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David Crews - One of the best experts on this subject based on the ideXlab platform.
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Analyzing the coordinated gene network underlying temperature-dependent Sex Determination in reptiles.
Seminars in cell & developmental biology, 2008Co-Authors: Christina M. Shoemaker, David CrewsAbstract:Although gonadogenesis has been extensively studied in vertebrates with genetic Sex Determination, investigations at the molecular level in nontraditional model organisms with temperature-dependent Sex Determination are relatively new areas of research. Results show that while the key players of the molecular network underlying gonad development appear to be retained, their functions range from conserved to novel roles. In this review, we summarize experiments investigating candidate molecular players underlying temperature-dependent Sex Determination. We discuss some of the problems encountered unraveling this network, pose potential solutions, and suggest rewarding future directions of research.
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gonadal expression of sf1 and aromatase during Sex Determination in the red eared slider turtle trachemys scripta a reptile with temperature dependent Sex Determination
Differentiation, 2007Co-Authors: Mary E Ramsey, Christina M. Shoemaker, David CrewsAbstract:Many egg-laying reptiles have temperature-dependent Sex Determination (TSD), where the offspring Sex is determined by incubation temperature during a temperature-sensitive period (TSP) in the middle third of development. The underlying mechanism transducing a temperature cue into an ovary or testis is unknown, but it is known that steroid hormones play an important role. During the TSP, exogenous application of estrogen can override a temperature cue and produce females, while blocking the activity of aromatase (Cyp19a1), the enzyme that converts testosterone to estradiol, produces males from a female-biased temperature. The production of estrogen is a key step in ovarian differentiation for many vertebrates, including TSD reptiles, and temperature-based differences in aromatase expression during the TSP may be a critical step in ovarian Determination. Steroidogenic factor-1 (Sf1) is a key gene in vertebrate Sex Determination and regulates many steroidogenic enzymes, including aromatase. We find that Sf1 and aromatase are differentially expressed during Sex Determination in the red-eared slider turtle, Trachemys scripta elegans. Sf1 is expressed at higher levels during testis development while aromatase expression increases during ovary Determination. We also assayed Sf1 and aromatase response to Sex-reversing treatments via temperature or the modulation of estrogen availability. Sf1 expression was redirected to low-level female-specific patterns with feminizing temperature shift or exogenous estradiol application and redirected to more intense male-specific patterns with male-producing temperature shift or inhibition of aromatase activity. Conversely, aromatase expression was redirected to more intense female-specific patterns with female-producing treatment and redirected toward diffuse low-level male-specific patterns with masculinizing Sex reversal. Our data do not lend support to a role for Sf1 in the regulation of aromatase expression during slider turtle Sex Determination, but do support a critical role for estrogen in ovarian development.
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steroid hormone induced male Sex Determination in an amniotic vertebrate
Journal of Experimental Zoology, 1992Co-Authors: Thane Wibbels, James J Bull, David CrewsAbstract:In many reptiles, Sex is determined by the temperature at which the eggs are incu- bated (i.e., temperature-dependent Sex Determination, or TSD). Past studies have shown that exoge- nous steroid hormones can override the effects of temperature and induce female Sex Determination. However, past attempts to induce male Sex Determination have consistently failed. In the present study, Sex Determination was studied in a turtle with TSD. By utilizing an incubation temperature regimen that resulted in approximately a 1:l Sex ratio in the control group, Sex Determination was shown to be sensitive to both exogenous androgen and estrogen treatments: androgen induced the production of male hatchlings, whereas estrogen induced the production of female hatchlings. This is the first report of an amniotic vertebrate in which an exogenous steroid hormone induces male Sex Determination. o 1992 Wiley-Liss, Inc. The mode of Sex Determination varies among rep- tiles and includes species with genotypic Sex deter- mination and others with temperature-dependent Sex Determination (TSD) (Bull, '80). Heteromorphic chromosomes have not been detected in reptiles with TSD and it is unknown if these species possess a genotypic Sex which is obscured by the effects of incubation temperature (Bull, '83). Past studies of reptiles with TSD have shown that administration of exogenous estrogens, and to a lesser extent tes- tosterone, can induce embryos to develop as females even if eggs are incubated at male-producing tem- peratures (reviewed by Raynaud and Pieau, 1985; also see Gutzke and Bull, '86; Bull et al., '88; Crews et al., '89, '91; Wibbels and Crews, '92). It has been suggested that the feminizing action of steroid hor- mones is estrogen-specific and that the effects of testosterone may be mediated via aromatization (Crews et al., '89). In these previous studies, however, steroid hormone treatments failed to induce the pro- duction of males from eggs incubated at female-pro- ducing temperatures. This suggests that steroid hormones are capable of driving Sex Determination only in the female direction. To address this hypothe- sis, we have incubated eggs of the red-eared slider turtle, kchemys scriptu, in a manner that produced a relatively equal proportion of male and female hatchlings in the control group. Other groups of eggs received either androgen or estrogen treatments.
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specificity of steroid hormone induced Sex Determination in a turtle
Journal of Endocrinology, 1992Co-Authors: Thane Wibbels, David CrewsAbstract:The specificity of steroid hormone-induced Sex Determination was investigated in the red-eared slider, Trachemys scripta, a turtle with temperature-dependent Sex Determination. All eggs were incubated at either a female-producing temperature (31 degrees C) or a male-producing temperature (26 degrees C) and received control or experimental treatments at stage 17-18 of embryonic development. A variety of treatments induced female Sex Determination at the male-producing temperature. Oestradiol-17 beta, diethylstilboestrol (DES) (an oestrogen agonist) and norethindrone (NET) (a progestin with reputed oestrogenic as well as anti-oestrogenic properties) were the most effective in inducing female Sex Determination. Other reputed oestrogen antagonists/partial agonists (i.e. tamoxifen, nafoxidine and clomiphene citrate) were also capable of inducing female Sex Determination, but to a lesser extent. A high dosage of testosterone resulted in the production of some females (7 of 15 hatchlings) whereas dihydrotestosterone had no detectable effect on Sex Determination. This latter finding suggests that testosterone could be acting via aromatization to oestradiol-17 beta. A few females resulted from eggs that had been treated with aromatase inhibitor, 1,4,6-androstatrien-3,17-dione (ATD) (3 of 97), the antiandrogen hydroxyflutamide (1 of 55) and progesterone (3 of 36), suggesting the possibilities of non-specific effects of these compounds when used in large dosages. Alternatively, metabolites of these compounds may be oestrogenic. Collectively, the results at the male-producing temperature are consistent with the hypothesis that steroid-induced female Sex Determination is mediated via an oestrogen-specific receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
François Le Galliard - One of the best experts on this subject based on the ideXlab platform.
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Some like it dry: Water restriction overrides heterogametic Sex Determination in two reptiles
Ecology and Evolution, 2019Co-Authors: Andréaz Dupoué, Olivier Lourdais, Sandrine Meylan, Francois Brischoux, Frédéric Angelier, David Rozen‐rechels, Yoan Marcangeli, Beatriz Decencière, Simon Agostini, François Le GalliardAbstract:The evolution of Sex Determination is complex and yet crucial in our understanding of population stability. In ectotherms, Sex Determination involves a variety of mechanisms including genetic Determination (GSD), environment Determination (ESD), but also interactions between the two via Sex reversal. In this study, we investigated whether water deprivation during pregnancy could override GSD in two heteroga-metic squamate reptiles. We demonstrated that water restriction in early gestation induced a male-biased secondary Sex ratio in both species, which could be explained by water Sex reversal as the more likely mechanism. We further monitored some long-term fitness estimates of offspring, which suggested that water Sex Determination (WSD) represented a compensatory strategy producing the rarest Sex according to Fisher's assumptions of frequency-dependent selection models. This study provides new insights into Sex Determination modes and calls for a general investigation of mechanisms behind WSD and to examine the evolutionary implications.
Andrew H Sinclair - One of the best experts on this subject based on the ideXlab platform.
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mammalian Sex Determination insights from humans and mice
Chromosome Research, 2012Co-Authors: Stefanie Eggers, Andrew H SinclairAbstract:Disorders of Sex development (DSD) are congenital conditions in which the development of chromosomal, gonadal, or anatomical Sex is atypical. Many of the genes required for gonad development have been identified by analysis of DSD patients. However, the use of knockout and transgenic mouse strains have contributed enormously to the study of gonad gene function and interactions within the development network. Although the genetic basis of mammalian Sex Determination and differentiation has advanced considerably in recent years, a majority of 46,XY gonadal dysgenesis patients still cannot be provided with an accurate diagnosis. Some of these unexplained DSD cases may be due to mutations in novel DSD genes or genomic rearrangements affecting regulatory regions that lead to atypical gene expression. Here, we review our current knowledge of mammalian Sex Determination drawing on insights from human DSD patients and mouse models.
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Sex Determination insights from the chicken
BioEssays, 2004Co-Authors: Craig A Smith, Andrew H SinclairAbstract:Not all vertebrates share the familiar system of XX:XY Sex Determination seen in mammals. In the chicken and other birds, Sex is determined by a ZZ:ZW Sex chromosome system. Gonadal development in the chicken has provided insights into the molecular genetics of vertebrate Sex Determination and how it has evolved. Such comparative studies show that vertebrate Sex-determining pathways comprise both conserved and divergent elements. The chicken embryo resembles lower vertebrates in that estrogens play a central role in gonadal Sex differentiation. However, several genes shown to be critical for mammalian Sex Determination are also expressed in the chicken, but their expression patterns differ, indicating functional plasticity. While the genetic trigger for Sex Determination in birds remains unknown, some promising candidate genes have recently emerged. The Z-linked gene, DMRT1, supports the Z-dosage model of avian Sex Determination. Two novel W-linked genes, ASW and FET1, represent candidate female determinants.
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A male-specific role for SOX9 in vertebrate Sex Determination
Development (Cambridge England), 1996Co-Authors: Jill Kent, Andrew H Sinclair, Susan C. Wheatley, Jane E. Andrews, Peter KoopmanAbstract:Mutation analyses of patients with campomelic dysplasia, a bone dysmorphology and XY Sex reversal syndrome, indicate that the SRY-related gene SOX9 is involved in both skeletal development and Sex Determination. To clarify the role SOX9 plays in vertebrate Sex Determination, we have investigated its expression during gonad development in mouse and chicken embryos. In the mouse, high levels of Sox9 mRNA were found in male (XY) but not female (XX) genital ridges, and were localised to the Sex cords of the developing testis. Purified fetal germ cells lacked Sox9 expression, indicating that Sox9 expression is specific to the Sertoli cell lineage. Sex specificity of SOX9 protein expression was confirmed using a polyclonal antiserum. The timing and cell-type specificity of Sox9 expression suggests that Sox9 may be directly regulated by SRY. Male-specific expression of cSOX9 mRNA during the Sex Determination period was also observed in chicken genital ridges. The conservation of Sexually dimorphic expression in two vertebrate classes which have significant differences in their Sex Determination mechanisms, points to a fundamental role for SOX9 in testis Determination in vertebrates. Sox9 expression was maintained in the mouse testis during fetal and adult life, but no expression was seen at any stage by in situ hybridisation in the developing ovary. Male-specific expression was also observed in the cells surrounding the Mullerian ducts and in the epididymis, and expression in both Sexes was detected in the developing collecting ducts of the metanephric kidney. These results suggest that SOX9 may have a wider role in the development of the genitourinary system.
L. Van De Zande - One of the best experts on this subject based on the ideXlab platform.
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a chimeric gene paternally instructs female Sex Determination in the haplodiploid wasp nasonia
Science, 2020Co-Authors: Yuan Zou, Leo W Beukeboom, Eveline C. Verhulst, Elzemiek Geuverink, L. Van De ZandeAbstract:Various primary signals direct insect Sex Determination. In hymenopteran insects, the presence of a paternal genome is needed to initiate female development. When absent, uniparental haploid males develop. We molecularly and functionally identified the instructor Sex-Determination gene, wasp overruler of masculinization (wom), of the haplodiploid wasp Nasonia vitripennis. This gene contains a P53-like domain coding region and arose by gene duplication and genomic rearrangements. Maternal silencing of wom results in male development of haploid embryos. Upon fertilization, early zygotic transcription from the paternal wom allele is initiated, followed by a timely zygotic expression of transformer (tra), leading to female development. Wom is an instructor gene with a parent-of-origin effect in Sex Determination.
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absence of complementary Sex Determination in the parasitoid wasp genus asobara hymenoptera braconidae
PLOS ONE, 2013Co-Authors: Bram Kuijper, Leo W Beukeboom, L. Van De Zande, Jetske G De Boer, Bregje Wertheim, Bart A PannebakkerAbstract:An attractive way to improve our understanding of Sex Determination evolution is to study the underlying mechanisms in closely related species and in a phylogenetic perspective. Hymenopterans are well suited owing to the diverse Sex Determination mechanisms, including different types of Complementary Sex Determination (CSD) and maternal control Sex Determination. We investigated different types of CSD in four species within the braconid wasp genus Asobara that exhibit diverse life-history traits. Nine to thirteen generations of inbreeding were monitored for diploid male production, brood size, offspring Sex ratio, and pupal mortality as indicators for CSD. In addition, simulation models were developed to compare these observations to predicted patterns for multilocus CSD with up to ten loci. The inbreeding regime did not result in diploid male production, decreased brood sizes, substantially increased offspring Sex ratios nor in increased pupal mortality. The simulations further allowed us to reject CSD with up to ten loci, which is a strong refutation of the multilocus CSD model. We discuss how the absence of CSD can be reconciled with the variation in life-history traits among Asobara species, and the ramifications for the phylogenetic distribution of Sex Determination mechanisms in the Hymenoptera.
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Genetics of Sex Determination in the haplodiploid wasp Nasonia vitripennis (Hymenoptera: Chalcidoidea).
Journal of genetics, 2010Co-Authors: Leo W Beukeboom, L. Van De ZandeAbstract:The parasitoid wasp Nasonia vitripennis reproduces by haplodiploidy; males are haploid and females are diploid. Sex Determination in Nasonia is not governed by complementary alleles at one or more Sex loci. As in most other insects, the Sex-determining pathway consists of the basal switch doubleSex that is Sex-specifically regulated by transformer. Analysis of a polyploid and a mutant gynandromorphic strain, suggested a parent-specific effect (imprinting) on Sex Determination in Nasonia. Zygotic activity of transformer is autoregulated and depends on a combination of maternal provision of tra mRNA and a paternal genome set. This constitutes a novel way of transformer control in insect Sex Determination implying maternal imprinting. The nature of the maternal imprint is not yet known and it remains to be determined how broadly the Nasonia Sex-determining mechanism applies to other haplodiploids.
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Maternal control of haplodiploid Sex Determination in the wasp Nasonia
Science (New York N.Y.), 2010Co-Authors: Eveline C. Verhulst, Leo W Beukeboom, L. Van De ZandeAbstract:All insects in the order Hymenoptera have haplodiploid Sex Determination, in which males emerge from haploid unfertilized eggs and females are diploid. Sex Determination in the honeybee Apis mellifera is controlled by the complementary Sex Determination (csd) locus, but the mechanisms controlling Sex Determination in other Hymenoptera without csd are unknown. We identified the Sex-Determination system of the parasitic wasp Nasonia, which has no csd locus. Instead, maternal input of Nasonia vitripennis transformer (Nvtra) messenger RNA, in combination with specific zygotic Nvtra transcription, in which Nvtra autoregulates female-specific splicing, is essential for female development. Our data indicate that males develop as a result of maternal imprinting that prevents zygotic transcription of the maternally derived Nvtra allele in unfertilized eggs. Upon fertilization, zygotic Nvtra transcription is initiated, which autoregulates the female-specific transcript, leading to female development.
Jetske G De Boer - One of the best experts on this subject based on the ideXlab platform.
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absence of complementary Sex Determination in the parasitoid wasp genus asobara hymenoptera braconidae
PLOS ONE, 2013Co-Authors: Bram Kuijper, Leo W Beukeboom, L. Van De Zande, Jetske G De Boer, Bregje Wertheim, Bart A PannebakkerAbstract:An attractive way to improve our understanding of Sex Determination evolution is to study the underlying mechanisms in closely related species and in a phylogenetic perspective. Hymenopterans are well suited owing to the diverse Sex Determination mechanisms, including different types of Complementary Sex Determination (CSD) and maternal control Sex Determination. We investigated different types of CSD in four species within the braconid wasp genus Asobara that exhibit diverse life-history traits. Nine to thirteen generations of inbreeding were monitored for diploid male production, brood size, offspring Sex ratio, and pupal mortality as indicators for CSD. In addition, simulation models were developed to compare these observations to predicted patterns for multilocus CSD with up to ten loci. The inbreeding regime did not result in diploid male production, decreased brood sizes, substantially increased offspring Sex ratios nor in increased pupal mortality. The simulations further allowed us to reject CSD with up to ten loci, which is a strong refutation of the multilocus CSD model. We discuss how the absence of CSD can be reconciled with the variation in life-history traits among Asobara species, and the ramifications for the phylogenetic distribution of Sex Determination mechanisms in the Hymenoptera.
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experimental support for multiple locus complementary Sex Determination in the parasitoid cotesia vestalis
Genetics, 2008Co-Authors: Jetske G De Boer, James B Whitfield, Aaron Rendahl, George E HeimpelAbstract:Despite its fundamental role in development, Sex Determination is highly diverse among animals. Approximately 20% of all animals are haplodiploid, with haploid males and diploid females. Haplodiploid species exhibit diverse but poorly understood mechanisms of Sex Determination. Some hymenopteran insect species exhibit single-locus complementary Sex Determination (sl-CSD), where heterozygosity at a polymorphic Sex locus initiates female development. Diploid males are homozygous at the Sex locus and represent a genetic load because they are inviable or sterile. Inbreeding depression associated with CSD is therefore expected to select for other modes of Sex Determination resulting in fewer or no diploid males. Here, we investigate an alternative, heretofore hypothetical, mode of Sex Determination: multiple-locus CSD (ml-CSD). Under ml-CSD, diploid males are predicted to develop only from zygotes that are homozygous at all Sex loci. We show that inbreeding for eight generations in the parasitoid wasp Cotesia vestalis leads to increasing proportions of diploid males, a pattern that is consistent with ml-CSD but not sl-CSD. The proportion of diploid males (0.27 ± 0.036) produced in the first generation of inbreeding (mother–son cross) suggests that two loci are likely involved. We also modeled diploid male production under CSD with three linked loci. Our data visually resemble CSD with linked loci because diploid male production in the second generation was lower than that in the first. To our knowledge, our data provide the first experimental support for ml-CSD.
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Sex Determination in the hymenoptera
Annual Review of Entomology, 2008Co-Authors: George E Heimpel, Jetske G De BoerAbstract:The dominant and ancestral mode of Sex Determination in the Hymenoptera is arrhenotokous parthenogenesis, in which diploid females develop from fertilized eggs and haploid males develop from unfertilized eggs. We discuss recent progress in the understanding of the genetic and cytoplasmic mechanisms that make arrhenotoky possible. The best-understood mode of Sex Determination in the Hymenoptera is complementary Sex Determination (CSD), in which diploid males are produced under conditions of inbreeding. The gene mediating CSD has recently been cloned in the honey bee and has been named the complementary Sex determiner. However, CSD is only known from 4 of 21 hymenopteran superfamilies, with some taxa showing clear evidence of the absence of CSD. Sex Determination in the model hymenopteran Nasonia vitripennis does not involve CSD, but it is consistent with a form of genomic imprinting in which activation of the female developmental pathway requires paternally derived genes. Some other hymenopterans are not arrhenotokous but instead exhibit thelytoky or paternal genome elimination.
