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375 results for “X* chromosome”
Data from: Limited evidence for extensive genetic differentiation between X and Y chromosomes in Hybognathus amarus (Cypriniformes:Leuciscidae)
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Data from: Mapping reduced introgression loci to the X chromosome of the hybridizing field crickets, Gryllus firmus and G. pennsylvanicus
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Data from: Identification of selection signals on the X-chromosome in East Adriatic sheep: a new complementary approach
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The X chromosome of insects likely predates the origin of Class Insecta
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X chromosome drive is constrained by sexual selection and influences ornament evolution
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Dynamic evolution of euchromatic satellites on the X chromosome in Drosophila melanogaster and the simulans clade
ABSTRACTSatellite DNAs (satDNAs) are among the most dynamically evolving components of eukaryotic genomes and play important roles in genome regulation, genome evolution, and speciation. Despite their abundance and functional impact, we know little about the evolutionary dynamics and molecular mechanisms that shape satDNA distributions in genomes. Here we use high-quality genome assemblies to study evolutionary dynamics of two complex satDNAs, Rsp-like and 1.688 gm/cm3, in Drosophila melanogaster and its three nearest relatives in the simulans clade. We show that large blocks of these repeats are highly dynamic in the heterochromatin, where their genomic location varies across species. We discovered that small blocks of satDNA that are abundant in X chromosome euchromatin are similarly dynamic, with repeats changing in abundance, location, and composition among species. We detail the proliferation of a rare satellite (Rsp-like) across the X chromosome in D. simulans and D. mauritiana. Rsp-like spreads by inserting into existing clusters of the older, more abundant 1.688 satellite, in events that were likely facilitated by microhomology-mediated repair pathways. We show that Rsp-like is abundant on extrachromosomal circular DNA in D. simulans, which may have contributed to its dynamic evolution. Intralocus satDNA expansions via unequal exchange and the movement of higher-order repeats also contribute to the fluidity of the repeat landscape. We find evidence that euchromatic satDNA repeats experience cycles of proliferation and diversification somewhat analogous to bursts of transposable element proliferation. Our study lays a foundation for mechanistic studies of satDNA proliferation and the functional and evolutionary consequences of satDNA movement.
Data from: The last bastion? X chromosome genotyping of Anopheles gambiae species pair males from a hybrid zone reveals complex recombination within the major candidate 'genomic island of speciation'
Speciation with gene flow may be aided by reduced recombination helping to build linkage between genes involved in the early stages of reproductive isolation. Reduced recombination on chromosome X has been implicated in speciation within the Anopheles gambiae complex, species of which represent the major Afrotropical malaria vectors. The most recently diverged, morphologically indistinguishable, species pair, A. gambiae and Anopheles coluzzii, ubiquitously displays a 'genomic island of divergence' spanning over 4 Mb from chromosome X centromere, which represents a particularly promising candidate region for reproductive isolation genes, in addition to containing the diagnostic markers used to distinguish the species. Very low recombination makes the island intractable for experimental recombination studies, but an extreme hybrid zone in Guinea Bissau offers the opportunity for natural investigation of X-island recombination. SNP analysis of chromosome X hemizygous males revealed: (i) strong divergence in the X-island despite a lack of autosomal divergence; (ii) individuals with multiple-recombinant genotypes, including likely double crossovers and localized gene conversion; (iii) recombination-driven discontinuity both within and between the molecular species markers, suggesting that the utility of the diagnostics is undermined under high hybridization. The largely, but incompletely protected nature of the X centromeric genomic island is consistent with a primary candidate area for accumulation of adaptive variants driving speciation with gene flow, while permitting some selective shuffling and removal of genetic variation.
Data from: A rare exception to Haldane's rule: Are X chromosomes key to hybrid incompatibilities?
The prevalence of Haldane's rule suggests that sex chromosomes commonly have a key role in reproductive barriers and speciation. However, the majority of research on Haldane's rule has been conducted in species with conventional sex determination systems (XY and ZW) and exceptions to the rule have been understudied. Here we test the role of X-linked incompatibilities in a rare exception to Haldane's rule for female sterility in field cricket sister species (Teleogryllus oceanicus and T. commodus). Both have an XO sex determination system. Using three generations of crosses, we introgressed X chromosomes from each species onto different, mixed genomic backgrounds to test predictions about the fertility and viability of each cross type. We predicted that females with two different species X chromosomes would suffer reduced fertility and viability compared with females with two parental X chromosomes. However, we found no strong support for such X-linked incompatibilities. Our results preclude X–X incompatibilities and instead support an interchromosomal epistatic basis to hybrid female sterility. We discuss the broader implications of these findings, principally whether deviations from Haldane's rule might be more prevalent in species without dimorphic sex chromosomes.
Data from: The large-X effect in plants: increased species divergence and reduced gene flow on the Silene X-chromosome
The disproportionately large involvement of the X-chromosome in the isolation of closely related species (the large-X effect) has been reported for many animals, where X-linked genes are mostly hemizygous in the heterogametic sex. The expression of deleterious recessive mutations is thought to drive the frequent involvement of the X-chromosome in hybrid sterility, as well as to reduce interspecific gene flow for X-linked genes. Here, we evaluate the role of the X-chromosome in the speciation of two closely related plant species – the white and red campions (Silene latifolia and S. dioica) – that hybridize widely across Europe. The two species evolved separate sexes and sex chromosomes relatively recently (~107 years), and unlike most animal species, most X-linked genes have intact Y-linked homologs. We demonstrate that the X-linked genes show a very small and insignificant amount of interspecific gene flow, while gene flow involving autosomal loci is significant and sufficient to homogenise the gene pools of the two species. These findings are consistent with the hypothesis of the large-X effect in Silene and comprise the first report of this effect in plants. Non-hemizygosity of many X-linked genes in Silene males indicates that exposure of recessive mutations to selection may not be essential for the occurrence of the large-X effect. Several possible causes of the large-X effect in Silene are discussed.
Autosomal suppression and fitness costs of an old driving X chromosome in Drosophila testacea
<p>Driving X chromosomes (X<sup>D</sup>s) are meiotic drivers that bias their own transmission through males by killing Y-bearing gametes. These chromosomes can in theory spread rapidly in populations and cause extinction, but many are found as balanced polymorphisms or as "cryptic" X<sup>D</sup>s shut down by drive suppressors. The relative likelihood of these outcomes, as well as the evolutionary pathways through which they come about, are not well-understood. An X<sup>D</sup> was recently discovered in the mycophagous fly, <em>Drosophila testacea</em>, presenting the opportunity to compare this X<sup>D</sup> with the well-studied X<sup>D</sup> of its sister species, <em>Drosophila neotestacea</em>. Comparing features of independently evolved X<sup>D</sup>s in young sister species is a promising avenue towards understanding how X<sup>D</sup>s and their counter acting forces change over time. In contrast to the X<sup>D</sup> of <em>D. neotestacea</em>, we find that the X<sup>D</sup> of <em>D. testacea</em> is old, with its origin predating the radiation of three species: <em>D. testacea</em>, <em>D. neotestacea</em>, and their shared sister species, <em>Drosophila orientacea</em>. Motivated by the suggestion that older X<sup>D</sup>s should be more deleterious to carriers, we assessed the effect of the X<sup>D</sup> on both male and female fertility. Unlike what is known from <em>D. neotestacea</em>, we found a strong fitness cost in females homozygous for the X<sup>D</sup> in <em>D. testacea</em>: a large proportion of homozygous females failed to produce offspring after being housed with males for several days. Our male fertility experiments show that while X<sup>D</sup> male fertility is lower under sperm depleting conditions, X<sup>D</sup> males have comparable fertility to males carrying a standard X chromosome under a free mating regime, which may better approximate conditions in wild populations of <em>D. testacea</em>. Lastly, we demonstrate the presence of autosomal suppression of X chromosome drive. Our results provide support for a model of X<sup>D</sup> evolution where the dynamics of young X<sup>D</sup>s are governed by fitness consequences in males, whereas in older X<sup>D</sup> systems, both suppression and fitness consequences in females likely supersede male fitness costs.</p>
FIGURES 16–21. Endecous ubajarensis n in A new species of Endecous Saussure, 1878 (Orthoptera, Gryllidae) from northeast Brazil with the first X X 0 chromosomal sex system in Gryllidae
FIGURES 16–21. Endecous ubajarensis n. sp. female UBA02. 16—subgenital plate; 17—supranal plate; 18—ovipositor, ventral view; 19—ovipositor, lateral view; 20—ovipositor apex, dorsal view; 21—ovipositor apex, lateral view.
FIGURES 12–15. Endecous ubajarensis n in A new species of Endecous Saussure, 1878 (Orthoptera, Gryllidae) from northeast Brazil with the first X X 0 chromosomal sex system in Gryllidae
FIGURES 12–15. Endecous ubajarensis n. sp. phallic sclerites of the paratype UBA03. 12—dorsal view; 13—ventral view; 14—diagonal view; 15—posterior view. Conventions: Ps.Arm—pseudepiphallic arm; Ps.db—pseudepiphallic dorsal branch; Ps.vb—pseudepiphallic ventral branch; Ps.P—pseudepiphallic paramere; Ps.ib—Pseudepiphallic sclerite inner bars; Ps.mspseudepiphallic membranous shield; Ect.Arc—ectophallic arc; Ect.lb—ectophallic lateral bar; Ect.mp—ectophallic median projection; Ect.Ap—ectophallic apodeme; End.Sc.a—endophallic sclerite anterior portion; End.Sc.p—endophallic sclerite posterior portion.
FIGURES 3–11. Endecous ubajarensis n in A new species of Endecous Saussure, 1878 (Orthoptera, Gryllidae) from northeast Brazil with the first X X 0 chromosomal sex system in Gryllidae
FIGURES 3–11. Endecous ubajarensis n. sp. holotype morphology. 3–5—habitus in lateral, dorsal, and ventral views, respectively; 6—head, frontal view; 7—supranal-plate; 8—subgenital plate; 9a, b, c—tibia III outer apical spurs; arrow, distal subapical spur; 10d, e, f, g—inner apical spurs; 11—tibia and tarsus, lateral view; arrow, distal subapical spur.
3D chromatin structures associated with ncRNA roX2 for hyperactivation and co-activation across the entire X chromosome
<p>The SMLM datasets of roX2 and roX2/H3K27me3.</p>
X-chromosome Inactivation, Epigenetics and the Transcriptome
ClinicalTrials.gov study NCT01678261. IPD Sharing: Not stated. Countries: 1. Publications: 2.
Dynamic evolution of euchromatic satellites on the X chromosome in Drosophila melanogaster and the simulans clade
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Data from: Empirical evidence for large X-effects in animals with undifferentiated sex chromosomes
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Population genetic recursions to model-biased X chromosome inactivation
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Data from: The last bastion? X chromosome genotyping of Anopheles gambiae species pair males from a hybrid zone reveals complex recombination within the major candidate ‘genomic island of speciation’
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Autosomal suppression and fitness costs of an old driving X chromosome in Drosophila testacea
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.