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Sexual Development : Genetics,... 2017Sex chromosomes in most amphibians are homomorphic (undifferentiated) in both sexes and are characterized by frequent turnover. This is in sharp contrast to sex... (Review)
Review
Sex chromosomes in most amphibians are homomorphic (undifferentiated) in both sexes and are characterized by frequent turnover. This is in sharp contrast to sex chromosomes in 2 major vertebrate groups, the mammals and birds, where they are heteromorphic in one sex and are highly conserved. Sex-determining mechanisms in anuran amphibians, particularly in relation to the turnover of sex-determining genes and sex chromosomes, are summarized and their evolution is discussed.
Topics: Amphibians; Animals; Female; Male; Sex Chromosomes; Sex Determination Analysis; Sex Determination Processes
PubMed: 29241181
DOI: 10.1159/000485270 -
Taiwanese Journal of Obstetrics &... Sep 2020Fetal sex discordance is an entity that is becoming more frequent due to the expansion of the cfDNA for prenatal diagnosis. Its incidence can be estimated in 1/1500-2000... (Review)
Review
Fetal sex discordance is an entity that is becoming more frequent due to the expansion of the cfDNA for prenatal diagnosis. Its incidence can be estimated in 1/1500-2000 pregnancies, a frequency as high as that of some common chromosomopathies. The causes of this phenomenon are multiple and diverse, ranging from laboratory errors to important pathologies such as disorders of sexual differentiation. The management of a case of fetal sex discordance must be structured, starting with the review of the clinical history and the tests performed, and may require the performance of invasive tests to reach a diagnosis. Prevention through adequate pretest counseling and ultrasound confirmation can help to reduce its incidence.
Topics: Cell-Free Nucleic Acids; Disorders of Sex Development; Female; Humans; Maternal Serum Screening Tests; Pregnancy; Sex Characteristics; Sex Determination Analysis; Ultrasonography, Prenatal
PubMed: 32917312
DOI: 10.1016/j.tjog.2020.07.004 -
Sexual Development : Genetics,... 2021Studying environmental sex determination (ESD) in cichlids provides a phylogenetic and comparative approach to understand the evolution of the underlying mechanisms,... (Review)
Review
Studying environmental sex determination (ESD) in cichlids provides a phylogenetic and comparative approach to understand the evolution of the underlying mechanisms, their impact on the evolution of the overlying systems, and the neuroethology of life history strategies. Natural selection normally favors parents who invest equally in the development of male and female offspring, but evolution may favor deviations from this 50:50 ratio when environmental conditions produce an advantage for doing so. Many species of cichlids demonstrate ESD in response to water chemistry (temperature, pH, and oxygen concentration). The relative strengths of and the exact interactions between these factors vary between congeners, demonstrating genetic variation in sensitivity. The presence of sizable proportions of the less common sex towards the environmental extremes in most species strongly suggests the presence of some genetic sex-determining loci acting in parallel with the ESD factors. Sex determination and differentiation in these species does not seem to result in the organization of a final and irreversible sexual fate, so much as a life-long ongoing battle between competing male- and female-determining genetic and hormonal networks governed by epigenetic factors. We discuss what is and is not known about the epigenetic mechanism behind the differentiation of both gonads and sex differences in the brain. Beyond the well-studied tilapia species, the 2 best-studied dwarf cichlid systems showing ESD are the South American genus Apistogramma and the West African genus Pelvicachromis. Both species demonstrate male morphs with alternative reproductive tactics. We discuss the further neuroethology opportunities such systems provide to the study of epigenetics of alternative life history strategies and other behavioral variation.
Topics: Animals; Cichlids; Epigenesis, Genetic; Female; Gonads; Male; Phylogeny; Sex Determination Analysis
PubMed: 34433170
DOI: 10.1159/000517197 -
JAMA Aug 2011Noninvasive prenatal determination of fetal sex using cell-free fetal DNA provides an alternative to invasive techniques for some heritable disorders. In some countries... (Meta-Analysis)
Meta-Analysis Review
CONTEXT
Noninvasive prenatal determination of fetal sex using cell-free fetal DNA provides an alternative to invasive techniques for some heritable disorders. In some countries this testing has transitioned to clinical care, despite the absence of a formal assessment of performance.
OBJECTIVE
To document overall test performance of noninvasive fetal sex determination using cell-free fetal DNA and to identify variables that affect performance.
DATA SOURCES
Systematic review and meta-analysis with search of PubMed (January 1, 1997-April 17, 2011) to identify English-language human studies reporting primary data. References from review articles were also searched.
STUDY SELECTION AND DATA EXTRACTION
Abstracts were read independently to identify studies reporting primary data suitable for analysis. Covariates included publication year, sample type, DNA amplification methodology, Y chromosome sequence, and gestational age. Data were independently extracted by 2 reviewers.
RESULTS
From 57 selected studies, 80 data sets (representing 3524 male-bearing pregnancies and 3017 female-bearing pregnancies) were analyzed. Overall performance of the test to detect Y chromosome sequences had the following characteristics: sensitivity, 95.4% (95% confidence interval [CI], 94.7%-96.1%) and specificity, 98.6% (95% CI, 98.1%-99.0%); diagnostic odds ratio (OR), 885; positive predictive value, 98.8%; negative predictive value, 94.8%; area under curve (AUC), 0.993 (95% CI, 0.989-0.995), with significant interstudy heterogeneity. DNA methodology and gestational age had the largest effects on test performance. Methodology test characteristics were AUC, 0.988 (95% CI, 0.979-0.993) for polymerase chain reaction (PCR) and AUC, 0.996 (95% CI, 0.993-0.998) for real-time quantitative PCR (RTQ-PCR) (P = .02). Gestational age test characteristics were AUC, 0.989 (95% CI, 0.965-0.998) (<7 weeks); AUC, 0.994 (95% CI, 0.987-0.997) (7-12 weeks); AUC, 0.992 (95% CI, 0.983-0.996) (13-20 weeks); and AUC, 0.998 (95% CI, 0.990-0.999) (>20 weeks) (P = .02 for comparison of diagnostic ORs across age ranges). RTQ-PCR (sensitivity, 96.0%; specificity, 99.0%) outperformed conventional PCR (sensitivity, 94.0%; specificity, 97.3%). Testing after 20 weeks (sensitivity, 99.0%; specificity, 99.6%) outperformed testing prior to 7 weeks (sensitivity, 74.5%; specificity, 99.1%), testing at 7 through 12 weeks (sensitivity, 94.8%; specificity, 98.9%), and 13 through 20 weeks (sensitivity, 95.5%; specificity, 99.1%).
CONCLUSIONS
Despite interstudy variability, performance was high using maternal blood. Sensitivity and specificity for detection of Y chromosome sequences was greatest using RTQ-PCR after 20 weeks' gestation. Tests using urine and tests performed before 7 weeks' gestation were unreliable.
Topics: Chromosomes, Human, Y; DNA; Female; Fetus; Humans; Male; Polymerase Chain Reaction; Predictive Value of Tests; Pregnancy; Prenatal Diagnosis; Sensitivity and Specificity; Sequence Analysis, DNA; Sex Determination Analysis
PubMed: 21828326
DOI: 10.1001/jama.2011.1114 -
Sexual Development : Genetics,... 2021Animals determine their sex genetically (GSD: genetic sex determination) and/or environmentally (ESD: environmental sex determination). Medaka (Oryzias latipes) employ a... (Review)
Review
Animals determine their sex genetically (GSD: genetic sex determination) and/or environmentally (ESD: environmental sex determination). Medaka (Oryzias latipes) employ a XX/XY GSD system, however, they display female-to-male sex reversal in response to various environmental changes such as temperature, hypoxia, and green light. Interestingly, we found that 5 days of starvation during sex differentiation caused female-to-male sex reversal. In this situation, the metabolism of pantothenate and fatty acid synthesis plays an important role in sex reversal. Metabolism is associated with other biological factors such as germ cells, HPG axis, lipids, and epigenetics, and supplys substances and acts as signal transducers. In this review, we discuss the importance of metabolism during sex differentiation and how metabolism contributes to sex differentiation.
Topics: Animals; Female; Germ Cells; Male; Oryzias; Sex Determination Analysis; Sex Determination Processes; Sex Differentiation
PubMed: 34284403
DOI: 10.1159/000515281 -
Sexual Development : Genetics,... 2021The discovery in mammals that fetal testes are required in order to develop the male phenotype inspired research efforts to elucidate the mechanisms underlying gonadal... (Review)
Review
The discovery in mammals that fetal testes are required in order to develop the male phenotype inspired research efforts to elucidate the mechanisms underlying gonadal sex determination and differentiation in vertebrates. A pioneer work in 1966 that demonstrated the influence of incubation temperature on sexual phenotype in some reptilian species triggered great interest in the environment's role as a modulator of plasticity in sex determination. Several chelonian species have been used as animal models to test hypotheses concerning the mechanisms involved in temperature-dependent sex determination (TSD). This brief review intends to outline the history of scientific efforts that corroborate our current understanding of the state-of-the-art in TSD using chelonian species as a reference.
Topics: Animals; Gonads; Male; Sex Determination Analysis; Sex Determination Processes; Sex Differentiation; Temperature; Turtles
PubMed: 34167126
DOI: 10.1159/000515296 -
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 -
British Medical Journal Nov 1979
Topics: Animals; Disorders of Sex Development; Female; Humans; Male; Mice; Sex Chromosome Aberrations; Sex Chromosomes; Sex Determination Analysis
PubMed: 519310
DOI: No ID Found -
Integrative Zoology Jan 2022Identifying the mechanism for sex determination in amphibians is challenging. Very little is known about sex determination mechanisms of Rana dybowskii, a species of...
Identifying the mechanism for sex determination in amphibians is challenging. Very little is known about sex determination mechanisms of Rana dybowskii, a species of importance to evolutionary and conservation biology. We screened for sex-linked molecular markers in R. dybowskii in China using target region amplification polymorphism with 2 fixed primers against the sequences of Dmrt1. We found 2 male-linked molecular markers in R. dybowskii, which were 222 bp and 261 bp long. The detection rates of 222 bp marker in males form Xinglong, Huadian, and Dandong were 93.79%, 69.64%, and 13.64%, respectively, while the rate in females from Huadian was 27.50%. Besides, the detection rates of 261 bp marker in the above 3 regions were only observed in males at the rate of 93.79%, 87.50%, and 32.73%, respectively. The inheritance patterns of sex-linked molecular markers showed that the 2 sex-linked molecular markers were heterozygous. Compared to the XY-male parent, progeny from XX-pseudo-male parent possessed lower sex reversal ratio at the same rearing temperature, and the proportion of female froglets from an XX-pseudo-male parent was more than 95% at low rearing temperature (15°C). Our findings suggest that R. dybowskii displays male heterogamety, and the 2 sex-linked molecular markers may have a guiding significance for the protection and utilization of R. dybowskii.
Topics: Animals; Biological Evolution; China; Female; Genetic Markers; Male; Polymorphism, Genetic; Ranidae; Sex Determination Analysis
PubMed: 34254736
DOI: 10.1111/1749-4877.12577 -
Sexual Development : Genetics,... 2016Sex determination or the commitment of the embryo to its sexual fate is a fundamental developmental process with paramount consequences in ecology and evolution. This... (Review)
Review
Sex determination or the commitment of the embryo to its sexual fate is a fundamental developmental process with paramount consequences in ecology and evolution. This process, whether triggered by environmental factors or genotypic constitution, can be derailed by environmental contaminants that alter the endocrine system, which is a key component of the regulatory network underlying vertebrate sex determination. Here, we review the molecular basis of sex determination, the endocrine components of its regulation, the maternal and endogenous sources of hormones to the developing embryo, and the routes through which endocrine disrupting chemicals (EDCs) affect gonadal development in reptiles, especially turtles. Among EDCs, we focus on PCBs, BPA, pesticides like atrazine, nitrates, and heavy metals. We also consider whether adaptation might be possible in the face of persistent chemical insult and conclude that, while plausible, contemporary environmental change may outpace adaptive evolution, particularly for many species that are already endangered and suffer from small population sizes.
Topics: Animals; Boron Compounds; Endocrine Disruptors; Female; Male; Phenylalanine; Polychlorinated Biphenyls; Reptiles; Sex Determination Analysis; Sex Determination Processes; Turtles
PubMed: 27022970
DOI: 10.1159/000444770