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3,457 results for “chromosomes”
The genetic mechanism of B chromosome drive in rye illuminated by chromosomescale assembly
<p>Figures, tables and supplementary data from the paper: The genetic mechanism of B chromosome drive in rye illuminated by chromosomescale assembly<br><br>Abstract: The genomes of many plants, animals, and fungi frequently comprise dispensable B chromosomes that rely upon various chromosomal drive mechanisms to counteract the tendency of non-essential genetic elements to be purged over time. The B chromosome of rye – a model system for nearly a century – undergoes targeted nondisjunction during first pollen mitosis, favouring segregation into the generative nucleus, thus increasing their numbers over generations. However, the genetic mechanisms underlying this process are poorly understood. Here, using a newly-assembled, ~430Mb-long rye B chromosome pseudomolecule, we identify five candidate genes whose role as trans-acting moderators of the chromosomal drive is supported by karyotyping, chromosome drive analysis and comparative RNA-seq. Among them, we identify DCR28, coding a microtubule-associated protein related to cell division, and detect this gene also in the B chromosome of Aegilops speltoides. The DCR28 gene family is neo-functionalised and serially-duplicated with 15 B chromosome-located copies that are uniquely highly expressed in the first pollen mitosis of rye.</p>
Source Data: Visualization of chromosomal reorganization induced by heterologous fusions in the mammalian nucleus
<p>Source data from Visualization of chromosomal reorganization induced by heterologous fusions in the mammalian nucleus</p>
Chromosome Numbers and Reproductive Life Cycles in Green Plants: A phylo-transcriptomic perspective
<p>The supplemental dataset for "Chromosome Numbers and Reproductive Life Cycles in Green Plants: A phylo-transcriptomic perspective."</p>
Cell-cycle dependent DNA repair and replication unifies patterns of chromosome instability
<p>This repository contains the data used to generate the figures in paper: Cell-cycle dependent DNA repair and replication unifies patterns of chromosome instability.</p>
Heterogeneous histories of recombination suppression on stickleback sex chromosomes
<p>How consistent are the evolutionary trajectories of sex chromosomes shortly after they form? Insights into the evolution of recombination, differentiation, and degeneration can be provided by comparing closely related species with homologous sex chromosomes. The sex chromosomes of the threespine stickleback (<em>Gasterosteus aculeatus</em>) and its sister species, the Japan Sea stickleback (<em>G. nipponicus)</em>, have been well characterized. Little is known, however, about the sex chromosomes of their congener, the blackspotted stickleback (<em>G. wheatlandi</em>). We used pedigrees to obtain experimentally phased whole genome sequences from blackspotted stickleback X and Y chromosomes. Using multispecies gene trees and analysis of shared duplications, we demonstrate that Chromosome 19 is the ancestral sex chromosome and that its oldest stratum evolved in the common ancestor of the genus. After the blackspotted lineage diverged, its sex chromosomes experienced independent and more extensive recombination suppression, greater X-Y differentiation, and a much higher rate of Y degeneration than the other two species. These patterns may result from a smaller effective population size in the blackspotted stickleback. A recent fusion between the ancestral blackspotted stickleback Y chromosome and Chromosome 12, which produced a neo-X and neo-Y, may have been favored by the very small size of the recombining region on the ancestral sex chromosome. We identify six strata on the ancestral and neo-sex chromosomes where recombination between the X and Y ceased at different times. These results confirm that sex chromosomes can evolve large differences within and between species over short evolutionary timescales.</p>
Tspe_v1 (Telopea speciosissima) genome supplementary files for: Chromosome-level de novo genome assembly of Telopea speciosissima (New South Wales waratah) using long-reads, linked-reads and Hi-C
<p><i>Telopea speciosissima, </i>the New South Wales waratah, is an Australian endemic woody shrub in the family Proteaceae. Waratahs have great potential as a model clade to better understand processes of speciation, introgression and adaptation, and are significant from a horticultural perspective. Here, we report the first chromosome-level genome for <i>T. speciosissima</i>. Combining Oxford Nanopore long-reads, 10x Genomics Chromium linked-reads and Hi-C data, the assembly spans 823 Mb (scaffold N50 of 69.0 Mb) with 97.8 % of Embryophyta BUSCOs 'Complete'. We present a new method in Diploidocus (<a href="https://github.com/slimsuite/diploidocus">https://github.com/slimsuite/diploidocus</a>) for classifying, curating and QC-filtering scaffolds, which combines read depths, <i>k</i>-mer frequencies and BUSCO predictions. We also present a new tool, DepthSizer (<a href="https://github.com/slimsuite/depthsizer">https://github.com/slimsuite/depthsizer</a>), for genome size estimation from the read depth of single-copy orthologues and estimate the genome size to be approximately 900 Mb. The largest 11 scaffolds contained 94.1 % of the assembly, conforming to the expected number of chromosomes (2<i>n</i> = 22). Genome annotation predicted 40,158<code> </code>protein-coding genes, 351 rRNAs and 728 tRNAs. We investigated <i>CYCLOIDEA </i>(<i>CYC</i>)<i> </i>genes, which have a role in determination of floral symmetry, and confirm the presence of two copies in the genome. Read depth analysis of 180 'Duplicated' BUSCO genes using a new tool, DepthKopy (<a href="https://github.com/slimsuite/depthkopy">https://github.com/slimsuite/depthkopy</a>), suggests almost all are real duplications, increasing confidence in the annotation and highlighting a possible need to revise the BUSCO set for this lineage. The chromosome-level <i>T. speciosissima</i> reference genome (Tspe_v1) provides an important new genomic resource of Proteaceae to support the conservation of flora in Australia and further afield.</p>
Non-centrosomal microtubules at kinetochores promote rapid chromosome biorientation during mitosis in human cells
<p>Kinetochore tracking data associated with "Non-centrosomal microtubules at kinetochores promote rapid chromosome biorientation during mitosis in human cells" by Renda, Miles, et al., Current Biology, 2022.</p> <p>Contact Alexey Khodjakov at alexey.khodjakov@health.ny.gov for any questions or processing routines.</p> <p>Each file contains coordinates of centrioles and kinetochores in a single cell. </p> <p>Key to variables:</p> <p>ao -- time point corresponding to anaphase onset</p> <p>cell_id -- comprises three parts: cell type_treatment_number (NaN when only first 15 min of prometaphase were tracked).</p> <p>centrioles -- coordinates of centrioles. Two pages correspond to the two centrosomes, first three columns are X-Y-Z of the mother and the second three columns are X-Y-Z of the daughter centrioles</p> <p>kinetochores -- coordinates of kinetochores. Each page corresponds to a chromosome. X-Y-Z coordinates of sister kinetochores are in columns 1-3 and 4-6.</p> <p>neb -- time point corresponding to nuclear envelope breakdown.</p> <p>total_chrs -- number of chromosomes in the cell</p> <p>tracked -- number of tracks obtained in the cell</p>
De novo assembly of 20 chicken genomes reveals the undetectable phenomenon for thousands of core genes on micro-chromosomes and sub-telomeric regions
<p>The gene numbers and evolutionary rates of birds were assumed to be much lower than those of mammals, which is in sharp contrast to the huge species number and morphological diversity of birds. It is therefore necessary to construct a complete avian genome and analyze its evolution. We constructed a chicken pan-genome from 20 <em>de novo</em> assembled genomes with high sequencing depth, and identified 1,335 protein-coding genes and 3,011 long noncoding RNAs not found in GRCg6a. The majority of these novel genes were detected across most individuals of the examined transcriptomes but were seldomly measured in each of the DNA sequencing data regardless of Illumina or PacBio technology. Furthermore, different from previous pan-genome models, most of these novel genes were overrepresented on chromosomal sub-telomeric regions and micro-chromosomes, surrounded by extremely high proportions of tandem repeats, which strongly blocks DNA sequencing. These hidden genes were proved to be shared by all chicken genomes, included many housekeeping genes, and enriched in immune pathways. Comparative genomics revealed the novel genes had three-fold elevated substitution rates than known ones, updating the knowledge about evolutionary rates in birds. Our study provides a framework for constructing a better chicken genome, which will contribute towards the understanding of avian evolution and improvement of poultry breeding.</p>
Arabidopsis thaliana Col-CEN complete Chromosome 2 numt sequences and alignments
<p>Data associated with the assembly of complete chromosome 2 nuclear insertion of mitochondrial DNA (numt) from the <em>Arabidopsis thaliana</em> accession Columbia (Col-CEN). A full report of this project can be obtained in a manuscript titled "<strong>Complete sequence of a 641-kb insertion of mitochondrial DNA in the <em>Arabidopsis thaliana </em>nuclear genome</strong>".</p>
RPE-1 GFP-H2B iCas9 sgFBXW7-A cell undergoing mitosis with a lagging chromosome that forms a micronucleus
<p>Zeiss AxioObserver video showing an RPE-1 GFP-H2B iCas9 sgFBXW7-A cell undergoing mitosis with a lagging chromosome that forms a micronucleus. Cells were treated with 1 μg/mL doxycycline for 96 hours to induce Cas9 expression and were imaged every 2 minutes for 24 hours at 40x magnification. At 15:44 chromosomes begin to condense (prophase); at 16:04 chromosomes begin to align on the metaphase plate (prometaphase); at 16:10 the chromosomes are aligned (metaphase); at 16:12 chromosomes are pulled to opposite poles of the cell (anaphase) and the lagging chromosome can be seen above the separating chromosomes; at 16:18 the chromosomes begin to unravel (telophase) and the lagging chromosome can be seen on the left-hand side of the chromosomes of the left daughter cell; from 16:28 onwards the lagging chromosome forms a micronucleus next to the nucleus of the daughter cell.</p>
Data from: Identification of selection signals on the X-chromosome in East Adriatic sheep: a new complementary approach
<p>Sheep are one of the most important livestock species in Croatia, found mainly in the Mediterranean coastal and mountainous regions along the East Adriatic coast, well adapted to the environment and mostly kept extensively. Our main objective was therefore to map the positive selection of the X-chromosome (18,983 SNPs that passed quality control), since nothing is known about the adaptation genes on this chromosome for any of the breeds from the Balkan cluster. Analyses were performed on a sample of eight native Croatian breeds (101 females and 100 males) representing the East Adriatic metapopulation and on 10 mouflons (five females and males), all sampled in Croatia. Three classical within-population approaches (extreme Runs of Homozygosity islands, integration Haplotype Scores, and number of Segregating Sites by Length) were applied along with our new approach called Haplotype Richness Drop (HRiD), which uses only the information contained in male haplotypes. We have also shown that phylogenetic analyses, such as the Median-joining network, can provide additional information when performed with the selection signals identified by HRiD. Our new approach identifies positive selection signals by searching for genomic regions that exhibit a sudden decline in haplotype richness. In total, we identified 14 positive selection signals, 11 using the classical approach and three using the HRiD approach, all together containing 34 annotated genes. High repeatability (86%) of results was observed, as 12 identified selection signals were also confirmed in other studies with sheep. HRiD offers an interesting possibility to be used complementary to other approaches or when only males are genotyped, which is often the case in genomic breeding value estimations. These results highlight the importance of the X-chromosome in the adaptive architecture of domestic ruminants, while our novel HRiD approach opens new possibilities for research.</p>
Data and code from: Multiple sex chromosome drivers in a mammal with three sex chromosomes
<p><span>Eukaryotes with separate males and females display a great diversity in the way they determine sex, but it is still unclear what evolutionary forces cause transitions between sex-determining systems. Rather that the lack of hypotheses, the problem is the scarcity of adequate biological systems to test them. Here, we take advantage of the recent evolution of a feminizing X chromosome (called X*) in the African pygmy mouse <em>Mus minutoides</em>, to investigate one of the evolutionary forces hypothesized to cause such transitions, namely sex chromosome drive (i.e., biased transmission of sex chromosomes to the next generation). Through extensive molecular sexing of pups at weaning, we reveal the existence of a remarkable male sex chromosome drive system in this species, whereby direction and strength of drive is conditional upon the genotype of males' partners: males transmit their Y at a rate close to 80% when mating with XX or XX* females, and only 36% when mating with X*Y females. Using mathematical modelling, we explore the joint evolution of these unusual sex-determining and drive systems, revealing that different sequences of events could have led to the evolution of this bizarre system, and that the "conditional" nature of sex chromosome drive plays a crucial role in the short- and long-term maintenance of the three sex chromosomes.</span></p>
Chromosome communities in the human pangenome
<p>Results of the analysis of the acrocentric chromosome community in the human pangenome. The plots were presented at the T2T/HPRC assembly meeting on May 9th, 2022.</p>
Unique structure and positive selection promote the rapid divergence of Drosophila Y chromosomes
Y chromosomes across diverse species convergently evolve a gene-poor, heterochromatic organization enriched for duplicated genes, LTR retrotransposons, and satellite DNA. Sexual antagonism and a loss of recombination play major roles in the degeneration of young Y chromosomes. However, the processes shaping the evolution of mature, already degenerated Y chromosomes are less well-understood. Because Y chromosomes evolve rapidly, comparisons between closely related species are particularly useful. We generated de novo long read assemblies complemented with cytological validation to reveal Y chromosome organization in three closely related species of the Drosophila simulans complex, which diverged only 250,000 years ago and share >98% sequence identity. We find these Y chromosomes are divergent in their organization and repetitive DNA composition and discover new Y-linked gene families whose evolution is driven by both positive selection and gene conversion. These Y chromosomes are also enriched for large deletions, suggesting that the repair of double-strand breaks on Y chromosomes may be biased toward microhomology-mediated end joining over canonical non-homologous end-joining. We propose that this repair mechanism contributes to the convergent evolution of Y chromosome organization across organisms.
A chromosome-scale genome assembly of the okapi (Okapia johnstoni)
<p><span>The okapi (<em>Okapia johnstoni</em>), or forest giraffe, is the only species in its genus and the only extant sister group of the giraffe within the family Giraffidae. The species is one of the remaining large vertebrates surrounded by mystery because of its elusive behavior as well as the armed conflicts in the region where it occurs, making it difficult to study. Deforestation puts the okapi under constant anthropogenic pressure, and it is currently listed as "Endangered" on the IUCN Red List. Here, we present the first annotated de novo okapi genome assembly based on PacBio continuous long reads, polished with short reads, and anchored into chromosome-scale scaffolds using Hi-C proximity ligation sequencing. The final assembly (TBG_Okapi_asm_v1) has a length of 2.39 Gbp, of which 98% are represented by 28 scaffolds >3.9 Mbp. The contig N50 of 61 Mbp and scaffold N50 of 102 Mbp, together with a BUSCO score of 94.7%, and 23,412 annotated genes, underline the high quality of the assembly. This chromosome-scale genome assembly is a valuable resource for future conservation of the species and comparative genomic studies among the giraffids and other ruminants.</span></p>
A single genomic region involving a putative chromosome rearrangement in flat oyster (Ostrea edulis) is associated with differential host resilience to the parasite Bonamia ostreae
<p>European flat oyster (<em>Ostrea edulis</em>) is an ecologically and economically important marine bivalve, that has been severely affected by the intracellular parasite <em>Bonamia ostreae</em>. In this study, a flat oyster SNP array (~14,000 SNPs) was used to validate previously reported outlier loci for divergent selection associated with <em>B. ostreae</em> exposure in the Northeast Atlantic Area. A total of 134 wild and hatchery individuals from the North Sea, collected in naïve (NV) and long-term affected (LTA) areas, were analysed. Genetic diversity and differentiation were related to the sampling origin (wild vs hatchery) when using neutral markers, and to bonamiosis status (NV vs LTA) when using outlier loci for divergent selection. Two genetic clusters appeared intermingled in all sampling locations when using outlier loci and their frequency was associated with their bonamiosis status. When both clusters were compared, outlier datasets showed high genetic divergence (FST > 0.25) unlike neutral loci (FST not ≠ 0). Moreover, the cluster associated with LTA samples showed much higher genetic diversity and significant heterozygote excess with outlier loci, but not with neutral data. Most outliers mapped on chromosome 8 (OE-C8) of the flat oyster genome, supporting a main genomic region underlying resilience to bonamiosis. Furthermore, differentially expressed genes previously reported between NV and LTA strains showed higher mapping density on OE-C8. A range of relevant immune functions were specifically enriched among genes annotated on OE-C8, providing hypotheses for resilience mechanisms to an intracellular parasite. The results suggest that marker-assisted selection could be applied to breed resilient strains of <em>O. edulis</em> to bonamiosis, if lower parasite load and/or higher viability of the LTA genetic cluster following <em>B. ostreae</em> infection is demonstrated.</p>
Synapsed homologs of meiotic mouse chromosomes visualized by TIRFM
<p>Mouse testes were removed from euthanized animals, followed by decapsulation and maceration in high-glucose MEM medium. Suspension was mixed thoroughly and left to settle; the supernatant was then collected and centrifuged at 7200 rpm for 1 min. The pellet was then resuspended in a 0.5 M sucrose solution and added to PFA-treated (1% in 0.015% Triton X-100) coverslides, which were incubated for at room temperature for 2 hours in a humidified environment. After incubation, slides were rinsed twice with a wetting agent solution (Kodak, 1464510) in water and allowed to air dry. SYCP3 was labeled with primary SCP-3 (D-1) antibody (Santa Cruz Biotechnology, SC-74569) and a secondary anti-mouse antibody fused with Alexa-568 (Thermo, A11004). Surface chromosome spreads were imaged in an Elyra 7 microscope (Zeiss), with a 60x 1.4 NA oil immersion objective and an a 1.4x magnification lens. Image reconstruction was performed in ZEN Black with parameters set to default.</p> <p>Experimental procedures were approved by the “Ministero della Salute" of Italy, authorization n.701/2018-PR.</p>
Data for: New insights into Xenopus sex chromosome genomics from the Marsabit clawed frog, X. borealis
<p><span>In many groups, sex chromosomes change frequently but the drivers of their rapid evolution are varied and often poorly characterized. With an aim of further understanding sex chromosome turnover, we investigated the polymorphic sex chromosomes of the Marsabit clawed frog, <em>Xenopus borealis,</em> using genomic data and a new chromosome-scale genome assembly. We confirmed previous findings that 54.1 Mb of chromosome 8L is sex-linked in animals from east Kenya and a lab strain, but most (or all) of this region is not sex-linked in natural populations from west Kenya. Previous work suggests possible degeneration of the Z chromosomes in the east population because many sex-linked transcripts of this female heterogametic population have female-biased expression, and we therefore expected this chromosome to not be present in the west population. In contrast, our simulations support a model where the sex-linked portion of the Z chromosome from the east acquired autosomal segregation in the west, and where the W chromosome from the east was lost in the west. These recent changes are consistent with the hot potato model, wherein sex chromosome turnover is favoured by natural selection if it purges a (minimally) degenerate sex-specific sex chromosome, but counterintuitively suggest natural selection failed to purge a Z chromosome that has signs of more advanced and possibly more ancient regulatory degeneration. These findings highlight complex evolutionary dynamics of young, rapidly evolving <em>Xenopus</em> sex chromosomes, and set the stage for mechanistic work aimed at pinpointing additional sex-determining genes in this group.</span></p>
A chromosome-level genome assembly of the highly heterozygous sea urchin Echinometra sp. EZ reveals adaptation in the regulatory regions of stress response genes
<p><em>Echinometra</em> is the most widespread genus of sea urchin and has been the focus of a wide range of studies in ecology, speciation, and reproduction. However, available genetic data for this genus are generally limited to a few select loci. Here, we present a chromosome-level genome assembly based on 10x Genomics, PacBio, and Hi-C sequencing for <em>Echinometra</em> sp. EZ from the Persian/Arabian Gulf. The genome is assembled into 210 scaffolds totaling 817.8 Mb with an N50 of 39.5 Mb. From this assembly we determined that the <em>E</em>. sp. EZ genome consists of 2n = 42 chromosomes. BUSCO analysis showed that 95.3% of BUSCO genes were complete. ab initio and transcript-informed gene modeling and annotation identified 29,<span>405</span> genes, including a conserved Hox cluster. <em>E.</em> sp. EZ can be found in high-temperature and high-salinity environments, and we therefore compared gene families and transcription factors associated with environmental stress response ("defensome") with other echinoid species with similar high-quality genomic resources. While the number of defensome genes was broadly similar for all species, we identified strong signatures of positive selection in non-coding elements near genes involved in environmental response pathways as well as losses of transcriptions factors important for environmental response. These data provide key insights into the biology of <em>E</em>. sp. EZ as well as the diversification of <em>Echinometra</em> more widely and will serve as a useful tool for the community to explore questions in this taxonomic group and beyond.</p>
A novel neo-sex chromosome in Sylvietta brachyura (Macrosphenidae) adds to the extraordinary avian sex chromosome diversity among Sylvioidea songbirds
<p><span>We report the discovery of a novel neo-sex chromosome in an African warbler, <em>Sylvietta brachyura</em> (northern crombec; Macrosphenidae). This species is part of the Sylvioidea superfamily, where four separate autosome–sex chromosome translocation events have previously been discovered via comparative genomics of 11 of the 22 families in this clade. Our discovery here resulted from analyses of genomic data of single-species representatives from three additional Sylvioidea families (Macrosphenidae, Pycnonotidae, and Leiothrichidae). In all three species, we confirmed the translocation of a part of chromosome 4A to the sex chromosomes, which originated basally in Sylvioidea. In <em>S. brachyura</em>, we found that a part of chromosome 8 has been translocated to the sex chromosomes, forming a unique neo-sex chromosome in this lineage. Furthermore, the non-recombining part of 4A in <em>S. brachyura</em> is smaller than in other Sylvioidea species which suggests that recombination continued along this region after the fusion event in the Sylvioidea ancestor. These findings reveal additional sex chromosome diversity among the Sylvioidea, where five separate translocation events are now confirmed.</span></p>
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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.