451
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Kopp A. Dmrt genes in the development and evolution of sexual dimorphism. Trends Genet 2012; 28:175-84. [PMID: 22425532 DOI: 10.1016/j.tig.2012.02.002] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 02/07/2012] [Accepted: 02/08/2012] [Indexed: 12/20/2022]
Abstract
Most animals are sexually dimorphic, but different taxa have different sex-specific traits. Despite major differences in the genetic control of sexual development among animal lineages, the doublesex/mab-3 related (Dmrt) family of transcription factors has been shown to be involved in sex-specific differentiation in all animals that have been studied. In recent years the functions of Dmrt genes have been characterized in many animal groups, opening the way to a broad comparative perspective. This review focuses on the similarities and differences in the functions of Dmrt genes across the animal kingdom. I highlight a number of common themes in the sexual development of different taxa, discuss how Dmrt genes have acquired new roles during animal evolution, and show how they have contributed to the origin of novel sex-specific traits.
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Affiliation(s)
- Artyom Kopp
- Department of Evolution and Ecology, University of California-Davis, Davis, CA 95616 USA.
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452
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Abozaid H, Wessels S, Hörstgen-Schwark G. Elevated Temperature Applied during Gonadal Transformation Leads to Male Bias in Zebrafish (Danio rerio). Sex Dev 2012; 6:201-9. [DOI: 10.1159/000336297] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2011] [Indexed: 11/19/2022] Open
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453
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Ventura T, Manor R, Aflalo ED, Weil S, Rosen O, Sagi A. Timing Sexual Differentiation: Full Functional Sex Reversal Achieved Through Silencing of a Single Insulin-Like Gene in the Prawn, Macrobrachium rosenbergii1. Biol Reprod 2012; 86:90. [DOI: 10.1095/biolreprod.111.097261] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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454
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Angelopoulou R, Lavranos G, Manolakou P. Sex determination strategies in 2012: towards a common regulatory model? Reprod Biol Endocrinol 2012; 10:13. [PMID: 22357269 PMCID: PMC3311596 DOI: 10.1186/1477-7827-10-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Accepted: 02/22/2012] [Indexed: 12/21/2022] Open
Abstract
Sex determination is a complicated process involving large-scale modifications in gene expression affecting virtually every tissue in the body. Although the evolutionary origin of sex remains controversial, there is little doubt that it has developed as a process of optimizing metabolic control, as well as developmental and reproductive functions within a given setting of limited resources and environmental pressure. Evidence from various model organisms supports the view that sex determination may occur as a result of direct environmental induction or genetic regulation. The first process has been well documented in reptiles and fish, while the second is the classic case for avian species and mammals. Both of the latter have developed a variety of sex-specific/sex-related genes, which ultimately form a complete chromosome pair (sex chromosomes/gonosomes). Interestingly, combinations of environmental and genetic mechanisms have been described among different classes of animals, thus rendering the possibility of a unidirectional continuous evolutionary process from the one type of mechanism to the other unlikely. On the other hand, common elements appear throughout the animal kingdom, with regard to a) conserved key genes and b) a central role of sex steroid control as a prerequisite for ultimately normal sex differentiation. Studies in invertebrates also indicate a role of epigenetic chromatin modification, particularly with regard to alternative splicing options. This review summarizes current evidence from research in this hot field and signifies the need for further study of both normal hormonal regulators of sexual phenotype and patterns of environmental disruption.
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Affiliation(s)
- Roxani Angelopoulou
- Experimental Embryology Unit, Department of Histology and Embryology, Medical School, Athens University, Athens, Greece
| | - Giagkos Lavranos
- Experimental Embryology Unit, Department of Histology and Embryology, Medical School, Athens University, Athens, Greece
| | - Panagiota Manolakou
- Experimental Embryology Unit, Department of Histology and Embryology, Medical School, Athens University, Athens, Greece
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455
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A Y-linked anti-Müllerian hormone duplication takes over a critical role in sex determination. Proc Natl Acad Sci U S A 2012; 109:2955-9. [PMID: 22323585 DOI: 10.1073/pnas.1018392109] [Citation(s) in RCA: 313] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Gonadal sex determination in vertebrates generally follows a sequence of genetically programmed events. In what is seemingly becoming a pattern, all confirmed or current candidate "master" sex-determining genes reported in this group, e.g., SRY in eutherian mammals, DMY/dmrt1bY in medaka, DM-W in the African clawed frog, and DMRT1 in chicken encode transcription factors. In contrast, here we show that a male-specific, duplicated copy of the anti-Müllerian hormone (amh) is implicated in testicular development of the teleost fish Patagonian pejerrey (Odontesthes hatcheri). The gene, termed amhy because it is found in a single metacentric/submetacentric chromosome of XY individuals, is expressed much earlier than the autosomal amh (6 d after fertilization vs. 12 wk after fertilization) and is localized to presumptive Sertoli cells of XY males during testicular differentiation. Moreover, amhy knockdown in XY embryos resulted in the up-regulation of foxl2 and cyp19a1a mRNAs and the development of ovaries. These results are evidence of a functional amh duplication in vertebrates and suggest that amhy may be the master sex-determining gene in this species. If confirmed, this would be a unique instance of a hormone-related gene, a member of the TGF-β superfamily, in such a role.
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456
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Matson CK, Zarkower D. Sex and the singular DM domain: insights into sexual regulation, evolution and plasticity. Nat Rev Genet 2012; 13:163-74. [PMID: 22310892 PMCID: PMC3595575 DOI: 10.1038/nrg3161] [Citation(s) in RCA: 263] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Most animals reproduce sexually, but the genetic and molecular mechanisms that determine the eventual sex of each embryo vary remarkably. DM domain genes, which are related to the insect gene doublesex, are integral to sexual development and its evolution in many metazoans. Recent studies of DM domain genes reveal mechanisms by which new sexual dimorphisms have evolved in invertebrates and show that one gene, Dmrt1, was central to multiple evolutionary transitions between sex-determining mechanisms in vertebrates. In addition, Dmrt1 coordinates a surprising array of distinct cell fate decisions in the mammalian gonad and even guards against transdifferentiation of male cells into female cells in the adult testis.
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Affiliation(s)
- Clinton K Matson
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, Minnesota 55455, USA
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457
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Wu GC, Chiu PC, Lin CJ, Lyu YS, Lan DS, Chang CF. Testicular dmrt1 Is Involved in the Sexual Fate of the Ovotestis in the Protandrous Black Porgy1. Biol Reprod 2012; 86:41. [DOI: 10.1095/biolreprod.111.095695] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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458
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459
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460
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461
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Abstract
Although sex chromosomes have been the focus of a great deal of scientific scrutiny, most interest has centred on understanding the evolution and relative importance of X and Z chromosomes. By contrast, the sex-limited W and Y chromosomes have received far less attention, both because of their generally degenerate nature and the difficulty in studying non-recombining and often highly heterochromatic genomic regions. However, recent theory and empirical evidence suggest that the W and Y chromosomes play a far more important role in sex-specific fitness traits than would be expected based on their size alone, and this importance may explain the persistence of some Y and W chromosomes in the face of powerful degradative forces. In addition to their role in fertility and fecundity, the sex-limited nature of these genomic regions results in unique evolutionary forces acting on Y and W chromosomes, implicating them as potentially major contributors to sexual selection and speciation. Recent empirical studies have borne out these predictions and revealed that some W and Y chromosomes play a vital role in key sex-specific evolutionary processes.
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Affiliation(s)
- Judith E Mank
- Department of Zoology, Edward Grey Institute, University of Oxford, South Parks Road, Oxford, UK.
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462
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Dmrt1 mutation causes a male-to-female sex reversal after the sex determination by Dmy in the medaka. Chromosome Res 2011; 20:163-76. [DOI: 10.1007/s10577-011-9264-x] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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463
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464
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465
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Clinton M, Zhao D, Nandi S, McBride D. Evidence for avian cell autonomous sex identity (CASI) and implications for the sex-determination process? Chromosome Res 2011; 20:177-90. [DOI: 10.1007/s10577-011-9257-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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466
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Livernois AM, Graves JAM, Waters PD. The origin and evolution of vertebrate sex chromosomes and dosage compensation. Heredity (Edinb) 2011; 108:50-8. [PMID: 22086077 DOI: 10.1038/hdy.2011.106] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In mammals, birds, snakes and many lizards and fish, sex is determined genetically (either male XY heterogamy or female ZW heterogamy), whereas in alligators, and in many reptiles and turtles, the temperature at which eggs are incubated determines sex. Evidently, different sex-determining systems (and sex chromosome pairs) have evolved independently in different vertebrate lineages. Homology shared by Xs and Ys (and Zs and Ws) within species demonstrates that differentiated sex chromosomes were once homologous, and that the sex-specific non-recombining Y (or W) was progressively degraded. Consequently, genes are left in single copy in the heterogametic sex, which results in an imbalance of the dosage of genes on the sex chromosomes between the sexes, and also relative to the autosomes. Dosage compensation has evolved in diverse species to compensate for these dose differences, with the stringency of compensation apparently differing greatly between lineages, perhaps reflecting the concentration of genes on the original autosome pair that required dosage compensation. We discuss the organization and evolution of amniote sex chromosomes, and hypothesize that dosage insensitivity might predispose an autosome to evolving function as a sex chromosome.
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Affiliation(s)
- A M Livernois
- Evolution Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
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467
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Yilmaz A, Tepeli C, Garip M, Caglayan T. The effects of incubation temperature on the sex of Japanese quail chicks. Poult Sci 2011; 90:2402-6. [PMID: 21934026 DOI: 10.3382/ps.2011-01471] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The effects of incubation temperature on the sex of Japanese quail chicks were investigated in this study. The study was conducted on Japanese quail. In all, 4500 eggs obtained from 2 generations were used. At the beginning of the study, a new flock was formed from available hatching eggs. Hatching eggs were gathered at 3 different ages (8 to 10 weeks, 16 to 18 weeks and 22 to 24 weeks of age) from the laying period in this flock. These eggs were exposed to 5 different incubation temperatures (36.7, 37.2, 37.7, 38.2, and 38.7°C). The hatching results were evaluated for each group. Chicks obtained from these temperature groups were reared separately to obtain quail for breeding. Eggs for incubation were gathered from these breeding quail when they were between 15 and 18 weeks of age. These eggs were placed in an incubator at a standard (37.7°C) temperature, separated by F(1)-generation temperature groups. The chicks in all groups were reared separately, and the sex of the chicks was determined at maturity. Statistical differences (P < 0.05) were found for the sex of the chicks in the third group (22 to 24 weeks) of the F(1) generation, compared with other groups. This result confirmed the hypothesis that different incubation temperatures for the first generation (at the embryo stage) might influence the sex of the next generation of chicks. Further studies are needed to investigate the effects of incubation temperature on chicks from different perspectives.
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Affiliation(s)
- A Yilmaz
- Department of Animal Science, University of Selcuk, Selçuklu, Konya, Turkey.
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468
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Characterisation and comparison of the chicken H1 RNA polymerase III promoter for short hairpin RNA expression. Biochem Biophys Res Commun 2011; 416:194-8. [PMID: 22093828 DOI: 10.1016/j.bbrc.2011.11.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 11/04/2011] [Indexed: 12/28/2022]
Abstract
The U6 and 7SK RNA polymerase III promoters are widely used in RNAi research for the expression of shRNAs. However, with their increasing use in vitro and in vivo, issues associated with cytotoxicity have become apparent with their use. Therefore, alternative promoters such as the weaker H1 promoter are becoming a popular choice. With interest in the chicken as a model organism, we aimed to identify and characterise the chicken H1 promoter for the expression of shRNAs for the purpose of RNAi. The chicken H1 promoter was isolated and sequence analysis identified conserved RNA polymerase III promoter elements. A shRNA expression cassette containing the chicken H1 promoter and shRNA targeting enhanced green fluorescent protein (EGFP) was developed. An RNAse protection assay confirmed activity of the promoter determined by the detection of expressed shRNAs. Comparison of the H1 promoter to the chicken RNA polymerase III 7SK and U6 promoters demonstrated that expressed shRNAs from the H1 promoter induced gene specific silencing, albeit to lower levels in comparison to both 7SK and U6 promoters. Here we have identified a new tool for RNAi research with specific applications to the chicken. The availability of a RNA polymerase III promoter that drives shRNA expression to reduced levels will greatly benefit in ovo/in vivo applications where there are concerns of cytotoxicity resulting from overexpression of an shRNA.
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469
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Post-transcriptional gene silencing by RNA interference in non-mammalian vertebrate systems: Where do we stand? MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2011; 728:158-71. [DOI: 10.1016/j.mrrev.2011.09.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Revised: 09/02/2011] [Accepted: 09/06/2011] [Indexed: 12/20/2022]
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470
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Sarre SD, Ezaz T, Georges A. Transitions between sex-determining systems in reptiles and amphibians. Annu Rev Genomics Hum Genet 2011; 12:391-406. [PMID: 21801024 DOI: 10.1146/annurev-genom-082410-101518] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Important technological advances in genomics are driving a new understanding of the evolution of sex determination in vertebrates. In particular, comparative chromosome mapping in reptiles has shown an intriguing distribution of homology in sex chromosomes across reptile groups. When this new understanding is combined with the widespread distribution of genetic and temperature-dependent sex-determination mechanisms among reptiles, it is apparent that transitions between modes have occurred many times, as they have for amphibians (particularly between male and female heterogamety). It is also likely that thermosensitivity in sex determination is a key factor in those transitions in reptiles, and possibly in amphibians too. New models of sex determination involving temperature thresholds are providing the framework for the investigation of transitions and making possible key predictions about the homologies and sex-determination patterns expected among taxa in these groups. Molecular cytogenetics and other genomic approaches are essential to providing the fundamental material necessary to make advances in this field.
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Affiliation(s)
- Stephen D Sarre
- Wildlife Genetics Laboratory, Institute for Applied Ecology, University of Canberra, ACT 2601, Australia.
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471
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Abstract
Gonadal cellular organization is very similar in all vertebrates, though different processes can trigger bipotential gonads to develop into either testes or ovaries. While mammals and birds, apart from some exceptions, show genetic sex determination (GSD), other animals, like turtles and crocodiles, express temperature-dependent sex determination. In some groups of animals, GSD can also be overridden by hormone or temperature influences, indicating how fragile this system can be. This review aims to explain the fundamental molecular mechanisms involved in mammalian GSD, mainly referring to mouse as a major model. Conceivably, other mammals might show a molecular mechanism different from the commonly investigated murine species.
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Affiliation(s)
- P Parma
- Department of Animal Science, Agricultural Faculty of Science, Milan University, Milan, Italy.
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472
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Uller T, Helanterä H. From the origin of sex-determining factors to the evolution of sex-determining systems. QUARTERLY REVIEW OF BIOLOGY 2011; 86:163-80. [PMID: 21954700 DOI: 10.1086/661118] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sex determination is typically classified as either genotypic or environmental. However, this dichotomy obscures the developmental origin and evolutionary modification of determinants of sex, and therefore hinders an understanding of the processes that generates diversity in sex-determining systems. Recent research on reptiles and fish emphasizes that sex determination is a multifactorial regulatory process that is best understood as a threshold dichotomy rather than as the result of genetically inherited triggers of development. Here we critically assess the relationship between the developmental origin of sex-determining factors and evolutionary transitions in sex-determining systems. Our perspective emphasizes the importance of both genetic and nongenetic causes in evolution of sex determination and may help to generate predictions with respect to the evolutionary patterns of sex-determining systems and the underlying diversity of developmental and genetic regulatory networks.
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Affiliation(s)
- Tobias Uller
- Edward Grey Institute, Department of Zoology, University of Oxford Oxford OX1 3PS United Kingdom.
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473
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Chromosomal evolution in Gekkonidae. I. Chromosome painting between Gekko and Hemidactylus species reveals phylogenetic relationships within the group. Chromosome Res 2011; 19:843-55. [PMID: 21987185 DOI: 10.1007/s10577-011-9241-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 09/05/2011] [Accepted: 09/05/2011] [Indexed: 10/17/2022]
Abstract
Geckos are a large group of lizards characterized by a rich variety of species, different modes of sex determination and diverse karyotypes. In spite of many unresolved questions on lizards' phylogeny and taxonomy, the karyotypes of most geckos have been studied by conventional cytogenetic methods only. We used flow-sorted chromosome-specific painting probes of Japanese gecko (Gekko japonicus), Mediterranean house gecko (Hemidactylus turcicus) and flat-tailed house gecko (Hemidactylus platyurus) to reveal homologous regions and to study karyotype evolution in seven gecko species (Gekko gecko, G. japonicus, G. ulikovskii, G. vittatus, Hemidactylus frenatus, H. platyurus and H. turcicus). Generally, the karyotypes of geckos were found to be conserved, but we revealed some characteristic rearrangements including both fissions and fusions in Hemidactylus. The karyotype of H. platyurus contained a heteromorphic pair in all female individuals, where one of the homologues had a terminal DAPI-negative and C-positive heterochromatic block that might indicate a putative sex chromosome. Among two male individuals studied, only one carried such a polymorphism, and the second one had none, suggesting a possible ZZ/ZW sex determination in some populations of this species. We found that all Gekko species have retained the putative ancestral karyotype, whilst the fission of the largest ancestral chromosome occurred in the ancestor of modern Hemidactylus species. Three common fissions occurred in the ancestor of Mediterranean house and flat-tailed house geckos, suggesting their sister group relationships. PCR-assisted mapping on flow-sorted chromosome libraries with conserved DMRT1 gene primers in G. japonicus indicates the localization of DMRT1 gene on chromosome 6.
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474
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Díaz-Hernández V, Marmolejo-Valencia A, Harfush M, Merchant-Larios H. Formation of the genital ridges is preceded by a domain of ectopic Sox9-expressing cells in Lepidochelys olivacea. Dev Biol 2011; 361:156-66. [PMID: 22008791 DOI: 10.1016/j.ydbio.2011.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Revised: 09/22/2011] [Accepted: 10/01/2011] [Indexed: 11/16/2022]
Abstract
Bipotential gonads represent the structural framework from which alternative molecular sex determination networks have evolved. Maintenance of Sox9 expression in Sertoli cells is required for the structural and functional integrity of male gonads in mammals and probably in most amniote vertebrates. However, spatial and temporal patterns of Sox9 expression have diversified along evolution. Species with temperature sex determination are an interesting predictive model since one of two alternative developmental outcomes, either ovary or testis occurs under controlled laboratory conditions. In the sea turtle Lepidochelys olivacea, Sox9 is expressed in the medullary cords of bipotential gonads when incubated at both female- or male-promoting temperature (FT or MT). Sox9 is then turned off in presumptive ovaries, while it remains turned on in testes. In the current study, Sox9 was used as a marker of the medullary cell lineage to investigate if the medullary cords originate from mesothelial cells at the genital ridges where Sox9 is upregulated, or, if they derive from a cell population specified at an earlier developmental stage, which maintains Sox9 expression. Using immunofluorescence and in situ hybridization, embryos were analyzed prior to, during and after gonadal sex determination. A T-shaped domain (T-Dom) formed by cytokeratin (CK), N-cadherin (Ncad) and SOX9-expressing cells was found at the upper part of the hindgut dorsal mesentery. The arms of the T-Dom were extended to both sides towards the ventromedial mesonephric ridge before the thickening of the genital ridges, indicating that they contained gonadal epithelial cell precursors. Thereafter, expression of Sox9 was maintained in medullary cords while it was downregulated at the surface epithelium of bipotential gonads in both FT and MT. This result contrasts with observations in mammals and birds, in which Sox9 upregulation starts at a later stage in the inner cells underlying the Sox9-negative surface epithelium, suggesting that the establishment of a self-regulatory Sox9 loop required for Sertoli cell determination has evolved. The T-shaped domain at the upper part of the hindgut dorsal mesentery found in the current study may represent the earliest precursor of the genital ridges, previously unnoticed in amniote vertebrates.
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475
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Carré GA, Couty I, Hennequet-Antier C, Govoroun MS. Gene expression profiling reveals new potential players of gonad differentiation in the chicken embryo. PLoS One 2011; 6:e23959. [PMID: 21931629 PMCID: PMC3170287 DOI: 10.1371/journal.pone.0023959] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 08/02/2011] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND In birds as in mammals, a genetic switch determines whether the undifferentiated gonad develops into an ovary or a testis. However, understanding of the molecular pathway(s) involved in gonad differentiation is still incomplete. METHODOLOGY/PRINCIPAL FINDINGS With the aim of improving characterization of the molecular pathway(s) involved in gonad differentiation in the chicken embryo, we developed a large scale real time reverse transcription polymerase chain reaction approach on 110 selected genes for evaluation of their expression profiles during chicken gonad differentiation between days 5.5 and 19 of incubation. Hierarchical clustering analysis of the resulting datasets discriminated gene clusters expressed preferentially in the ovary or the testis, and/or at early or later periods of embryonic gonad development. Fitting a linear model and testing the comparisons of interest allowed the identification of new potential actors of gonad differentiation, such as Z-linked ADAMTS12, LOC427192 (corresponding to NIM1 protein) and CFC1, that are upregulated in the developing testis, and BMP3 and Z-linked ADAMTSL1, that are preferentially expressed in the developing ovary. Interestingly, the expression patterns of several members of the transforming growth factor β family were sexually dimorphic, with inhibin subunits upregulated in the testis, and bone morphogenetic protein subfamily members including BMP2, BMP3, BMP4 and BMP7, upregulated in the ovary. This study also highlighted several genes displaying asymmetric expression profiles such as GREM1 and BMP3 that are potentially involved in different aspects of gonad left-right asymmetry. CONCLUSION/SIGNIFICANCE This study supports the overall conservation of vertebrate sex differentiation pathways but also reveals some particular feature of gene expression patterns during gonad development in the chicken. In particular, our study revealed new candidate genes which may be potential actors of chicken gonad differentiation and provides evidence of the preferential expression of BMPs in the developing ovary and Inhibin/Activin subunits in the developing testis.
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Affiliation(s)
- Gwenn-Aël Carré
- Physiologie de la Reproduction et des Comportements UMR 6175, INRA- CNRS-Université F. Rabelais de Tours-Haras Nationaux, Nouzilly, France
| | - Isabelle Couty
- Physiologie de la Reproduction et des Comportements UMR 6175, INRA- CNRS-Université F. Rabelais de Tours-Haras Nationaux, Nouzilly, France
| | | | - Marina S. Govoroun
- Physiologie de la Reproduction et des Comportements UMR 6175, INRA- CNRS-Université F. Rabelais de Tours-Haras Nationaux, Nouzilly, France
- * E-mail:
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476
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Abstract
Neo-sex chromosomes often originate from sex chromosome-autosome fusions and constitute an important basis for the study of gene degeneration and expression in a sex chromosomal context. Neo-sex chromosomes are known from many animal and plant lineages, but have not been reported in birds, a group in which genome organization seems particularly stable. Following indications of sex linkage and unexpected sex-biased gene expression in warblers (Sylvioidea; Passeriformes), we have conducted an extensive marker analysis targeting 31 orthologues of loci on zebra finch chromosome 4a in five species, representative of independent branches of Passerida. We identified a region of sex linkage covering approximately the first half (10 Mb) of chromosome 4a, and associated to both Z and W chromosomes, in three Sylvioidea passerine species. Linkage analysis in an extended pedigree of one species additionally confirmed the association between this part of chromosome 4a and the Z chromosome. Markers located between 10 and 21 Mb of chromosome 4a showed no signs of sex linkage, suggesting that only half of the chromosome was involved in this transition. No sex linkage was observed in non-Sylvioidea passerines, indicating that the neo-sex chromosome arose at the base of the Sylvioidea branch of the avian phylogeny, at 47.4-37.6 millions years ago (MYA), substantially later than the ancestral sex chromosomes (150 MYA). We hypothesize that the gene content of chromosome 4a might be relevant in its transition to a sex chromosome, based on the presence of genes (for example, the androgen receptor) that could offer a selective advantage when associated to Z-linked sex determination loci.
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477
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DMRT1 prevents female reprogramming in the postnatal mammalian testis. Nature 2011; 476:101-4. [PMID: 21775990 PMCID: PMC3150961 DOI: 10.1038/nature10239] [Citation(s) in RCA: 409] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 05/27/2011] [Indexed: 01/06/2023]
Abstract
Sex in mammals is determined in the foetal gonad by the presence or absence of the Y chromosome gene Sry, which controls whether bipotential precursor cells differentiate into testicular Sertoli cells or ovarian granulosa cells1. This pivotal decision in a single gonadal cell type ultimately controls sexual differentiation throughout the body. Sex determination can be viewed as a battle for primacy in the foetal gonad between a male regulatory gene network in which Sry activates Sox9 and a female network involving Wnt/β-catenin signaling (Supplemental Fig. 1)2. In females the primary sex-determining decision is not final: loss of the FOXL2 transcription factor in adult granulosa cells can reprogramme granulosa cells into Sertoli cells2. Here we show that sexual fate is also surprisingly labile in the testis: loss of the DMRT1 transcription factor3 in mouse Sertoli cells, even in adults, activates Foxl2 and reprogrammes Sertoli cells into granulosa cells. In this environment, theca cells form, oestrogen is produced, and germ cells appear feminized. Thus Dmrt1 is essential to maintain mammalian testis determination, and competing regulatory networks maintain gonadal sex long after the foetal choice between male and female. Dmrt1 and Foxl2 are conserved throughout vertebrates4,5 and Dmrt1-related sexual regulators are conserved throughout metazoans3. Antagonism between Dmrt1 and Foxl2 for control of gonadal sex may therefore extend beyond mammals. Reprogramming due to loss of Dmrt1 also may help explain the etiology of human syndromes linked to DMRT1, including disorders of sexual differentiation6 and testicular cancer7.
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478
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Arnold AP, Itoh Y. Factors causing sex differences in birds. AVIAN BIOLOGY RESEARCH 2011; 4:10.3184/175815511X13070045977959. [PMID: 24353746 PMCID: PMC3864897 DOI: 10.3184/175815511x13070045977959] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In recent years, increasing evidence suggests that sex differences in the phenotype of all tissues is influenced by the inequality of effects of sex chromosome genes in the two sexes. In birds, genes on the Z chromosome are not well dosage compensated, so that most Z genes are expressed higher in ZZ male cells than in ZW female cells. The sex difference in expression of Z and W genes is likely to cause sex differences within cells, in addition to the sex differences caused by different levels of testicular and ovarian hormones. The sexual imbalance in cell physiology has implications for aviculture and novel developments in the poultry industry.
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Affiliation(s)
- Arthur P Arnold
- Department of integrative Biology & Physiology University of California, Los Angeles
| | - Yuichiro Itoh
- Department of integrative Biology & Physiology University of California, Los Angeles
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479
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An SNP-Based Linkage Map for Zebrafish Reveals Sex Determination Loci. G3-GENES GENOMES GENETICS 2011; 1:3-9. [PMID: 21949597 PMCID: PMC3178105 DOI: 10.1534/g3.111.000190] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A surprising diversity of mechanisms controls sex determination of vertebrate organisms, even among closely related species. Both genetic and temperature-dependent systems of sex determination have been described in teleost fish. In the common zebrafish model organism, heteromorphic sex chromosomes are not observed, and the potential role of a genetic component of sex determination remains largely unknown. Here we report a genome-wide linkage study of sex determination in zebrafish using a novel SNP genetic map. We identified loci on zebrafish chromosomes 5 (LOD score 7.9) and 16 (LOD score 9.3) governing sex determination as a complex trait, rather than as an XY or ZW genetic system. Each of these loci contains a prominent candidate gene with a conserved role in sex determination across additional species that suggest potential mechanisms of sex determination in zebrafish. The chromosome 5 locus harbors dmrt1, a key gene in sex determination from fruit flies to humans; mutation of the human DMRT1 ortholog is a cause of complete sex reversal of XY individuals. The chromosome 16 locus harbors cyp21a2; mutation of the human CYP21A2 ortholog is one of the more common causes of pseudohermaphroditism. Mutation detection at each of these candidate genes within the zebrafish cross identified hypomorphic variants on the female-associated allele of each locus. The two loci together accounted for 16% of variance of the trait. Interacting environmental cues are likely to be an additional important component of sex determination in zebrafish.
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480
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Krentz AD, Murphy MW, Sarver AL, Griswold MD, Bardwell VJ, Zarkower D. DMRT1 promotes oogenesis by transcriptional activation of Stra8 in the mammalian fetal ovary. Dev Biol 2011; 356:63-70. [PMID: 21621532 DOI: 10.1016/j.ydbio.2011.05.658] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 04/11/2011] [Accepted: 05/13/2011] [Indexed: 01/05/2023]
Abstract
Dmrt1 belongs to the DM domain gene family of conserved sexual regulators. In the mouse Dmrt1 is expressed in the genital ridge (the gonadal primordium) in both sexes and then becomes testis-specific shortly after sex determination. The essential role of DMRT1 in testicular differentiation is well established, and includes transcriptional repression of the meiotic inducer Stra8. However Dmrt1 mutant females are fertile and the role of Dmrt1 in the ovary has not been studied. Here we show in the mouse that most Dmrt1 mutant germ cells in the fetal ovary have greatly reduced expression of STRA8, and fail to properly localize SYCP3 and γH2AX during meiotic prophase. Lack of DMRT1 in the fetal ovary results in the formation of many fewer primordial follicles in the juvenile ovary, although these are sufficient for fertility. Genome-wide chromatin immunoprecipitiation (ChIP-chip) and quantitative ChIP (qChIP) combined with mRNA expression profiling suggests that transcriptional activation of Stra8 in fetal germ cells is the main function of DMRT1 in females, and that this regulation likely is direct. Thus DMRT1 controls Stra8 sex-specifically, activating it in the fetal ovary and repressing it in the adult testis.
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Affiliation(s)
- Anthony D Krentz
- Dept. of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, USA
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481
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Mank JE, Hosken DJ, Wedell N. Some inconvenient truths about sex chromosome dosage compensation and the potential role of sexual conflict. Evolution 2011; 65:2133-44. [PMID: 21790564 DOI: 10.1111/j.1558-5646.2011.01316.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Sex chromosome dosage compensation was once thought to be required to balance gene expression levels between sex-linked and autosomal genes in the heterogametic sex. Recent evidence from a range of animals has indicated that although sex chromosome dosage compensation exists in some clades, it is far from a necessary companion to sex chromosome evolution, and is in fact rather rare in animals. This raises questions about why complex dosage compensation mechanisms arise in some clades when they are not strictly needed, and suggests that the role of sex-specific selection in sex chromosome gene regulation should be reassessed. We show there exists a tremendous diversity in the mechanisms that regulate gene dosage and argue that sexual conflict may be an overlooked agent responsible for some of the variation seen in sex chromosome gene dose regulation.
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Affiliation(s)
- Judith E Mank
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford OX1 3PS, UK.
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482
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Ogino Y, Miyagawa S, Katoh H, Prins GS, Iguchi T, Yamada G. Essential functions of androgen signaling emerged through the developmental analysis of vertebrate sex characteristics. Evol Dev 2011; 13:315-25. [DOI: 10.1111/j.1525-142x.2011.00482.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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483
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Complex Chromosome Rearrangement 46,XY, der(9)t(Y;9)(q12;p23) in a Girl With Sex Reversal and Mental Retardation. Urology 2011; 77:1213-6. [DOI: 10.1016/j.urology.2010.07.473] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 07/06/2010] [Accepted: 07/20/2010] [Indexed: 12/11/2022]
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484
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Silber S, Geisler JH, Bolortsetseg M. Unexpected resilience of species with temperature-dependent sex determination at the Cretaceous-Palaeogene boundary. Biol Lett 2011; 7:295-8. [PMID: 20980293 PMCID: PMC3061185 DOI: 10.1098/rsbl.2010.0882] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 10/07/2010] [Indexed: 11/12/2022] Open
Abstract
It has been suggested that climate change at the Cretaceous-Palaeogene (K-Pg) boundary, initiated by a bolide impact or volcanic eruptions, caused species with temperature-dependent sex determination (TSD), including dinosaurs, to go extinct because of a skewed sex ratio towards all males. To test this hypothesis, the sex-determining mechanisms (SDMs) of Cretaceous tetrapods of the Hell Creek Formation (Montana, USA) were inferred using parsimony optimizations of SDMs on a tree, including Hell Creek species and their extant relatives. Although the SDMs of non-avian dinosaurs could not be inferred, we were able to determine the SDMs of 62 species; 46 had genotypic sex determination (GSD) and 16 had TSD. The TSD hypothesis for extinctions performed poorly, predicting between 32 and 34 per cent of survivals and extinctions. Most surprisingly, of the 16 species with TSD, 14 of them survived into the Early Palaeocene. In contrast, 61 per cent of species with GSD went extinct. Possible explanations include minimal climate change at the K-Pg, or if climate change did occur, TSD species that survived had egg-laying behaviour that prevented the skewing of sex ratios, or had a sex ratio skewed towards female rather than male preponderance. Application of molecular clocks may allow the SDMs of non-avian dinosaurs to be inferred, which would be an important test of the pattern discovered here.
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Affiliation(s)
- Sherman Silber
- Infertility Center of Saint Louis, St Luke's Hospital, Saint Louis, MO 63017, USA.
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485
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Abstract
Karten's neocortex hypothesis holds that many component cell populations of the sauropsid dorsal ventricular ridge (DVR) are homologous to particular cell populations in layers of auditory and visual tectofugal-recipient neocortex of mammals (i.e., temporal neocortex), as well as to some amygdaloid populations. The claustroamygdalar hypothesis, based on gene expression domains, proposes that mammalian homologues of DVR are found in the claustrum, endopiriform nuclei, and/or pallial amygdala. Because hypotheses of homology need to account for the totality of the evidence, the available data on multiple forebrain features of sauropsids and mammals are reviewed here. While some genetic data are compatible with the claustroamygdalar hypothesis, and developmental (epigenetic) data are indecisive, hodological, morphological, and topographical data favor the neocortex hypothesis and are inconsistent with the claustroamygdalar hypothesis. Detailed studies of gene signaling cascades that establish neuronal cell-type identity in DVR, tectofugal-recipient neocortex, and claustroamygdala will be needed to resolve this debate about the evolution of neocortex.
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Affiliation(s)
- Ann B Butler
- Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, USA.
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486
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Kato Y, Kobayashi K, Watanabe H, Iguchi T. Environmental sex determination in the branchiopod crustacean Daphnia magna: deep conservation of a Doublesex gene in the sex-determining pathway. PLoS Genet 2011; 7:e1001345. [PMID: 21455482 PMCID: PMC3063754 DOI: 10.1371/journal.pgen.1001345] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 02/17/2011] [Indexed: 01/06/2023] Open
Abstract
Sex-determining mechanisms are diverse among animal lineages and can be broadly divided into two major categories: genetic and environmental. In contrast to genetic sex determination (GSD), little is known about the molecular mechanisms underlying environmental sex determination (ESD). The Doublesex (Dsx) genes play an important role in controlling sexual dimorphism in genetic sex-determining organisms such as nematodes, insects, and vertebrates. Here we report the identification of two Dsx genes from Daphnia magna, a freshwater branchiopod crustacean that parthenogenetically produces males in response to environmental cues. One of these genes, designated DapmaDsx1, is responsible for the male trait development when expressed during environmental sex determination. The domain organization of DapmaDsx1 was similar to that of Dsx from insects, which are thought to be the sister group of branchiopod crustaceans. Intriguingly, the molecular basis for sexually dimorphic expression of DapmaDsx1 is different from that of insects. Rather than being regulated sex-specifically at the level of pre–mRNA splicing in the coding region, DapmaDsx1 exhibits sexually dimorphic differences in the abundance of its transcripts. During embryogenesis, expression of DapmaDsx1 was increased only in males and its transcripts were primarily detected in male-specific structures. Knock-down of DapmaDsx1 in male embryos resulted in the production of female traits including ovarian maturation, whereas ectopic expression of DapmaDsx1 in female embryos resulted in the development of male-like phenotypes. Expression patterns of another D. magna Dsx gene, DapmaDsx2, were similar to those of DapmaDsx1, but silencing and overexpression of this gene did not induce any clear phenotypic changes. These results establish DapmaDsx1 as a key regulator of the male phenotype. Our findings reveal how ESD is implemented by selective expression of a fundamental genetic component that is functionally conserved in animals using GSD. We infer that there is an ancient, previously unidentified link between genetic and environmental sex determination. Sex determination is a fundamental biological process that can be broadly divided into two major categories. In genetic sex determination (GSD), sex-specific differentiation results from intrinsic genetic differences between males and females, whereas environmental sex determination (ESD) relies on environmental signals to induce male or female sex determination. In contrast to model organisms that utilize GSD system, environmental sex-determining organisms are poor genetic models. Therefore, although candidate genes involved in ESD have been found in vertebrates, their functions have remained largely unknown, impairing our understanding of ESD and making the comparison of sex-determining genes between both systems difficult. Here, we report the identification of a gene responsible for the production of males during environmental sex determination in the crustacean Daphnia. This gene is homologous to the Doublesex gene that is functionally conserved in animals that use GSD. Expression of Doublesex was increased primarily in male-specific structures. Gain- and loss-of-function analyses established that Daphnia Doublesex gene is a major effector that regulates the male phenotype in Daphnia. We infer that there is an ancient, previously unidentified link between genetic and environmental sex determination.
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Affiliation(s)
- Yasuhiko Kato
- Department of Biotechnology, Graduate School of Engineering, Osaka University, Osaka, Japan
| | - Kaoru Kobayashi
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Aichi, Japan
- Department of Basic Biology, The Graduate School for Advanced Studies, Aichi, Japan
| | - Hajime Watanabe
- Department of Biotechnology, Graduate School of Engineering, Osaka University, Osaka, Japan
| | - Taisen Iguchi
- Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Aichi, Japan
- Department of Basic Biology, The Graduate School for Advanced Studies, Aichi, Japan
- * E-mail:
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487
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Bannister SC, Smith CA, Roeszler KN, Doran TJ, Sinclair AH, Tizard MLV. Manipulation of estrogen synthesis alters MIR202* expression in embryonic chicken gonads. Biol Reprod 2011; 85:22-30. [PMID: 21389341 DOI: 10.1095/biolreprod.110.088476] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Tissue-specific patterns of microRNA (miRNA) expression contribute to organogenesis during embryonic development. Using the embryonic chicken gonads as a model for vertebrate gonadogenesis, we previously reported that miRNAs are expressed in a sexually dimorphic manner during gonadal sex differentiation. Being male biased, we hypothesised that up-regulation of microRNA 202* (MIR202*) is characteristic of testicular differentiation. To address this hypothesis, we used estrogen modulation to induce gonadal sex reversal in embryonic chicken gonads and analyzed changes in MIR202* expression. In ovo injection of estradiol-17beta at Embryonic Day 4.5 (E4.5) caused feminization of male gonads at E9.5 and reduced MIR202* expression to female levels. Female gonads treated at E3.5 with an aromatase inhibitor, which blocks estrogen synthesis, were masculinized by E9.5, and MIR202* expression was increased. Reduced MIR202* expression correlated with reduced expression of the testis-associated genes DMRT1 and SOX9, and up-regulation of ovary-associated genes FOXL2 and CYP19A1 (aromatase). Increased MIR202* expression correlated with down-regulation of FOXL2 and aromatase and up-regulation of DMRT1 and SOX9. These results confirm that up-regulation of MIR202* coincides with testicular differentiation in embryonic chicken gonads.
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Affiliation(s)
- Stephanie C Bannister
- CSIRO Livestock Industries, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
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488
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489
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490
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Herpin A, Schartl M. Dmrt1 genes at the crossroads: a widespread and central class of sexual development factors in fish. FEBS J 2011; 278:1010-9. [PMID: 21281449 DOI: 10.1111/j.1742-4658.2011.08030.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A plethora of corroborative genetic studies led to the view that, across the animal kingdom, the gene-regulatory cascades triggering sexual development bear little resemblance to each other. As a result, the common emerging picture is that the genes at the top of the cascade are not conserved, whereas the downstream genes have homologues in a much broader spectrum of species. Among these downstream effectors, a gene family involved in sex differentiation in organisms as phylogenetically divergent as corals, Caenorhabditis elegans, Drosophila, frogs, fish, birds and mammals is the dmrt gene family. Despite the attention that Dmrt1 factors have received, to date it has not been elucidated how Dmrt1s mediate their activities and putative downstream targets have yet to be characterized. However, a remarkable amount of descriptive expression data has been gathered in a large variety of fish, particularly with respect to early gonadal differentiation and sex change. This minireview aims at distilling the current knowledge of fish dmrt1s, in terms of expression and regulation. It is shown how gonadal identities correlate with dimorphic dmrt1 expression in gonochoristic and hermaphroditic fish species. It is also described how sex steroid hormones affect gonadal identity and dmrt1 expression. Emphasis is also given to recent findings dealing with transcriptional, post-transcriptional, post-translational and functional regulations of the dmrt1a/dmrt1bY gene pair in medaka.
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Affiliation(s)
- Amaury Herpin
- Physiological ChemistryI, University of Wuerzburg, Wuerzburg, Germany.
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491
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Ellegren H. Sex-chromosome evolution: recent progress and the influence of male and female heterogamety. Nat Rev Genet 2011; 12:157-66. [PMID: 21301475 DOI: 10.1038/nrg2948] [Citation(s) in RCA: 156] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It is now clear that sex chromosomes differ from autosomes in many aspects of genome biology, such as organization, gene content and gene expression. Moreover, sex linkage has numerous evolutionary genetic implications. Here, I provide a coherent overview of sex-chromosome evolution and function based on recent data. Heteromorphic sex chromosomes are almost as widespread across the animal and plant kingdoms as sexual reproduction itself and an accumulating body of genetic data reveals interesting similarities, as well as dissimilarities, between organisms with XY or ZW sex-determination systems. Therefore, I discuss how patterns and processes associated with sex linkage in male- and female-heterogametic systems offer a useful contrast in the study of sex-chromosome evolution.
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Affiliation(s)
- Hans Ellegren
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvgen 18D, SE752 36 Uppsala, Sweden.
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492
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Itoh Y, Kampf K, Balakrishnan CN, Arnold AP. Karyotypic polymorphism of the zebra finch Z chromosome. Chromosoma 2011; 120:255-64. [PMID: 21369954 PMCID: PMC3099001 DOI: 10.1007/s00412-010-0308-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 12/02/2010] [Accepted: 12/16/2010] [Indexed: 01/28/2023]
Abstract
We describe a karyotypic polymorphism on the zebra finch Z chromosome. This polymorphism was discovered because of a difference in the position of the centromere and because it occurs at varying frequencies in domesticated colonies in the USA and Germany and among two zebra finch subspecies. Using DNA fluorescent in situ hybridization to map specific Z genes and measurements of DNA replication, we show that this polymorphism is the result of a large pericentric inversion involving the majority of the chromosome. We sequenced a likely breakpoint for the inversion and found many repetitive sequences. Around the breakpoint, there are numerous repetitive sequences and several copies of PAK3 (p21-activated kinase 3)-related sequences (PAK3Z) which showed testes-specific expression by RT-PCR. Our findings further suggest that the sequenced genome of the zebra finch may be derived from a male heterozygote for the Z chromosome polymorphism. This finding, in combination with regional differences in the frequency of the polymorphism, has important consequences for future studies using zebra finches.
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Affiliation(s)
- Yuichiro Itoh
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095-1606, USA.
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493
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Quinn AE, Sarre SD, Ezaz T, Marshall Graves JA, Georges A. Evolutionary transitions between mechanisms of sex determination in vertebrates. Biol Lett 2011; 7:443-8. [PMID: 21212104 DOI: 10.1098/rsbl.2010.1126] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Sex in many organisms is a dichotomous phenotype--individuals are either male or female. The molecular pathways underlying sex determination are governed by the genetic contribution of parents to the zygote, the environment in which the zygote develops or interaction of the two, depending on the species. Systems in which multiple interacting influences or a continuously varying influence (such as temperature) determines a dichotomous outcome have at least one threshold. We show that when sex is viewed as a threshold trait, evolution in that threshold can permit novel transitions between genotypic and temperature-dependent sex determination (TSD) and remarkably, between male (XX/XY) and female (ZZ/ZW) heterogamety. Transitions are possible without substantive genotypic innovation of novel sex-determining mutations or transpositions, so that the master sex gene and sex chromosome pair can be retained in ZW-XY transitions. We also show that evolution in the threshold can explain all observed patterns in vertebrate TSD, when coupled with evolution in embryonic survivorship limits.
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Affiliation(s)
- Alexander E Quinn
- Institute for Applied Ecology, University of Canberra, Canberra 2601, Australia
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494
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Yang X, Zheng J, Qu L, Chen S, Li J, Xu G, Yang N. Methylation Status of cMHM and Expression of Sex-Specific Genes in Adult Sex-Reversed Female Chickens. Sex Dev 2011; 5:147-54. [DOI: 10.1159/000327712] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/01/2011] [Indexed: 11/19/2022] Open
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495
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Abstract
Fanconi anemia (FA) is a human disease of bone marrow failure, leukemia, squamous cell carcinoma, and developmental anomalies, including hypogonadism and infertility. Bone marrow transplants improve hematopoietic phenotypes but do not prevent other cancers. FA arises from mutation in any of the 15 FANC genes that cooperate to repair double stranded DNA breaks by homologous recombination. Zebrafish has a single ortholog of each human FANC gene and unexpectedly, mutations in at least two of them (fancl and fancd1(brca2)) lead to female-to-male sex reversal. Investigations show that, as in human, zebrafish fanc genes are required for genome stability and for suppressing apoptosis in tissue culture cells, in embryos treated with DNA damaging agents, and in meiotic germ cells. The sex reversal phenotype requires the action of Tp53 (p53), an activator of apoptosis. These results suggest that in normal sex determination, zebrafish oocytes passing through meiosis signal the gonadal soma to maintain expression of aromatase, an enzyme that converts androgen to estrogen, thereby feminizing the gonad and the individual. According to this model, normal male and female zebrafish differ in genetic factors that control the strength of the late meiotic oocyte-derived signal, probably by regulating the number of meiotic oocytes, which environmental factors can also alter. Transcripts from fancd1(brca2) localize at the animal pole of the zebrafish oocyte cytoplasm and are required for normal oocyte nuclear architecture, for normal embryonic development, and for preventing ovarian tumors. Embryonic DNA repair and sex reversal phenotypes provide assays for the screening of small molecule libraries for therapeutic substances for FA.
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496
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Genetic Disorders of Sex Differentiation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 707:91-9. [DOI: 10.1007/978-1-4419-8002-1_20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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497
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Al Nadaf S, Waters PD, Koina E, Deakin JE, Jordan KS, Graves JA. Activity map of the tammar X chromosome shows that marsupial X inactivation is incomplete and escape is stochastic. Genome Biol 2010; 11:R122. [PMID: 21182760 PMCID: PMC3046482 DOI: 10.1186/gb-2010-11-12-r122] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 12/08/2010] [Accepted: 12/23/2010] [Indexed: 11/20/2022] Open
Abstract
Background X chromosome inactivation is a spectacular example of epigenetic silencing. In order to deduce how this complex system evolved, we examined X inactivation in a model marsupial, the tammar wallaby (Macropus eugenii). In marsupials, X inactivation is known to be paternal, incomplete and tissue-specific, and occurs in the absence of an XIST orthologue. Results We examined expression of X-borne genes using quantitative PCR, revealing a range of dosage compensation for different loci. To assess the frequency of 1X- or 2X-active fibroblasts, we investigated expression of 32 X-borne genes at the cellular level using RNA-FISH. In female fibroblasts, two-color RNA-FISH showed that genes were coordinately expressed from the same X (active X) in nuclei in which both loci were inactivated. However, loci on the other X escape inactivation independently, with each locus showing a characteristic frequency of 1X-active and 2X-active nuclei, equivalent to stochastic escape. We constructed an activity map of the tammar wallaby inactive X chromosome, which identified no relationship between gene location and extent of inactivation, nor any correlation with the presence or absence of a Y-borne paralog. Conclusions In the tammar wallaby, one X (presumed to be maternal) is expressed in all cells, but genes on the other (paternal) X escape inactivation independently and at characteristic frequencies. The paternal and incomplete X chromosome inactivation in marsupials, with stochastic escape, appears to be quite distinct from the X chromosome inactivation process in eutherians. We find no evidence for a polar spread of inactivation from an X inactivation center.
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Affiliation(s)
- Shafagh Al Nadaf
- Research School of Biology, The Australian National University, Biology Place, Canberra 0200, Australia.
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498
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Bloomfield G, Skelton J, Ivens A, Tanaka Y, Kay RR. Sex determination in the social amoeba Dictyostelium discoideum. Science 2010; 330:1533-6. [PMID: 21148389 DOI: 10.1126/science.1197423] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The genetics of sex determination remain mysterious in many organisms, including some that are otherwise well studied. Here we report the discovery and analysis of the mating-type locus of the model organism Dictyostelium discoideum. Three forms of a single genetic locus specify this species' three mating types: two versions of the locus are entirely different in sequence, and the third resembles a composite of the other two. Single, unrelated genes are sufficient to determine two of the mating types, whereas homologs of both these genes are required in the composite type. The key genes encode polypeptides that possess no recognizable similarity to established protein families. Sex determination in the social amoebae thus appears to use regulators that are unrelated to any others currently known.
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Affiliation(s)
- Gareth Bloomfield
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
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499
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Le Page Y, Diotel N, Vaillant C, Pellegrini E, Anglade I, Mérot Y, Kah O. Aromatase, brain sexualization and plasticity: the fish paradigm. Eur J Neurosci 2010; 32:2105-15. [DOI: 10.1111/j.1460-9568.2010.07519.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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500
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Molecular cloning and characterization of the porcine FTO promoter and coding regions. Mol Biol Rep 2010; 38:2855-62. [PMID: 21104140 DOI: 10.1007/s11033-010-0431-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Accepted: 11/08/2010] [Indexed: 10/18/2022]
Abstract
The fat mass and obesity associated gene (FTO) has been widely reported to be associated with fat mass or fat deposition in different species. In the present study, we cloned both promoter and coding regions of the gene in pigs with over 5 Kb of sequence for the former region and 1,596 bp for the latter region. Comparative analysis of the promoter region among 20 species including pig revealed four conserved regions that harbor transcriptional factors involved in adipose differentiation. Using a pooled DNA sequencing approach, we discovered 39 single nucleotide polymorphisms (SNPs) in the pig FTO gene and four of them were genotyped on 716 pigs representing 3 European and 18 Chinese indigenous pig breeds plus samples of wild boars. We found that TCGG is a favored haplotype in Chinese wild boars and 16 indigenous pig breeds, while Li Cha Black and Tong Cheng pigs had the specific dominant haplotypes of TTGG and TCGA, respectively. ATGA was the main haplotype found in Large White and Duroc pigs, but the haplotype of ATGG was the major type in Landrace. Taken together, these data provide a valuable foundation for the community to fully study the function of FTO gene in pigs.
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