiation; Transcription Factors
PubMed: 28091399
DOI: 10.4103/1008-682X.194420 -
Comptes Rendus Biologies 2016Sexual reproduction is one of the most highly conserved processes in evolution. However, the genetic and cellular mechanisms making the decision of whether the... (Review)
Review
Sexual reproduction is one of the most highly conserved processes in evolution. However, the genetic and cellular mechanisms making the decision of whether the undifferentiated gonad of animal embryos develops either towards male or female are manifold and quite diverse. In vertebrates, sex-determining mechanisms range from environmental to simple or complex genetic mechanisms and different mechanisms have evolved repeatedly and independently. In species with simple genetic sex-determination, master sex-determining genes lying on sex chromosomes drive the gonadal differentiation process by switching on a developmental program, which ultimately leads to testicular or ovarian differentiation. So far, very few sex-determining genes have been identified in vertebrates and apart from mammals and birds, these genes are apparently not conserved over a larger number of related orders, families, genera, or even species. To fill this knowledge gap and to better explore genetic sex-determination, we propose a strategy (RAD-Sex) that makes use of next-generation sequencing technology to identify genetic markers that define sex-specific segments of the male or female genome.
Topics: Animals; Biological Evolution; Fishes; Humans; Reproduction; Sex; Sex Determination Processes; Sex Differentiation; Vertebrates
PubMed: 27291506
DOI: 10.1016/j.crvi.2016.05.010 -
Cells May 2022Most cultured Japanese eels () show male sex differentiation; however, natural gonadal sex differentiation has not been evaluated. In this study, this process was...
Most cultured Japanese eels () show male sex differentiation; however, natural gonadal sex differentiation has not been evaluated. In this study, this process was characterized in wild eels. Differentiated ovaries and testes were observed after the eels grew to 320 and 300 mm in total length, respectively. The youngest ovary and testis appeared at 3 and 4 years old, respectively; however, undifferentiated gonads were found up to 7 years, suggesting that sex differentiation was triggered by growth rather than aging. , , and were highly expressed in the testes, whereas , , , and were highly expressed in the ovaries. The expression of and did not differ significantly between the testis and ovary. In the ovaries, the and levels were highest in the early stages, suggesting that their function is limited to early ovarian differentiation. The , and levels tended to increase in the later stages, suggesting that they function after the initiation of ovarian differentiation. In undifferentiated gonads, dimorphic gene expression was not observed, suggesting that the molecular sex differentiation phase is short and difficult to detect. These findings provide the first demonstration of the whole course of natural gonadal sex differentiation in eels at molecular and morphological levels.
Topics: Anguilla; Animals; Female; Gonads; Male; Ovary; Sex Differentiation; Testis
PubMed: 35563858
DOI: 10.3390/cells11091554 -
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 -
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