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Ye Z, Bishop T, Wang Y, Shahriari R, Lynch M. Evolution of sex determination in crustaceans. MARINE LIFE SCIENCE & TECHNOLOGY 2023; 5:1-11. [PMID: 37073332 PMCID: PMC10077267 DOI: 10.1007/s42995-023-00163-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 12/28/2022] [Indexed: 05/03/2023]
Abstract
Sex determination (SD) involves mechanisms that determine whether an individual will develop into a male, female, or in rare cases, hermaphrodite. Crustaceans harbor extremely diverse SD systems, including hermaphroditism, environmental sex determination (ESD), genetic sex determination (GSD), and cytoplasmic sex determination (e.g., Wolbachia controlled SD systems). Such diversity lays the groundwork for researching the evolution of SD in crustaceans, i.e., transitions among different SD systems. However, most previous research has focused on understanding the mechanism of SD within a single lineage or species, overlooking the transition across different SD systems. To help bridge this gap, we summarize the understanding of SD in various clades of crustaceans, and discuss how different SD systems might evolve from one another. Furthermore, we review the genetic basis for transitions between different SD systems (i.e., Dmrt genes) and propose the microcrustacean Daphnia (clade Branchiopoda) as a model to study the transition from ESD to GSD.
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Affiliation(s)
- Zhiqiang Ye
- Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287 USA
| | - Trent Bishop
- Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287 USA
| | - Yaohai Wang
- Institute of Evolution and Marine Biodiversity, KLMME, Ocean University of China, Qingdao, 266003 China
| | - Ryan Shahriari
- Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287 USA
| | - Michael Lynch
- Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287 USA
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Song H, Park HJ, Lee WY, Lee KH. Models and Molecular Markers of Spermatogonial Stem Cells in Vertebrates: To Find Models in Nonmammals. Stem Cells Int 2022; 2022:4755514. [PMID: 35685306 PMCID: PMC9174007 DOI: 10.1155/2022/4755514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 03/21/2022] [Accepted: 04/17/2022] [Indexed: 11/24/2022] Open
Abstract
Spermatogonial stem cells (SSCs) are the germline stem cells that are essential for the maintenance of spermatogenesis in the testis. However, it has not been sufficiently understood in amphibians, reptiles, and fish because numerous studies have been focused mainly on mammals. The aim of this review is to discuss scientific ways to elucidate SSC models of nonmammals in the context of the evolution of testicular organization since rodent SSC models. To further understand the SSC models in nonmammals, we point out common markers of an SSC pool (undifferentiated spermatogonia) in various types of testes where the kinetics of the SSC pool appears. This review includes the knowledge of (1) common molecular markers of vertebrate type A spermatogonia including putative SSC markers, (2) localization of the markers on the spermatogonia that have been reported in previous studies, (3) highlighting the most common markers in vertebrates, and (4) suggesting ways of finding SSC models in nonmammals.
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Affiliation(s)
- Hyuk Song
- Department of Stem Cell and Regenerative Technology, KIT, Konkuk University, Seoul 05029, Republic of Korea
| | - Hyun-Jung Park
- Department of Animal Biotechnology, College of Life Science and Natural Resources, Sangji University, Wonju-si 26339, Republic of Korea
| | - Won-Young Lee
- Department of Animal Science, Korea National College of Agriculture and Fisheries, Jeonju-si 54874, Republic of Korea
| | - Kyung Hoon Lee
- Department of Stem Cell and Regenerative Technology, KIT, Konkuk University, Seoul 05029, Republic of Korea
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Mezzasalma M, Guarino FM, Odierna G. Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from a Systematic Distribution of Available Data? Genes (Basel) 2021; 12:1341. [PMID: 34573323 PMCID: PMC8468487 DOI: 10.3390/genes12091341] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/20/2021] [Accepted: 08/27/2021] [Indexed: 01/19/2023] Open
Abstract
Lizards represent unique model organisms in the study of sex determination and sex chromosome evolution. Among tetrapods, they are characterized by an unparalleled diversity of sex determination systems, including temperature-dependent sex determination (TSD) and genetic sex determination (GSD) under either male or female heterogamety. Sex chromosome systems are also extremely variable in lizards. They include simple (XY and ZW) and multiple (X1X2Y and Z1Z2W) sex chromosome systems and encompass all the different hypothesized stages of diversification of heterogametic chromosomes, from homomorphic to heteromorphic and completely heterochromatic sex chromosomes. The co-occurrence of TSD, GSD and different sex chromosome systems also characterizes different lizard taxa, which represent ideal models to study the emergence and the evolutionary drivers of sex reversal and sex chromosome turnover. In this review, we present a synthesis of general genome and karyotype features of non-snakes squamates and discuss the main theories and evidences on the evolution and diversification of their different sex determination and sex chromosome systems. We here provide a systematic assessment of the available data on lizard sex chromosome systems and an overview of the main cytogenetic and molecular methods used for their identification, using a qualitative and quantitative approach.
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Affiliation(s)
- Marcello Mezzasalma
- Department of Biology, University of Naples Federico II, I-80126 Naples, Italy; (F.M.G.); (G.O.)
- CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO, Universidade do Porto, Rua Padre Armando Quintas 7, 4485-661 Vairaõ, Portugal
| | - Fabio M. Guarino
- Department of Biology, University of Naples Federico II, I-80126 Naples, Italy; (F.M.G.); (G.O.)
| | - Gaetano Odierna
- Department of Biology, University of Naples Federico II, I-80126 Naples, Italy; (F.M.G.); (G.O.)
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Alam SMI, Sarre SD, Georges A, Ezaz T. Karyotype Characterisation of Two Australian Dragon Lizards (Squamata: Agamidae: Amphibolurinae) Reveals Subtle Chromosomal Rearrangements Between Related Species with Similar Karyotypes. Cytogenet Genome Res 2020; 160:610-624. [PMID: 33207346 DOI: 10.1159/000511344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 09/02/2020] [Indexed: 11/19/2022] Open
Abstract
Agamid lizards (Squamata: Agamidae) are karyotypically heterogeneous. Among the 101 species currently described from Australia, all are from the subfamily Amphibolurinae. This group is, with some exceptions, karyotypically conserved, and all species involving heterogametic sex show female heterogamety. Here, we describe the chromosomes of 2 additional Australian agamid lizards, Tympanocryptis lineata and Rankinia diemensis. These species are phylogenetically and cytogenetically sisters to the well-characterised Pogona vitticeps, but their sex chromosomes and other chromosomal characteristics are unknown. In this study, we applied advanced molecular cytogenetic techniques, such as fluorescence in situ hybridisation (FISH) and cross-species gene mapping, to characterise chromosomes and to identify sex chromosomes in these species. Our data suggest that both species have a conserved karyotype with P. vitticeps but with subtle rearrangements in the chromosomal landscapes. We could identify that T. lineata possesses a female heterogametic system (ZZ/ZW) with a pair of sex microchromosomes, while R. diemensis may have heterogametic sex chromosomes, but this requires further investigations. Our study shows the pattern of chromosomal rearrangements between closely related species, explaining the speciation within Australian agamid lizards of similar karyotypes.
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Affiliation(s)
- Shayer M I Alam
- Centre for Conservation Ecology and Genetics, Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia,
| | - Stephen D Sarre
- Centre for Conservation Ecology and Genetics, Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Arthur Georges
- Centre for Conservation Ecology and Genetics, Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Tariq Ezaz
- Centre for Conservation Ecology and Genetics, Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia
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Dissanayake DSB, Holleley CE, Hill LK, O'Meally D, Deakin JE, Georges A. Identification of Y chromosome markers in the eastern three-lined skink (Bassiana duperreyi) using in silico whole genome subtraction. BMC Genomics 2020; 21:667. [PMID: 32993477 PMCID: PMC7526180 DOI: 10.1186/s12864-020-07071-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 09/14/2020] [Indexed: 12/15/2022] Open
Abstract
Background Homologous sex chromosomes can differentiate over time because recombination is suppressed in the region of the sex determining locus, leading to the accumulation of repeats, progressive loss of genes that lack differential influence on the sexes and sequence divergence on the hemizygous homolog. Divergence in the non-recombining regions leads to the accumulation of Y or W specific sequence useful for developing sex-linked markers. Here we use in silico whole-genome subtraction to identify putative sex-linked sequences in the scincid lizard Bassiana duperreyi which has heteromorphic XY sex chromosomes. Results We generated 96.7 × 109 150 bp paired-end genomic sequence reads from a XY male and 81.4 × 109 paired-end reads from an XX female for in silico whole genome subtraction to yield Y enriched contigs. We identified 7 reliable markers which were validated as Y chromosome specific by polymerase chain reaction (PCR) against a panel of 20 males and 20 females. Conclusions The sex of B. duperreyi can be reversed by low temperatures (XX genotype reversed to a male phenotype). We have developed sex-specific markers to identify the underlying genotypic sex and its concordance or discordance with phenotypic sex in wild populations of B. duperreyi. Our pipeline can be applied to isolate Y or W chromosome-specific sequences of any organism and is not restricted to sequence residing within single-copy genes. This study greatly improves our knowledge of the Y chromosome in B. duperreyi and will enhance future studies of reptile sex determination and sex chromosome evolution.
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Affiliation(s)
- Duminda Sampath Bandara Dissanayake
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia.,Australian National Wildlife Collection, CSIRO, Canberra, ACT, 2911, Australia
| | - Clare Ellen Holleley
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia.,Australian National Wildlife Collection, CSIRO, Canberra, ACT, 2911, Australia
| | - Laura Kate Hill
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia
| | - Denis O'Meally
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia.,Present Address: Centre for Gene Therapy, Beckman Research Institute of the City of Hope, Duarte, CA, USA
| | - Janine Eileen Deakin
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia.
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Viana PF, Ezaz T, de Bello Cioffi M, Liehr T, Al-Rikabi A, Goll LG, Rocha AM, Feldberg E. Landscape of snake' sex chromosomes evolution spanning 85 MYR reveals ancestry of sequences despite distinct evolutionary trajectories. Sci Rep 2020; 10:12499. [PMID: 32719365 PMCID: PMC7385105 DOI: 10.1038/s41598-020-69349-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 07/06/2020] [Indexed: 11/09/2022] Open
Abstract
Most of snakes exhibit a ZZ/ZW sex chromosome system, with different stages of degeneration. However, undifferentiated sex chromosomes and unique Y sex-linked markers, suggest that an XY system has also evolved in ancestral lineages. Comparative cytogenetic mappings revealed that several genes share ancestry among X, Y and Z chromosomes, implying that XY and ZW may have undergone transitions during serpent's evolution. In this study, we performed a comparative cytogenetic analysis to identify homologies of sex chromosomes across ancestral (Henophidia) and more recent (Caenophidia) snakes. Our analysis suggests that, despite ~ 85 myr of independent evolution, henophidians and caenophidians retained conserved synteny over much of their genomes. However, our findings allowed us to discover that ancestral and recent lineages of snakes do not share the same sex chromosome and followed distinct pathways for sex chromosomes evolution.
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Affiliation(s)
- Patrik F Viana
- Coordenação de Biodiversidade, Laboratory of Animal Genetics, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, Petrópolis, Manaus, AM, 69067-375, Brazil.
| | - Tariq Ezaz
- Institute for Applied Ecology, Faculty of Science and Technology, University of Canberra, ACT 12, Canberra, 2616, Australia
| | - Marcelo de Bello Cioffi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil.,Institute of Human Genetics, University Hospital Jena, Am Klinikum 1, 07747, Jena, Germany
| | - Thomas Liehr
- Institute of Human Genetics, University Hospital Jena, Am Klinikum 1, 07747, Jena, Germany
| | - Ahmed Al-Rikabi
- Institute of Human Genetics, University Hospital Jena, Am Klinikum 1, 07747, Jena, Germany
| | - Leonardo G Goll
- Coordenação de Biodiversidade, Laboratory of Animal Genetics, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, Petrópolis, Manaus, AM, 69067-375, Brazil
| | - Anderson M Rocha
- Faculdade Cathedral, Laboratório de Zoologia Aplicada de Vertebrados Terrestres E Aquáticos, Av. Luis Canuto Chaves 293, Boa Vista, RR, Brazil
| | - Eliana Feldberg
- Coordenação de Biodiversidade, Laboratory of Animal Genetics, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, Petrópolis, Manaus, AM, 69067-375, Brazil
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Cross-Species BAC Mapping Highlights Conservation of Chromosome Synteny across Dragon Lizards (Squamata: Agamidae). Genes (Basel) 2020; 11:genes11060698. [PMID: 32630412 PMCID: PMC7348930 DOI: 10.3390/genes11060698] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 01/23/2023] Open
Abstract
Dragon lizards (Squamata: Agamidae) comprise about 520 species in six subfamilies distributed across Asia, Australasia and Africa. Only five species are known to have sex chromosomes. All of them possess ZZ/ZW sex chromosomes, which are microchromosomes in four species from the subfamily Amphibolurinae, but much larger in Phrynocephalus vlangalii from the subfamily Agaminae. In most previous studies of these sex chromosomes, the focus has been on Australian species from the subfamily Amphibolurinae, but only the sex chromosomes of the Australian central bearded dragon (Pogona vitticeps) are well-characterized cytogenetically. To determine the level of synteny of the sex chromosomes of P. vitticeps across agamid subfamilies, we performed cross-species two-colour FISH using two bacterial artificial chromosome (BAC) clones from the pseudo-autosomal regions of P. vitticeps. We mapped these two BACs across representative species from all six subfamilies as well as two species of chameleons, the sister group to agamids. We found that one of these BAC sequences is conserved in macrochromosomes and the other in microchromosomes across the agamid lineages. However, within the Amphibolurinae, there is evidence of multiple chromosomal rearrangements with one of the BACs mapping to the second-largest chromosome pair and to the microchromosomes in multiple species including the sex chromosomes of P. vitticeps. Intriguingly, no hybridization signal was observed in chameleons for either of these BACs, suggesting a likely agamid origin of these sequences. Our study shows lineage-specific evolution of sequences/syntenic blocks and successive rearrangements and reveals a complex history of sequences leading to their association with important biological processes such as the evolution of sex chromosomes and sex determination.
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8
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Do sex chromosomes of snakes, monitor lizards, and iguanian lizards result from multiple fission of an “ancestral amniote super-sex chromosome”? Chromosome Res 2020; 28:209-228. [DOI: 10.1007/s10577-020-09631-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/22/2020] [Accepted: 03/24/2020] [Indexed: 01/12/2023]
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9
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ZW Sex Chromosomes in Australian Dragon Lizards (Agamidae) Originated from a Combination of Duplication and Translocation in the Nucleolar Organising Region. Genes (Basel) 2019; 10:genes10110861. [PMID: 31671601 PMCID: PMC6895791 DOI: 10.3390/genes10110861] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 10/22/2019] [Accepted: 10/29/2019] [Indexed: 12/14/2022] Open
Abstract
Sex chromosomes in some reptiles share synteny with distantly related amniotes in regions orthologous to squamate chromosome 2. The latter finding suggests that chromosome 2 was formerly part of a larger ancestral (amniote) super-sex chromosome and raises questions about how sex chromosomes are formed and modified in reptiles. Australian dragon lizards (Agamidae) are emerging as an excellent model for studying these processes. In particular, they exhibit both genotypic (GSD) and temperature-dependent (TSD) sex determination, show evidence of transitions between the two modes and have evolved non-homologous ZW sex microchromosomes even within the same evolutionary lineage. They therefore represent an excellent group to probe further the idea of a shared ancestral super-sex chromosome and to investigate mechanisms for transition between different sex chromosome forms. Here, we compare sex chromosome homology among eight dragon lizard species from five genera to identify key cytological differences and the mechanisms that may be driving sex chromosome evolution in this group. We performed fluorescence in situ hybridisation to physically map bacterial artificial chromosome (BAC) clones from the bearded dragon, Pogona vitticeps’ ZW sex chromosomes and a nucleolar organising region (NOR) probe in males and females of eight Agamid species exhibiting either GSD or TSD. We show that the sex chromosome derived BAC clone hybridises near the telomere of chromosome 2q in all eight species examined. This clone also hybridises to the sex microchromosomes of three species (P vitticeps, P. barbata and Diporiphora nobbi) and a pair of microchromosomes in three others (Ctenophorus pictus, Amphibolurus norrisi and Amphibolurus muricatus). No other chromosomes are marked by the probe in two species from the closely related genus Physignathus. A probe bearing nucleolar organising region (NOR) sequences maps close to the telomere of chromosome 2q in all eight species, and to the ZW pair in P. vitticeps and P. barbata, the W microchromosome in D. nobbi, and several microchromosomes in P. cocincinus. Our findings provide evidence of sequence homology between chromosome 2 and the sex chromosomes of multiple agamids. These data support the hypothesis that there was an ancestral sex chromosome in amniotes that gave rise to squamate chromosome 2 and raises the prospect that some particular property of this chromosome has favoured its role as a sex chromosome in amniotes. It is likely that the amplification of repetitive sequences associated with this region has driven the high level of heterochromatinisation of the sex-specific chromosomes in three species of agamid. Our data suggest a possible mechanism for chromosome rearrangement, including inversion and duplication near the telomeric regions of the ancestral chromosome 2 and subsequent translocation to the ZW sex microchromosomes in three agamid species. It is plausible that these chromosome rearrangements involving sex chromosomes also drove speciation in this group.
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Hill PL, Burridge CP, Ezaz T, Wapstra E. Conservation of Sex-Linked Markers among Conspecific Populations of a Viviparous Skink, Niveoscincus ocellatus, Exhibiting Genetic and Temperature-Dependent Sex Determination. Genome Biol Evol 2018; 10:1079-1087. [PMID: 29659810 PMCID: PMC5905450 DOI: 10.1093/gbe/evy042] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/01/2018] [Indexed: 12/18/2022] Open
Abstract
Sex determination systems are exceptionally diverse and have undergone multiple and independent evolutionary transitions among species, particularly reptiles. However, the mechanisms underlying these transitions have not been established. Here, we tested for differences in sex-linked markers in the only known reptile that is polymorphic for sex determination system, the spotted snow skink, Niveoscincus ocellatus, to quantify the genomic differences that have accompanied this transition. In a highland population, sex is determined genetically, whereas in a lowland population, offspring sex ratio is influenced by temperature. We found a similar number of sex-linked loci in each population, including shared loci, with genotypes consistent with male heterogamety (XY). However, population-specific linkage disequilibrium suggests greater differentiation of sex chromosomes in the highland population. Our results suggest that transitions between sex determination systems can be facilitated by subtle genetic differences.
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Affiliation(s)
- Peta L Hill
- School of Biological Sciences, University of Tasmania, Sandy Bay, Tasmania, Australia
| | | | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Erik Wapstra
- School of Biological Sciences, University of Tasmania, Sandy Bay, Tasmania, Australia
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11
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Abstract
Making my career in Australia exposed me to the tyranny of distance, but it gave me opportunities to study our unique native fauna. Distantly related animal species present genetic variation that we can use to explore the most fundamental biological structures and processes. I have compared chromosomes and genomes of kangaroos and platypus, tiger snakes and emus, devils (Tasmanian) and dragons (lizards). I particularly love the challenges posed by sex chromosomes, which, apart from determining sex, provide stunning examples of epigenetic control and break all the evolutionary rules that we currently understand. Here I describe some of those amazing animals and the insights on genome structure, function, and evolution they have afforded us. I also describe my sometimes-random walk in science and the factors and people who influenced my direction. Being a woman in science is still not easy, and I hope others will find encouragement and empathy in my story.
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Affiliation(s)
- Jennifer A. Marshall Graves
- School of Life Science, La Trobe University, Melbourne, Victoria 3086, Australia
- Australia Institute of Applied Ecology, University of Canberra, ACT 2617, Australia
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12
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Melville J, Hunjan S, McLean F, Mantziou G, Boysen K, Parry LJ. Expression of a hindlimb-determining factor Pitx1 in the forelimb of the lizard Pogona vitticeps during morphogenesis. Open Biol 2017; 6:rsob.160252. [PMID: 27784790 PMCID: PMC5090065 DOI: 10.1098/rsob.160252] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 09/29/2016] [Indexed: 11/24/2022] Open
Abstract
With over 9000 species, squamates, which include lizards and snakes, are the largest group of reptiles and second-largest order of vertebrates, spanning a vast array of appendicular skeletal morphology. As such, they provide a promising system for examining developmental and molecular processes underlying limb morphology. Using the central bearded dragon (Pogona vitticeps) as the primary study model, we examined limb morphometry throughout embryonic development and characterized the expression of three known developmental genes (GHR, Pitx1 and Shh) from early embryonic stage through to hatchling stage via reverse transcription quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC). In this study, all genes were found to be transcribed in both the forelimbs and hindlimbs of P. vitticeps. While the highest level of GHR expression occurred at the hatchling stage, Pitx1 and Shh expression was greatest earlier during embryogenesis, which coincides with the onset of the differentiation between forelimb and hindlimb length. We compared our finding of Pitx1 expression—a hindlimb-determining gene—in the forelimbs of P. vitticeps to that in a closely related Australian agamid lizard, Ctenophorus pictus, where we found Pitx1 expression to be more highly expressed in the hindlimb compared with the forelimb during early and late morphogenesis—a result consistent with that found across other tetrapods. Expression of Pitx1 in forelimbs has only rarely been documented, including via in situ hybridization in a chicken and a frog. Our findings from both RT-qPCR and IHC indicate that further research across a wider range of tetrapods is needed to more fully understand evolutionary variation in molecular processes underlying limb morphology.
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Affiliation(s)
| | | | | | | | - Katja Boysen
- Museum Victoria, Carlton, Victoria 3001, Australia
| | - Laura J Parry
- School of Biosciences, University of Melbourne, Parkville, Victoria 3010, Australia
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13
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Whiteley SL, Holleley CE, Ruscoe WA, Castelli M, Whitehead DL, Lei J, Georges A, Weisbecker V. Sex determination mode does not affect body or genital development of the central bearded dragon ( Pogona vitticeps). EvoDevo 2017; 8:25. [PMID: 29225770 PMCID: PMC5716226 DOI: 10.1186/s13227-017-0087-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 11/21/2017] [Indexed: 11/10/2022] Open
Abstract
Background The development of male- or female-specific phenotypes in squamates is typically controlled by either temperature-dependent sex determination (TSD) or chromosome-based genetic sex determination (GSD). However, while sex determination is a major switch in individual phenotypic development, it is unknownhow evolutionary transitions between GSD and TSD might impact on the evolution of squamate phenotypes, particularly the fast-evolving and diverse genitalia. Here, we take the unique opportunity of studying the impact of both sex determination mechanisms on the embryological development of the central bearded dragon (Pogona vitticeps). This is possible because of the transitional sex determination system of this species, in which genetically male individuals reverse sex at high incubation temperatures. This can trigger the evolutionary transition of GSD to TSD in a single generation, making P. vitticeps an ideal model organism for comparing the effects of both sex determination processes in the same species. Results We conducted four incubation experiments on 265 P. vitticeps eggs, covering two temperature regimes ("normal" at 28 °C and "sex reversing" at 36 °C) and the two maternal sexual genotypes (concordant ZW females or sex-reversed ZZ females). From this, we provide the first detailed staging system for the species, with a focus on genital and limb development. This was augmented by a new sex chromosome identification methodology for P. vitticeps that is non-destructive to the embryo. We found a strong correlation between embryo age and embryo stage. Aside from faster growth in 36 °C treatments, body and external genital development was entirely unperturbed by temperature, sex reversal or maternal sexual genotype. Unexpectedly, all females developed hemipenes (the genital phenotype of adult male P. vitticeps), which regress close to hatching. Conclusions The tight correlation between embryo age and embryo stage allows the precise targeting of specific developmental periods in the emerging field of molecular research on P. vitticeps. The stability of genital development in all treatments suggests that the two sex-determining mechanisms have little impact on genital evolution, despite their known role in triggering genital development. Hemipenis retention in developing female P. vitticeps, together with frequent occurrences of hemipenis-like structures during development in other squamate species, raises the possibility of a bias towards hemipenis formation in the ancestral developmental programme for squamate genitalia.
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Affiliation(s)
- Sarah L Whiteley
- School of Biological Sciences, University of Queensland, Brisbane, QLD Australia.,Australian National Wildlife Collection, National Research Collections Australia, CSIRO, Canberra, ACT Australia.,Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Clare E Holleley
- Australian National Wildlife Collection, National Research Collections Australia, CSIRO, Canberra, ACT Australia.,Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Wendy A Ruscoe
- Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Meghan Castelli
- Australian National Wildlife Collection, National Research Collections Australia, CSIRO, Canberra, ACT Australia.,Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Darryl L Whitehead
- School of Biomedical Science, University of Queensland, Brisbane, QLD Australia
| | - Juan Lei
- School of Biological Sciences, University of Queensland, Brisbane, QLD Australia
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Vera Weisbecker
- School of Biological Sciences, University of Queensland, Brisbane, QLD Australia
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14
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Marin R, Cortez D, Lamanna F, Pradeepa MM, Leushkin E, Julien P, Liechti A, Halbert J, Brüning T, Mössinger K, Trefzer T, Conrad C, Kerver HN, Wade J, Tschopp P, Kaessmann H. Convergent origination of a Drosophila-like dosage compensation mechanism in a reptile lineage. Genome Res 2017; 27:1974-1987. [PMID: 29133310 PMCID: PMC5741051 DOI: 10.1101/gr.223727.117] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 10/23/2017] [Indexed: 01/01/2023]
Abstract
Sex chromosomes differentiated from different ancestral autosomes in various vertebrate lineages. Here, we trace the functional evolution of the XY Chromosomes of the green anole lizard (Anolis carolinensis), on the basis of extensive high-throughput genome, transcriptome and histone modification sequencing data and revisit dosage compensation evolution in representative mammals and birds with substantial new expression data. Our analyses show that Anolis sex chromosomes represent an ancient XY system that originated at least ≈160 million years ago in the ancestor of Iguania lizards, shortly after the separation from the snake lineage. The age of this system approximately coincides with the ages of the avian and two mammalian sex chromosomes systems. To compensate for the almost complete Y Chromosome degeneration, X-linked genes have become twofold up-regulated, restoring ancestral expression levels. The highly efficient dosage compensation mechanism of Anolis represents the only vertebrate case identified so far to fully support Ohno's original dosage compensation hypothesis. Further analyses reveal that X up-regulation occurs only in males and is mediated by a male-specific chromatin machinery that leads to global hyperacetylation of histone H4 at lysine 16 specifically on the X Chromosome. The green anole dosage compensation mechanism is highly reminiscent of that of the fruit fly, Drosophila melanogaster. Altogether, our work unveils the convergent emergence of a Drosophila-like dosage compensation mechanism in an ancient reptilian sex chromosome system and highlights that the evolutionary pressures imposed by sex chromosome dosage reductions in different amniotes were resolved in fundamentally different ways.
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Affiliation(s)
- Ray Marin
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland.,Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Diego Cortez
- Center for Genomic Sciences, UNAM, CP62210 Cuernavaca, Mexico
| | - Francesco Lamanna
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany
| | - Madapura M Pradeepa
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, United Kingdom
| | - Evgeny Leushkin
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany
| | - Philippe Julien
- EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation, 08003 Barcelona, Spain
| | - Angélica Liechti
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Jean Halbert
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Thoomke Brüning
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany
| | - Katharina Mössinger
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany
| | - Timo Trefzer
- Department of Theoretical Bioinformatics, German Cancer Research Center/BioQuant, D-69120 Heidelberg, Germany
| | - Christian Conrad
- Department of Theoretical Bioinformatics, German Cancer Research Center/BioQuant, D-69120 Heidelberg, Germany
| | - Halie N Kerver
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA
| | - Juli Wade
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA.,Department of Psychology, Michigan State University, East Lansing, Michigan 48824, USA
| | - Patrick Tschopp
- Institute of Zoology, University of Basel, 4051 Basel, Switzerland
| | - Henrik Kaessmann
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany
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15
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Yano CF, Bertollo LAC, Ezaz T, Trifonov V, Sember A, Liehr T, Cioffi MB. Highly conserved Z and molecularly diverged W chromosomes in the fish genus Triportheus (Characiformes, Triportheidae). Heredity (Edinb) 2016; 118:276-283. [PMID: 28000659 DOI: 10.1038/hdy.2016.83] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 06/24/2016] [Accepted: 07/08/2016] [Indexed: 11/09/2022] Open
Abstract
The main objectives of this study were to test: (1) whether the W-chromosome differentiation matches to species' evolutionary divergence (phylogenetic concordance) and (2) whether sex chromosomes share a common ancestor within a congeneric group. The monophyletic genus Triportheus (Characiformes, Triportheidae) was the model group for this study. All species in this genus so far analyzed have ZW sex chromosome system, where the Z is always the largest chromosome of the karyotype, whereas the W chromosome is highly variable ranging from almost homomorphic to highly heteromorphic. We applied conventional and molecular cytogenetic approaches including C-banding, ribosomal DNA mapping, comparative genomic hybridization (CGH) and cross-species whole chromosome painting (WCP) to test our questions. We developed Z- and W-chromosome paints from T. auritus for cross-species WCP and performed CGH in a representative species (T. signatus) to decipher level of homologies and rates of differentiation of W chromosomes. Our study revealed that the ZW sex chromosome system had a common origin, showing highly conserved Z chromosomes and remarkably divergent W chromosomes. Notably, the W chromosomes have evolved to different shapes and sequence contents within ~15-25 Myr of divergence time. Such differentiation highlights a dynamic process of W-chromosome evolution within congeneric species of Triportheus.
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Affiliation(s)
- C F Yano
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - L A C Bertollo
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - T Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory, Australia
| | - V Trifonov
- Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russia
| | - A Sember
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Liběchov, Czech Republic
| | - T Liehr
- Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Jena, Germany
| | - M B Cioffi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
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16
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Holleley CE, Sarre SD, O'Meally D, Georges A. Sex Reversal in Reptiles: Reproductive Oddity or Powerful Driver of Evolutionary Change? Sex Dev 2016; 10:279-287. [DOI: 10.1159/000450972] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2016] [Indexed: 12/16/2022] Open
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17
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Ezaz T, Srikulnath K, Graves JAM. Origin of Amniote Sex Chromosomes: An Ancestral Super-Sex Chromosome, or Common Requirements? J Hered 2016; 108:94-105. [DOI: 10.1093/jhered/esw053] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 08/22/2016] [Indexed: 12/28/2022] Open
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18
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Montiel EE, Badenhorst D, Lee LS, Literman R, Trifonov V, Valenzuela N. Cytogenetic Insights into the Evolution of Chromosomes and Sex Determination Reveal Striking Homology of Turtle Sex Chromosomes to Amphibian Autosomes. Cytogenet Genome Res 2016; 148:292-304. [DOI: 10.1159/000447478] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2016] [Indexed: 11/19/2022] Open
Abstract
Turtle karyotypes are highly conserved compared to other vertebrates; yet, variation in diploid number (2n = 26-68) reflects profound genomic reorganization, which correlates with evolutionary turnovers in sex determination. We evaluate the published literature and newly collected comparative cytogenetic data (G- and C-banding, 18S-NOR, and telomere-FISH mapping) from 13 species spanning 2n = 28-68 to revisit turtle genome evolution and sex determination. Interstitial telomeric sites were detected in multiple lineages that underwent diploid number and sex determination turnovers, suggesting chromosomal rearrangements. C-banding revealed potential interspecific variation in centromere composition and interstitial heterochromatin at secondary constrictions. 18S-NORs were detected in secondary constrictions in a single chromosomal pair per species, refuting previous reports of multiple NORs in turtles. 18S-NORs are linked to ZW chromosomes in Apalone and Pelodiscus and to X (not Y) in Staurotypus. Notably, comparative genomics across amniotes revealed that the sex chromosomes of several turtles, as well as mammals and some lizards, are homologous to components of Xenopus tropicalis XTR1 (carrying Dmrt1). Other turtle sex chromosomes are homologous to XTR4 (carrying Wt1). Interestingly, all known turtle sex chromosomes, except in Trionychidae, evolved via inversions around Dmrt1 or Wt1. Thus, XTR1 appears to represent an amniote proto-sex chromosome (perhaps linked ancestrally to XTR4) that gave rise to turtle and other amniote sex chromosomes.
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19
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Deakin JE, Edwards MJ, Patel H, O'Meally D, Lian J, Stenhouse R, Ryan S, Livernois AM, Azad B, Holleley CE, Li Q, Georges A. Anchoring genome sequence to chromosomes of the central bearded dragon (Pogona vitticeps) enables reconstruction of ancestral squamate macrochromosomes and identifies sequence content of the Z chromosome. BMC Genomics 2016; 17:447. [PMID: 27286959 PMCID: PMC4902969 DOI: 10.1186/s12864-016-2774-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 05/25/2016] [Indexed: 12/30/2022] Open
Abstract
Background Squamates (lizards and snakes) are a speciose lineage of reptiles displaying considerable karyotypic diversity, particularly among lizards. Understanding the evolution of this diversity requires comparison of genome organisation between species. Although the genomes of several squamate species have now been sequenced, only the green anole lizard has any sequence anchored to chromosomes. There is only limited gene mapping data available for five other squamates. This makes it difficult to reconstruct the events that have led to extant squamate karyotypic diversity. The purpose of this study was to anchor the recently sequenced central bearded dragon (Pogona vitticeps) genome to chromosomes to trace the evolution of squamate chromosomes. Assigning sequence to sex chromosomes was of particular interest for identifying candidate sex determining genes. Results By using two different approaches to map conserved blocks of genes, we were able to anchor approximately 42 % of the dragon genome sequence to chromosomes. We constructed detailed comparative maps between dragon, anole and chicken genomes, and where possible, made broader comparisons across Squamata using cytogenetic mapping information for five other species. We show that squamate macrochromosomes are relatively well conserved between species, supporting findings from previous molecular cytogenetic studies. Macrochromosome diversity between members of the Toxicofera clade has been generated by intrachromosomal, and a small number of interchromosomal, rearrangements. We reconstructed the ancestral squamate macrochromosomes by drawing upon comparative cytogenetic mapping data from seven squamate species and propose the events leading to the arrangements observed in representative species. In addition, we assigned over 8 Mbp of sequence containing 219 genes to the Z chromosome, providing a list of genes to begin testing as candidate sex determining genes. Conclusions Anchoring of the dragon genome has provided substantial insight into the evolution of squamate genomes, enabling us to reconstruct ancestral macrochromosome arrangements at key positions in the squamate phylogeny, demonstrating that fusions between macrochromosomes or fusions of macrochromosomes and microchromosomes, have played an important role during the evolution of squamate genomes. Assigning sequence to the sex chromosomes has identified NR5A1 as a promising candidate sex determining gene in the dragon. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2774-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Janine E Deakin
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia.
| | - Melanie J Edwards
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
| | - Hardip Patel
- John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
| | - Denis O'Meally
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
| | - Jinmin Lian
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083, China
| | - Rachael Stenhouse
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
| | - Sam Ryan
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
| | - Alexandra M Livernois
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
| | - Bhumika Azad
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia.,John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
| | - Clare E Holleley
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
| | - Qiye Li
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083, China.,Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, Copenhagen, 1350, Denmark
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601, Australia
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20
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Giovannotti M, Trifonov VA, Paoletti A, Kichigin IG, O’Brien PCM, Kasai F, Giovagnoli G, Ng BL, Ruggeri P, Cerioni PN, Splendiani A, Pereira JC, Olmo E, Rens W, Caputo Barucchi V, Ferguson-Smith MA. New insights into sex chromosome evolution in anole lizards (Reptilia, Dactyloidae). Chromosoma 2016; 126:245-260. [DOI: 10.1007/s00412-016-0585-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 02/16/2016] [Accepted: 03/10/2016] [Indexed: 10/22/2022]
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21
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Graves JAM. How Australian mammals contributed to our understanding of sex determination and sex chromosomes. AUST J ZOOL 2016. [DOI: 10.1071/zo16054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Marsupials and monotremes can be thought of as independent experiments in mammalian evolution. The discovery of the human male-determining gene, SRY, how it works, how it evolved and defined our sex chromosomes, well illustrates the value of comparing distantly related animals and the folly of relying on humans and mice for an understanding of the most fundamental aspects of mammalian biology. The 25th anniversary of the discovery of SRY seems a good time to review the contributions of Australian mammals to these discoveries.
The discovery of the mammalian sex determining gene, SRY, was a milestone in the history of human genetics. SRY opened up investigations into the pathway by which the genital ridge (bipotential gonad) becomes a testis. Studies of Australian mammals were important in the story of the discovery of SRY, not only in refuting the qualifications of the first candidate sex-determining gene, but also in confirming the ubiquity of SRY and raising questions as to how it works. Studies in marsupials also led to understanding of how SRY evolved from a gene on an autosome with functions in the brain and germ cells, and to identifying the ancestors of other genes on the human Y. The discovery that platypus have sex chromosomes homologous, not to the human XY, but to the bird ZW, dated the origin of the therian SRY and the XY chromosomes it defined. This led to important new models of how our sex chromosomes function, how they evolved, and what might befall this gene and the Y chromosome it defines.
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22
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Georges A, Li Q, Lian J, O'Meally D, Deakin J, Wang Z, Zhang P, Fujita M, Patel HR, Holleley CE, Zhou Y, Zhang X, Matsubara K, Waters P, Graves JAM, Sarre SD, Zhang G. High-coverage sequencing and annotated assembly of the genome of the Australian dragon lizard Pogona vitticeps. Gigascience 2015; 4:45. [PMID: 26421146 PMCID: PMC4585809 DOI: 10.1186/s13742-015-0085-2] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 09/14/2015] [Indexed: 11/10/2022] Open
Abstract
Background The lizards of the family Agamidae are one of the most prominent elements of the Australian reptile fauna. Here, we present a genomic resource built on the basis of a wild-caught male ZZ central bearded dragon Pogona vitticeps. Findings The genomic sequence for P. vitticeps, generated on the Illumina HiSeq 2000 platform, comprised 317 Gbp (179X raw read depth) from 13 insert libraries ranging from 250 bp to 40 kbp. After filtering for low-quality and duplicated reads, 146 Gbp of data (83X) was available for assembly. Exceptionally high levels of heterozygosity (0.85 % of single nucleotide polymorphisms plus sequence insertions or deletions) complicated assembly; nevertheless, 96.4 % of reads mapped back to the assembled scaffolds, indicating that the assembly included most of the sequenced genome. Length of the assembly was 1.8 Gbp in 545,310 scaffolds (69,852 longer than 300 bp), the longest being 14.68 Mbp. N50 was 2.29 Mbp. Genes were annotated on the basis of de novo prediction, similarity to the green anole Anolis carolinensis, Gallus gallus and Homo sapiens proteins, and P. vitticeps transcriptome sequence assemblies, to yield 19,406 protein-coding genes in the assembly, 63 % of which had intact open reading frames. Our assembly captured 99 % (246 of 248) of core CEGMA genes, with 93 % (231) being complete. Conclusions The quality of the P. vitticeps assembly is comparable or superior to that of other published squamate genomes, and the annotated P. vitticeps genome can be accessed through a genome browser available at https://genomics.canberra.edu.au. Electronic supplementary material The online version of this article (doi:10.1186/s13742-015-0085-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Qiye Li
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China ; Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, Copenhagen, 1350 Denmark
| | - Jinmin Lian
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China
| | - Denis O'Meally
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Janine Deakin
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Zongji Wang
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China ; School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006 China
| | - Pei Zhang
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China
| | - Matthew Fujita
- Department of Biology, University of Texas at Arlington, 701 S. Nedderman Drive, Arlington, TX 76019 USA
| | - Hardip R Patel
- John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601 Australia
| | - Clare E Holleley
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Yang Zhou
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China
| | - Xiuwen Zhang
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Kazumi Matsubara
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Paul Waters
- School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052 Australia
| | - Jennifer A Marshall Graves
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia ; School of Life Science, La Trobe University, Melbourne, VIC 3086 Australia
| | - Stephen D Sarre
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia
| | - Guojie Zhang
- China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China ; Centre for Social Evolution, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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23
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Badenhorst D, Hillier LW, Literman R, Montiel EE, Radhakrishnan S, Shen Y, Minx P, Janes DE, Warren WC, Edwards SV, Valenzuela N. Physical Mapping and Refinement of the Painted Turtle Genome (Chrysemys picta) Inform Amniote Genome Evolution and Challenge Turtle-Bird Chromosomal Conservation. Genome Biol Evol 2015; 7:2038-50. [PMID: 26108489 PMCID: PMC4524486 DOI: 10.1093/gbe/evv119] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2015] [Indexed: 01/04/2023] Open
Abstract
Comparative genomics continues illuminating amniote genome evolution, but for many lineages our understanding remains incomplete. Here, we refine the assembly (CPI 3.0.3 NCBI AHGY00000000.2) and develop a cytogenetic map of the painted turtle (Chrysemys picta-CPI) genome, the first in turtles and in vertebrates with temperature-dependent sex determination. A comparison of turtle genomes with those of chicken, selected nonavian reptiles, and human revealed shared and novel genomic features, such as numerous chromosomal rearrangements. The largest conserved syntenic blocks between birds and turtles exist in four macrochromosomes, whereas rearrangements were evident in these and other chromosomes, disproving that turtles and birds retain fully conserved macrochromosomes for greater than 300 Myr. C-banding revealed large heterochromatic blocks in the centromeric region of only few chromosomes. The nucleolar-organizing region (NOR) mapped to a single CPI microchromosome, whereas in some turtles and lizards the NOR maps to nonhomologous sex-chromosomes, thus revealing independent translocations of the NOR in various reptilian lineages. There was no evidence for recent chromosomal fusions as interstitial telomeric-DNA was absent. Some repeat elements (CR1-like, Gypsy) were enriched in the centromeres of five chromosomes, whereas others were widespread in the CPI genome. Bacterial artificial chromosome (BAC) clones were hybridized to 18 of the 25 CPI chromosomes and anchored to a G-banded ideogram. Several CPI sex-determining genes mapped to five chromosomes, and homology was detected between yet other CPI autosomes and the globally nonhomologous sex chromosomes of chicken, other turtles, and squamates, underscoring the independent evolution of vertebrate sex-determining mechanisms.
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Affiliation(s)
- Daleen Badenhorst
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University
| | | | - Robert Literman
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University
| | | | | | - Yingjia Shen
- The Genome Institute at Washington University, St Louis
| | - Patrick Minx
- The Genome Institute at Washington University, St Louis
| | - Daniel E Janes
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University Department of Organismic and Evolutionary Biology, Harvard University
| | | | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Harvard University
| | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University
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24
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Abstract
Dioecy (separate male and female individuals) ensures outcrossing and is more prevalent in animals than in plants. Although it is common in bryophytes and gymnosperms, only 5% of angiosperms are dioecious. In dioecious higher plants, flowers borne on male and female individuals are, respectively deficient in functional gynoecium and androecium. Dioecy is inherited via three sex chromosome systems: XX/XY, XX/X0 and WZ/ZZ, such that XX or WZ is female and XY, X0 or ZZ are males. The XX/XY system generates the rarer XX/X0 and WZ/ZZ systems. An autosome pair begets XY chromosomes. A recessive loss-of-androecium mutation (ana) creates X chromosome and a dominant gynoecium-suppressing (GYS) mutation creates Y chromosome. The ana/ANA and gys/GYS loci are in the sex-determining region (SDR) of the XY pair. Accumulation of inversions, deleterious mutations and repeat elements, especially transposons, in the SDR of Y suppresses recombination between X and Y in SDR, making Y labile and increasingly degenerate and heteromorphic from X. Continued recombination between X and Y in their pseudoautosomal region located at the ends of chromosomal arms allows survival of the degenerated Y and of the species. Dioecy is presumably a component of the evolutionary cycle for the origin of new species. Inbred hermaphrodite species assume dioecy. Later they suffer degenerate-Y-led population regression. Cross-hybridization between such extinguishing species and heterologous species, followed by genome duplication of segregants from hybrids, give rise to new species.
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25
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Mu Y, Zhao B, Tang WQ, Sun BJ, Zeng ZG, Valenzuela N, Du WG. Temperature-Dependent Sex Determination Ruled Out in the Chinese Soft-Shelled Turtle (Pelodiscus sinensis) via Molecular Cytogenetics and Incubation Experiments across Populations. Sex Dev 2015; 9:111-7. [DOI: 10.1159/000373903] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2014] [Indexed: 11/19/2022] Open
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26
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Gamble T, Coryell J, Ezaz T, Lynch J, Scantlebury DP, Zarkower D. Restriction Site-Associated DNA Sequencing (RAD-seq) Reveals an Extraordinary Number of Transitions among Gecko Sex-Determining Systems. Mol Biol Evol 2015; 32:1296-309. [DOI: 10.1093/molbev/msv023] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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27
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Schmid M, Steinlein C, Haaf T, Mijares-Urrutia A. Nascent ZW sex chromosomes in Thecadactylus rapicauda (Reptilia, Squamata, Phyllodactylidae). Cytogenet Genome Res 2014; 143:259-67. [PMID: 25247775 DOI: 10.1159/000366212] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2014] [Indexed: 11/19/2022] Open
Abstract
The chromosomes of the turnip-tailed gecko Thecadactylus rapicauda from the Falcón State in northern Venezuela were examined by means of conventional staining, a variety of banding techniques and in situ hybridization with an 18S + 28S rDNA probe. In female specimens, C-banding analyses detected a cryptic W sex chromosome-associated interstitial heterochromatic segment which is absent in the Z sex chromosome. These ZW sex chromosomes are considered to be in a nascent stage of morphological differentiation and are absent in T. rapicauda collected in Guatemala. The amount, location and fluorochrome affinities of constitutive heterochromatin, the position of the nucleolus organizer region, and the genome sizes of female and male individuals were determined. The previously published cytogenetic data on T. rapicauda are discussed.
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Affiliation(s)
- Michael Schmid
- Department of Human Genetics, Biocenter, University of Würzburg, Würzburg, Germany
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28
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Matsubara K, Gamble T, Matsuda Y, Zarkower D, Sarre SD, Georges A, Graves JAM, Ezaz T. Non-homologous sex chromosomes in two geckos (Gekkonidae: Gekkota) with female heterogamety. Cytogenet Genome Res 2014; 143:251-8. [PMID: 25227445 DOI: 10.1159/000366172] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/07/2014] [Indexed: 11/19/2022] Open
Abstract
Evaluating homology between the sex chromosomes of different species is an important first step in deducing the origins and evolution of sex-determining mechanisms in a clade. Here, we describe the preparation of Z and W chromosome paints via chromosome microdissection from the Australian marbled gecko (Christinus marmoratus) and their subsequent use in evaluating sex chromosome homology with the ZW chromosomes of the Kwangsi gecko (Gekko hokouensis) from eastern Asia. We show that the ZW sex chromosomes of C. marmoratus and G. hokouensis are not homologous and represent independent origins of female heterogamety within the Gekkonidae. We also show that the C. marmoratus Z and W chromosomes are genetically similar to each other as revealed by C-banding, comparative genomic hybridization, and the reciprocal painting of Z and W chromosome probes. This implies that sex chromosomes in C. marmoratus are at an early stage of differentiation, suggesting a recent origin.
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Affiliation(s)
- Kazumi Matsubara
- Institute for Applied Ecology, University of Canberra, Canberra, A.C.T., Australia
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Pokorná MJ, Rovatsos M, Kratochvíl L. Sex chromosomes and karyotype of the (nearly) mythical creature, the Gila monster, Heloderma suspectum (Squamata: Helodermatidae). PLoS One 2014; 9:e104716. [PMID: 25119263 PMCID: PMC4131918 DOI: 10.1371/journal.pone.0104716] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Accepted: 07/15/2014] [Indexed: 12/31/2022] Open
Abstract
A wide variety of sex determination systems exist among squamate reptiles. They can therefore serve as an important model for studies of evolutionary transitions among particular sex determination systems. However, we still have only a limited knowledge of sex determination in certain important lineages of squamates. In this respect, one of the most understudied groups is the family Helodermatidae (Anguimorpha) encompassing the only two venomous species of lizards which are potentially lethal to human beings. We uncovered homomorphic ZZ/ZW sex chromosomes in the Gila monster (Heloderma suspectum) with a highly heterochromatic W chromosome. The sex chromosomes are morphologically similar to the ZZ/ZW sex chromosomes of monitor lizards (Varanidae). If the sex chromosomes of helodermatids and varanids are homologous, female heterogamety may be ancestral for the whole Anguimorpha group. Moreover, we found that the karyotype of the Gila monster consists of 2n = 36 chromosomes (14 larger metacentric chromosomes and 22 acrocentric microchromosomes). 2n = 36 is the widely distributed chromosomal number among squamates. In his pioneering works representing the only previous cytogenetic examination of the family Helodermatidae, Matthey reported the karyotype as 2n = 38 and suggested a different chromosomal morphology for this species. We believe that this was probably erroneously. We also discovered a strong accumulation of telomeric sequences on several pairs of microchromosomes in the Gila monster, which is a trait documented relatively rarely in vertebrates. These new data fill an important gap in our understanding of the sex determination and karyotype evolution of squamates.
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Affiliation(s)
- Martina Johnson Pokorná
- Department of Ecology, Faculty of Science, Charles University in Prague, Praha, Czech Republic
- Institute of Animal Physiology and Genetics, Academy of the Sciences of the Czech Republic, Liběchov, Czech Republic
| | - Michail Rovatsos
- Department of Ecology, Faculty of Science, Charles University in Prague, Praha, Czech Republic
| | - Lukáš Kratochvíl
- Department of Ecology, Faculty of Science, Charles University in Prague, Praha, Czech Republic
- * E-mail:
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Deakin JE, Ezaz T. Tracing the evolution of amniote chromosomes. Chromosoma 2014; 123:201-16. [PMID: 24664317 PMCID: PMC4031395 DOI: 10.1007/s00412-014-0456-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/03/2014] [Accepted: 03/04/2014] [Indexed: 01/09/2023]
Abstract
A great deal of diversity in chromosome number and arrangement is observed across the amniote phylogeny. Understanding how this diversity is generated is important for determining the role of chromosomal rearrangements in generating phenotypic variation and speciation. Gaining this understanding is achieved by reconstructing the ancestral genome arrangement based on comparisons of genome organization of extant species. Ancestral karyotypes for several amniote lineages have been reconstructed, mainly from cross-species chromosome painting data. The availability of anchored whole genome sequences for amniote species has increased the evolutionary depth and confidence of ancestral reconstructions from those made solely from chromosome painting data. Nonetheless, there are still several key lineages where the appropriate data required for ancestral reconstructions is lacking. This review highlights the progress that has been made towards understanding the chromosomal changes that have occurred during amniote evolution and the reconstruction of ancestral karyotypes.
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Affiliation(s)
- Janine E Deakin
- Institute for Applied Ecology, University of Canberra, Canberra, 2601, Australia,
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Sequence and gene content of a large fragment of a lizard sex chromosome and evaluation of candidate sex differentiating gene R-spondin 1. BMC Genomics 2013; 14:899. [PMID: 24344927 PMCID: PMC3880147 DOI: 10.1186/1471-2164-14-899] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 12/13/2013] [Indexed: 12/23/2022] Open
Abstract
Background Scant genomic information from non-avian reptile sex chromosomes is available, and for only a few lizards, several snakes and one turtle species, and it represents only a small fraction of the total sex chromosome sequences in these species. Results We report a 352 kb of contiguous sequence from the sex chromosome of a squamate reptile, Pogona vitticeps, with a ZZ/ZW sex microchromosome system. This contig contains five protein coding genes (oprd1, rcc1, znf91, znf131, znf180), and major families of repetitive sequences with a high number of copies of LTR and non-LTR retrotransposons, including the CR1 and Bov-B LINEs. The two genes, oprd1 and rcc1 are part of a homologous syntenic block, which is conserved among amniotes. While oprd1 and rcc1 have no known function in sex determination or differentiation in amniotes, this homologous syntenic block in mammals and chicken also contains R-spondin 1 (rspo1), the ovarian differentiating gene in mammals. In order to explore the probability that rspo1 is sex determining in dragon lizards, genomic BAC and cDNA clones were mapped using fluorescence in situ hybridisation. Their location on an autosomal microchromosome pair, not on the ZW sex microchromosomes, eliminates rspo1 as a candidate sex determining gene in P. vitticeps. Conclusion Our study has characterized the largest contiguous stretch of physically mapped sex chromosome sequence (352 kb) from a ZZ/ZW lizard species. Although this region represents only a small fraction of the sex chromosomes of P. vitticeps, it has revealed several features typically associated with sex chromosomes including the accumulation of large blocks of repetitive sequences.
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Molecular cytogenetic map of the central bearded dragon, Pogona vitticeps (Squamata: Agamidae). Chromosome Res 2013; 21:361-74. [PMID: 23703235 DOI: 10.1007/s10577-013-9362-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Revised: 04/12/2013] [Accepted: 04/27/2013] [Indexed: 12/20/2022]
Abstract
Reptiles, as the sister group to birds and mammals, are particularly valuable for comparative genomic studies among amniotes. The Australian central bearded dragon (Pogona vitticeps) is being developed as a reptilian model for such comparisons, with whole-genome sequencing near completion. The karyotype consists of 6 pairs of macrochromosomes and 10 pairs microchromosomes (2n = 32), including a female heterogametic ZW sex microchromosome pair. Here, we present a molecular cytogenetic map for P. vitticeps comprising 87 anchor bacterial artificial chromosome clones that together span each macro- and microchromosome. It is the first comprehensive cytogenetic map for any non-avian reptile. We identified an active nucleolus organizer region (NOR) on the sub-telomeric region of 2q by mapping 18S rDNA and Ag-NOR staining. We identified interstitial telomeric sequences in two microchromosome pairs and the W chromosome, indicating that microchromosome fusion has been a mechanism of karyotypic evolution in Australian agamids within the last 21 to 19 million years. Orthology searches against the chicken genome revealed an intrachromosomal rearrangement of P. vitticeps 1q, identified regions orthologous to chicken Z on P. vitticeps 2q, snake Z on P. vitticeps 6q and the autosomal microchromosome pair in P. vitticeps orthologous to turtle Pelodiscus sinensis ZW and lizard Anolis carolinensis XY. This cytogenetic map will be a valuable reference tool for future gene mapping studies and will provide the framework for the work currently underway to physically anchor genome sequences to chromosomes for this model Australian squamate.
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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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Strong conservation of the bird Z chromosome in reptilian genomes is revealed by comparative painting despite 275 million years divergence. Chromosoma 2011; 120:455-68. [PMID: 21725690 DOI: 10.1007/s00412-011-0322-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 04/18/2011] [Accepted: 04/25/2011] [Indexed: 01/20/2023]
Abstract
The divergence of lineages leading to extant squamate reptiles (lizards, snakes, and amphisbaenians) and birds occurred about 275 million years ago. Birds, unlike squamates, have karyotypes that are typified by the presence of a number of very small chromosomes. Hence, a number of chromosome rearrangements might be expected between bird and squamate genomes. We used chromosome-specific DNA from flow-sorted chicken (Gallus gallus) Z sex chromosomes as a probe in cross-species hybridization to metaphase spreads of 28 species from 17 families representing most main squamate lineages and single species of crocodiles and turtles. In all but one case, the Z chromosome was conserved intact despite very ancient divergence of sauropsid lineages. Furthermore, the probe painted an autosomal region in seven species from our sample with characterized sex chromosomes, and this provides evidence against an ancestral avian-like system of sex determination in Squamata. The avian Z chromosome synteny is, therefore, conserved albeit it is not a sex chromosome in these squamate species.
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Patel VS, Ezaz T, Deakin JE, Graves JAM. Globin gene structure in a reptile supports the transpositional model for amniote α- and β-globin gene evolution. Chromosome Res 2010; 18:897-907. [PMID: 21116705 DOI: 10.1007/s10577-010-9164-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 10/20/2010] [Accepted: 10/21/2010] [Indexed: 10/18/2022]
Abstract
The haemoglobin protein, required for oxygen transportation in the body, is encoded by α- and β-globin genes that are arranged in clusters. The transpositional model for the evolution of distinct α-globin and β-globin clusters in amniotes is much simpler than the previously proposed whole genome duplication model. According to this model, all jawed vertebrates share one ancient region containing α- and β-globin genes and several flanking genes in the order MPG-C16orf35-(α-β)-GBY-LUC7L that has been conserved for more than 410 million years, whereas amniotes evolved a distinct β-globin cluster by insertion of a transposed β-globin gene from this ancient region into a cluster of olfactory receptors flanked by CCKBR and RRM1. It could not be determined whether this organisation is conserved in all amniotes because of the paucity of information from non-avian reptiles. To fill in this gap, we examined globin gene organisation in a squamate reptile, the Australian bearded dragon lizard, Pogona vitticeps (Agamidae). We report here that the α-globin cluster (HBK, HBA) is flanked by C16orf35 and GBY and is located on a pair of microchromosomes, whereas the β-globin cluster is flanked by RRM1 on the 3' end and is located on the long arm of chromosome 3. However, the CCKBR gene that flanks the β-globin cluster on the 5' end in other amniotes is located on the short arm of chromosome 5 in P. vitticeps, indicating that a chromosomal break between the β-globin cluster and CCKBR occurred at least in the agamid lineage. Our data from a reptile species provide further evidence to support the transpositional model for the evolution of β-globin gene cluster in amniotes.
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Affiliation(s)
- Vidushi S Patel
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
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Sex chromosome evolution in amniotes: applications for bacterial artificial chromosome libraries. J Biomed Biotechnol 2010; 2011:132975. [PMID: 20981143 PMCID: PMC2957134 DOI: 10.1155/2011/132975] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 09/27/2010] [Indexed: 11/18/2022] Open
Abstract
Variability among sex chromosome pairs in amniotes denotes a dynamic history. Since amniotes diverged from a common ancestor, their sex chromosome pairs and, more broadly, sex-determining mechanisms have changed reversibly and frequently. These changes have been studied and characterized through the use of many tools and experimental approaches but perhaps most effectively through applications for bacterial artificial chromosome (BAC) libraries. Individual BAC clones carry 100–200 kb of sequence from one individual of a target species that can be isolated by screening, mapped onto karyotypes, and sequenced. With these techniques, researchers have identified differences and similarities in sex chromosome content and organization across amniotes and have addressed hypotheses regarding the frequency and direction of past changes. Here, we review studies of sex chromosome evolution in amniotes and the ways in which the field of research has been affected by the advent of BAC libraries.
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Non-homologous sex chromosomes of birds and snakes share repetitive sequences. Chromosome Res 2010; 18:787-800. [DOI: 10.1007/s10577-010-9152-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 08/04/2010] [Accepted: 08/04/2010] [Indexed: 11/26/2022]
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Davis JK, Thomas PJ, Thomas JW. A W-linked palindrome and gene conversion in New World sparrows and blackbirds. Chromosome Res 2010; 18:543-53. [PMID: 20535633 DOI: 10.1007/s10577-010-9134-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/10/2010] [Accepted: 05/10/2010] [Indexed: 10/19/2022]
Abstract
A hallmark feature of the male-specific region of the human Y chromosome is the presence of large and near-identical palindromes. These palindromes are maintained in a state of near identity via gene conversion between the arms of the palindrome, and both neutral and selection-based theories have been proposed to explain their enrichment on the human Y and X chromosomes. While those proposed theories would be applicable to sex chromosomes in other species, it has not been established whether near-identical palindromes are a common feature of sex chromosomes in a broader range of taxa, including other tetrapods. Here, we report the genomic sequencing and features of a 279-kb region of the non-recombining portion of the W chromosome spanning the CHD1W locus in a New World sparrow, the white-throated sparrow (Zonotrichia albicollis), and the corresponding region on the Z chromosome. As has been observed for other Y and W chromosomes, we detected a high repetitive element content (51%) and low gene content on the white-throated sparrow W chromosome. In addition, we identified a 22-kb near-identical (>99%) palindrome on the W chromosome that flanks the 5' end of the CHD1W gene. Signatures of gene conversion were readily detected between the arms of this palindrome, as was the presence of this palindrome in other New World sparrows and blackbirds. Near-identical palindromes are therefore present on the avian W chromosome and may persist due to the same forces proposed for the enrichment of these elements on the human sex chromosomes.
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Affiliation(s)
- Jamie K Davis
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA
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Marshall Graves JA, Peichel CL. Are homologies in vertebrate sex determination due to shared ancestry or to limited options? Genome Biol 2010; 11:205. [PMID: 20441602 PMCID: PMC2884537 DOI: 10.1186/gb-2010-11-4-205] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The same candidate genes and the same autosomes are repeatedly used as sex chromosomes in vertebrates. Are these systems identical by descent, or are some genes or chromosomes intrinsically better at triggering the first steps of sex determination?
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