Subjects -> BIOLOGY (Total: 3174 journals)
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BIOLOGY (1491 journals)            First | 1 2 3 4 5 6 7 8 | Last

Showing 201 - 400 of 1720 Journals sorted alphabetically
Biological Research     Open Access   (Followers: 1)
Biological Rhythm Research     Hybrid Journal   (Followers: 1)
Biological Theory     Hybrid Journal   (Followers: 3)
Biological Trace Element Research     Hybrid Journal  
Biologicals     Full-text available via subscription   (Followers: 7)
Biologics: Targets & Therapy     Open Access   (Followers: 1)
Biologie Aujourd'hui     Full-text available via subscription  
Biologie in Unserer Zeit (Biuz)     Hybrid Journal   (Followers: 36)
Biologija     Open Access  
Biology     Open Access   (Followers: 3)
Biology and Philosophy     Hybrid Journal   (Followers: 18)
Biology Bulletin     Hybrid Journal   (Followers: 1)
Biology Bulletin Reviews     Hybrid Journal  
Biology Direct     Open Access   (Followers: 9)
Biology Letters     Full-text available via subscription   (Followers: 44)
Biology Methods and Protocols     Open Access  
Biology of Sex Differences     Open Access   (Followers: 1)
Biology of the Cell     Full-text available via subscription   (Followers: 9)
Biology Open     Open Access  
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Bioma : Jurnal Ilmiah Biologi     Open Access  
Biomacromolecules     Hybrid Journal   (Followers: 23)
Biomarker Insights     Open Access   (Followers: 2)
Biomarkers     Hybrid Journal   (Followers: 4)
Biomass and Bioenergy     Partially Free   (Followers: 8)
Biomaterials     Hybrid Journal   (Followers: 55)
Biomaterials Advances     Full-text available via subscription   (Followers: 19)
Biomath     Open Access  
Biomatter     Open Access  
Biomechanics and Modeling in Mechanobiology     Hybrid Journal   (Followers: 8)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomedical Engineering     Hybrid Journal   (Followers: 11)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 11)
BioMedical Engineering OnLine     Open Access   (Followers: 4)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 4)
Biomedical Journal     Open Access   (Followers: 5)
Biomedical Science and Engineering     Open Access   (Followers: 5)
Biomedical Signal Processing and Control     Hybrid Journal   (Followers: 9)
BioMetals     Hybrid Journal   (Followers: 1)
Biometrical Letters     Open Access  
Biometrics     Hybrid Journal   (Followers: 51)
Biometrika     Hybrid Journal   (Followers: 21)
Biomimetic Intelligence and Robotics     Open Access  
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
Biomolecules     Open Access   (Followers: 1)
BioNanoScience     Partially Free   (Followers: 3)
Bionature     Open Access   (Followers: 1)
Biopreservation and Biobanking     Hybrid Journal   (Followers: 2)
Bioprocess and Biosystems Engineering     Hybrid Journal   (Followers: 9)
Bioresource Technology     Partially Free   (Followers: 9)
BioRisk     Open Access   (Followers: 2)
Biosaintifika : Journal of Biology & Biology Education     Open Access  
BioScience     Hybrid Journal   (Followers: 27)
Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science     Hybrid Journal   (Followers: 3)
Biosemiotics     Hybrid Journal   (Followers: 1)
Biosensors     Open Access   (Followers: 3)
Biosensors and Bioelectronics     Hybrid Journal   (Followers: 27)
Biosensors and Bioelectronics : X     Open Access   (Followers: 2)
Bioseparation     Hybrid Journal   (Followers: 1)
Biosfer : Jurnal Biologi dan Pendidikan Biologi     Open Access  
Biosfer : Jurnal Tadris Biologi     Open Access  
BioSocieties     Hybrid Journal   (Followers: 3)
Biospecies     Open Access  
BIOspektrum     Hybrid Journal   (Followers: 5)
Biostatistics     Hybrid Journal   (Followers: 18)
Biosystematics and Ecology     Open Access   (Followers: 2)
Biosystems     Hybrid Journal   (Followers: 3)
Biosystems Diversity     Open Access  
Biota Amazônia     Open Access  
Biota Neotropica     Open Access  
Biotechnology Advances     Hybrid Journal   (Followers: 34)
Biotropia : The Southeast Asian Journal of Tropical Biology     Open Access  
Biotropica     Hybrid Journal   (Followers: 19)
Birth Defects Research     Hybrid Journal  
BJHM Open Research     Full-text available via subscription  
BMC Bioinformatics     Open Access   (Followers: 109)
BMC Biology     Open Access   (Followers: 50)
BMC Developmental Biology     Open Access   (Followers: 13)
BMC Evolutionary Biology     Open Access   (Followers: 58)
BMC Genomics     Open Access   (Followers: 69)
BMC Molecular and Cell Biology     Open Access   (Followers: 40)
BMC Proceedings     Full-text available via subscription   (Followers: 2)
BMC Research Notes     Open Access   (Followers: 3)
BMC Structural Biology     Open Access   (Followers: 8)
BMC Systems Biology     Open Access   (Followers: 16)
Boletín Científico : Centro de Museos. Museo de Historia Natural     Open Access  
Boletín del Centro de Investigaciones Biológicas     Open Access  
Boletín Micológico     Open Access  
Bone Reports     Open Access  
Bonorowo Wetlands     Open Access  
Borneo Journal of Resource Science and Technology     Open Access  
Bothalia : African Biodiversity & Conservation     Open Access  
Brain Science Advances     Open Access  
Brazilian Journal of Biological Sciences     Open Access  
Breastfeeding Medicine     Hybrid Journal   (Followers: 20)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 43)
Briefings in Functional Genomics     Hybrid Journal   (Followers: 3)
British Poultry Abstracts     Hybrid Journal   (Followers: 3)
Brittonia     Hybrid Journal  
Bulletin de la Société Royale des Sciences de Liège     Open Access  
Bulletin of Experimental Biology and Medicine     Hybrid Journal  
Bulletin of Mathematical Biology     Hybrid Journal   (Followers: 9)
Bulletin of the Ecological Society of America     Open Access   (Followers: 4)
Bulletin of the Lebedev Physics Institute     Hybrid Journal  
Butlletí de la Institució Catalana d'Història Natural     Open Access  
CABI Agriculture and Bioscience     Open Access   (Followers: 1)
Caldasia     Open Access  
Cameroon Journal of Experimental Biology     Open Access  
Canadian Journal of Bioethics     Open Access  
Canadian Journal of Plant Pathology     Hybrid Journal   (Followers: 3)
Çanakkale Onsekiz Mart University Journal of Marine Sciences and Fisheries     Open Access  
Cancer Biology & Therapy     Open Access   (Followers: 11)
Cancer Cell International     Open Access   (Followers: 7)
Carbon Capture Science & Technology     Open Access  
Carbon Management     Hybrid Journal   (Followers: 5)
Carbon Resources Conversion     Open Access   (Followers: 2)
Caryologia : International Journal of Cytology, Cytosystematics and Cytogenetics     Partially Free  
Caucasiana     Open Access  
Cell     Full-text available via subscription   (Followers: 1136)
Cell Adhesion & Migration     Open Access   (Followers: 9)
Cell and Tissue Banking     Hybrid Journal   (Followers: 1)
Cell and Tissue Biology     Hybrid Journal   (Followers: 4)
Cell and Tissue Research     Hybrid Journal   (Followers: 5)
Cell Biochemistry and Function     Hybrid Journal   (Followers: 8)
Cell Biology and Development     Open Access   (Followers: 2)
Cell Biology and Toxicology     Hybrid Journal   (Followers: 10)
Cell Biology Education     Free   (Followers: 4)
Cell Biology International     Hybrid Journal   (Followers: 4)
Cell Biology International Reports     Hybrid Journal   (Followers: 2)
Cell Calcium     Hybrid Journal   (Followers: 2)
Cell Communication & Adhesion     Hybrid Journal   (Followers: 2)
Cell Cycle     Full-text available via subscription   (Followers: 5)
Cell Death and Differentiation     Hybrid Journal   (Followers: 7)
Cell Discovery     Open Access   (Followers: 2)
Cell Division     Open Access   (Followers: 1)
Cell Genomics     Full-text available via subscription   (Followers: 2)
Cell Metabolism     Full-text available via subscription   (Followers: 58)
Cell Proliferation     Open Access  
Cell Reports     Open Access   (Followers: 61)
Cell Reports Medicine     Open Access   (Followers: 3)
Cell Reports Methods     Open Access   (Followers: 1)
Cell Research     Hybrid Journal   (Followers: 11)
Cell Stress and Chaperones     Hybrid Journal   (Followers: 1)
Cell Surface     Open Access  
Cell Systems     Hybrid Journal   (Followers: 7)
Cells     Open Access   (Followers: 2)
Cells & Development     Hybrid Journal   (Followers: 3)
Cells Tissues Organs     Full-text available via subscription   (Followers: 1)
Cellular Immunology     Hybrid Journal   (Followers: 29)
Cellular Logistics     Full-text available via subscription  
Cellular Microbiology     Hybrid Journal   (Followers: 12)
Cellular Oncology     Hybrid Journal   (Followers: 3)
Cellular Reprogramming     Hybrid Journal  
Cellular Signalling     Hybrid Journal   (Followers: 10)
Ceylon Journal of Science     Open Access  
Channels     Open Access   (Followers: 1)
Check List : The Journal of Biodiversity Data     Open Access   (Followers: 2)
Chem     Hybrid Journal  
ChemBioEng Reviews     Full-text available via subscription   (Followers: 3)
Chemosensory Perception     Hybrid Journal  
Chirality     Hybrid Journal  
Chromosoma     Hybrid Journal  
Chromosome Research     Hybrid Journal   (Followers: 2)
Ciencia     Open Access  
Ciencia Amazónica (Iquitos)     Open Access  
Ciência ET Praxis     Open Access  
CienciaUAT     Open Access  
Cladistics     Hybrid Journal   (Followers: 7)
Climate Change Ecology     Open Access   (Followers: 14)
Clinical Dysmorphology     Hybrid Journal  
Clinical Phytoscience     Open Access  
Clinical Proteomics     Open Access   (Followers: 3)
Clinical Spectroscopy     Open Access  
Coevolution     Open Access  
Cogent Biology     Open Access  
Cognitive Neurodynamics     Hybrid Journal   (Followers: 2)
Cold Spring Harbor Perspectives in Biology     Full-text available via subscription   (Followers: 3)
Cold Spring Harbor Protocols     Full-text available via subscription   (Followers: 4)
Communication in Biomathematical Sciences     Open Access   (Followers: 2)
Communications Biology     Open Access  
Communications in Applied Sciences     Open Access  
Communications Materials     Open Access  
Communicative & Integrative Biology     Open Access  
Community Ecology     Full-text available via subscription   (Followers: 27)
Comparative Medicine     Full-text available via subscription   (Followers: 5)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comptes Rendus : Chimie     Open Access  
Comptes Rendus Biologies     Open Access   (Followers: 1)
Computational Biology Journal     Open Access   (Followers: 6)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 5)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 10)
Computer Methods in Biomechanics and Biomedical Engineering : Imaging & Visualization     Hybrid Journal  
Computers in Biology and Medicine     Hybrid Journal   (Followers: 11)
Connective Tissue Research     Hybrid Journal  
Contact (CTC)     Open Access  
Contributions to Plasma Physics     Hybrid Journal   (Followers: 3)
CRISPR Journal     Hybrid Journal  
Critical Reviews in Clinical Laboratory Sciences     Hybrid Journal   (Followers: 19)
Crustaceana     Hybrid Journal   (Followers: 6)
Cryobiology     Hybrid Journal   (Followers: 3)

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Chromosoma
Journal Prestige (SJR): 2.678
Citation Impact (citeScore): 4
Number of Followers: 0  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1432-0886 - ISSN (Online) 0009-5915
Published by Springer-Verlag Homepage  [2469 journals]
  • Allele segregation analysis of F1 hybrids between independent Brassica
           allohexaploid lineages

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      Abstract: Abstract In the Brassica genus, we find both diploid species (one genome) and allotetraploid species (two different genomes) but no naturally occurring hexaploid species (three different genomes, AABBCC). Although hexaploids can be produced via human intervention, these neo-polyploids have quite unstable genomes and usually suffer from severe genome reshuffling. Whether these genome rearrangements continue in later generations and whether genomic arrangements follow similar, reproducible patterns between different lineages is still unknown. We crossed Brassica hexaploids resulting from different species combinations to produce five F1 hybrids and analyzed the karyotypes of the parents and the F1 hybrids, as well as allele segregation in a resulting test-cross population via molecular karyotyping using SNP array genotyping. Although some genomic regions were found to be more likely to be duplicated, deleted, or rearranged, a consensus pattern was not shared between genotypes. Brassica hexaploids had a high tolerance for fixed structural rearrangements, but which rearrangements occur and become fixed over many generations does not seem to show either strong reproducibility or to indicate selection for stability. On average, we observed 10 de novo chromosome rearrangements contributed almost equally from both parents to the F1 hybrids. At the same time, the F1 hybrid meiosis produced on average 8.6 new rearrangements. Hence, the increased heterozygosity in the F1 hybrid did not significantly improve genome stability in our hexaploid hybrids and might have had the opposite effect. However, hybridization between lineages was readily achieved and may be exploited for future genetics and breeding purposes.
      PubDate: 2022-05-05
       
  • Life of double minutes: generation, maintenance, and elimination

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      Abstract: Abstract Advances in genome sequencing have revealed a type of extrachromosomal DNA, historically named double minutes (also referred to as ecDNA), to be common in a wide range of cancer types, but not in healthy tissues. These cancer-associated circular DNA molecules contain one or a few genes that are amplified when double minutes accumulate. Double minutes harbor oncogenes or drug resistance genes that contribute to tumor aggressiveness through copy number amplification in combination with favorable epigenetic properties. Unequal distribution of double minutes over daughter cells contributes to intratumoral heterogeneity, thereby increasing tumor adaptability. In this review, we discuss various models delineating the mechanism of generation of double minutes. Furthermore, we highlight how double minutes are maintained, how they evolve, and discuss possible mechanisms driving their elimination.
      PubDate: 2022-04-30
       
  • Kinesin-5 Eg5 mediates centrosome separation to control spindle assembly
           in spermatocytes

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      Abstract: Abstract Timely and accurate centrosome separation is critical for bipolar spindle organization and faithful chromosome segregation during cell division. Kinesin-5 Eg5 is essential for centrosome separation and spindle organization in somatic cells; however, the detailed functions and mechanisms of Eg5 in spermatocytes remain unclear. In this study, we show that Eg5 proteins are located at spindle microtubules and centrosomes in spermatocytes both in vivo and in vitro. We reveal that the spermatocytes are arrested at metaphase I in seminiferous tubules after Eg5 inhibition. Eg5 ablation results in cell cycle arrest, the formation of monopolar spindle, and chromosome misalignment in cultured GC-2 spd cells. Importantly, we find that the long-term inhibition of Eg5 results in an increased number of centrosomes and chromosomal instability in spermatocytes. Our findings indicate that Eg5 mediates centrosome separation to control spindle assembly and chromosome alignment in spermatocytes, which finally contribute to chromosome stability and faithful cell division of the spermatocytes.
      PubDate: 2022-04-18
       
  • Germline-restricted chromosome shows remarkable variation in size among
           closely related passerine species

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      Abstract: Abstract Passerine birds have a supernumerary chromosome in their germ cells called the germline-restricted chromosome (GRC). The GRC was first discovered more than two decades ago in zebra finch but recent studies have suggested that it is likely present in all passerines, the most species rich avian order, encompassing more than half of all modern bird species. Despite its wide taxonomic distribution, studies on this chromosome are still scarce and limited to a few species. Here, we cytogenetically analyzed the GRC in five closely related estrildid finch species of the genus Lonchura. We show that the GRC varies enormously in size, ranging from a tiny micro-chromosome to one of the largest macro-chromosomes in the cell, not only among recently diverged species but also within species and sometimes even between germ cells of a single individual. In Lonchura atricapilla, we also observed variation in GRC copy number among male germ cells of a single individual. Finally, our analysis of hybrids between two Lonchura species with noticeably different GRC size directly supported maternal inheritance of the GRC. Our results reveal the extraordinarily dynamic nature of the GRC, which might be caused by frequent gains and losses of sequences on this chromosome leading to substantial differences in genetic composition of the GRC between and even within species. Such differences might theoretically contribute to reproductive isolation between species and thus accelerate the speciation rate of passerine birds compared to other bird lineages.
      PubDate: 2022-04-07
       
  • Multiple heterochromatin diversification events in the genome of
           fungus-farming ants: insights from repetitive sequences

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      Abstract: Abstract A substantial portion of the eukaryotic genome includes repetitive DNA, which is important for its stability, regulation, and architecture. Fungus-farming ant genomes show remarkable structural rearrangement rates that were necessary for the establishment of their agriculture-based lifestyle, highlighting the relevance of this peculiar group in understanding the repetitive portion of ant genome. Chromosomal banding studies are in accordance with genomic data because they show that repetitive heterochromatic sequences of basal and derivative Attina species are GC-rich, an uncommon trait in Formicidae. To understand the evolutionary dynamics of heterochromatin in Attina, we compared GC-rich heterochromatin patterns between the Paleoattina and Neoattina clades of this subtribe. To this end, we hybridized the Mrel-C0t probe (highly and moderately repetitive DNA) obtained from Mycetomoellerius relictus, Neoattina with GC-rich heterochromatin, in karyotypes of Paleoattina and Neoattina species. Additionally, we mapped the repetitive sequences (GA)15 and (TTAGG)6 in species of the two clades to investigate their organization and evolutionary patterns in the genome of Attina. The Mrel-C0t probe marked the heterochromatin in M. relictus, in other Mycetomoellerius spp., and in species of Mycetarotes, Cyphomyrmex, and Sericomyrmex (Neoattina). In Mycetomoellerius urichii, only pericentromeric heterochromatin was marked with Mrel-C0t. No marking was observed in Paleoattina species or in Atta and Acromyrmex (Neoattina). These results indicated that different evolutionary events led to heterochromatin differentiation in Attina. The most likely hypothesis is that GC-rich heterochromatin arose in the common ancestor of the two clades and accumulated various changes throughout evolution. The sequences (GA)15 and (TTAGG)6 located in euchromatin and telomeres, respectively, showed more homogeneous results among the species.
      PubDate: 2022-03-24
       
  • The N-terminal domain of TET1 promotes the formation of dense chromatin
           regions refractory to transcription

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      Abstract: Abstract TET (ten-eleven translocation) enzymes initiate active cytosine demethylation via the oxidation of 5-methylcytosine. TET1 is composed of a C-terminal domain, which bears the catalytic activity of the enzyme, and a N-terminal region that is less well characterized except for the CXXC domain responsible for the targeting to CpG islands. While cytosine demethylation induced by TET1 promotes transcription, this protein also interacts with chromatin-regulating factors that rather silence this process, the coordination between these two opposite functions of TET1 being unclear. In the present work, we uncover a new function of the N-terminal part of the TET1 protein in the regulation of the chromatin architecture. This domain of the protein promotes the establishment of a compact chromatin architecture displaying reduced exchange rate of core histones and partial dissociation of the histone linker. This chromatin reorganization process, which does not rely on the CXXC domain, is associated with a global shutdown of transcription and an increase in heterochromatin-associated histone epigenetic marks. Based on these findings, we propose that the dense chromatin organization generated by the N-terminal domain of TET1 could contribute to restraining the transcription enhancement induced by the DNA demethylation activity of this enzyme.
      PubDate: 2022-03-02
      DOI: 10.1007/s00412-022-00769-0
       
  • Satellitome analysis illuminates the evolution of ZW sex chromosomes of
           Triportheidae fishes (Teleostei: Characiformes)

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      Abstract: Abstract Satellites are an abundant source of repetitive DNAs that play an essential role in the chromosomal organization and are tightly linked with the evolution of sex chromosomes. Among fishes, Triportheidae stands out as the only family where almost all species have a homeologous ZZ/ZW sex chromosomes system. While the Z chromosome is typically conserved, the W is always smaller, with variations in size and morphology between species. Here, we report an analysis of the satellitome of Triportheus auritus (TauSat) by integrating genomic and chromosomal data, with a special focus on the highly abundant and female-biased satDNAs. In addition, we investigated the evolutionary trajectories of the ZW sex chromosomes in the Triportheidae family by mapping satDNAs in selected representative species of this family. The satellitome of T. auritus comprised 53 satDNA families of which 24 were also hybridized by FISH. Most satDNAs differed significantly between sexes, with 19 out of 24 being enriched on the W chromosome of T. auritus. The number of satDNAs hybridized into the W chromosomes of T. signatus and T. albus decreased to six and four, respectively, in accordance with the size of their W chromosomes. No TauSat probes produced FISH signals on the chromosomes of Agoniates halecinus. Despite its apparent conservation, our results indicate that each species differs in the satDNA accumulation on the Z chromosome. Minimum spanning trees (MSTs), generated for three satDNA families with different patterns of FISH mapping data, revealed different homogenization rates between the Z and W chromosomes. These results were linked to different levels of recombination between them. The most abundant satDNA family (TauSat01) was exclusively hybridized in the centromeres of all 52 chromosomes of T. auritus, and its putative role in the centromere evolution was also highlighted. Our results identified a high differentiation of both ZW chromosomes regarding satellites composition, highlighting their dynamic role in the sex chromosomes evolution.
      PubDate: 2022-01-31
      DOI: 10.1007/s00412-022-00768-1
       
  • NucPosDB: a database of nucleosome positioning in vivo and nucleosomics of
           cell-free DNA

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      Abstract: Abstract Nucleosome positioning is involved in many gene regulatory processes happening in the cell, and it may change as cells differentiate or respond to the changing microenvironment in a healthy or diseased organism. One important implication of nucleosome positioning in clinical epigenetics is its use in the “nucleosomics” analysis of cell-free DNA (cfDNA) for the purpose of patient diagnostics in liquid biopsies. The rationale for this is that the apoptotic nucleases that digest chromatin of the dying cells mostly cut DNA between nucleosomes. Thus, the short pieces of DNA in body fluids reflect the positions of nucleosomes in the cells of origin. Here, we report a systematic nucleosomics database — NucPosDB — curating published nucleosome positioning datasets in vivo as well as datasets of sequenced cell-free DNA (cfDNA) that reflect nucleosome positioning in situ in the cells of origin. Users can select subsets of the database by a number of criteria and then obtain raw or processed data. NucPosDB also reports the originally determined regions with stable nucleosome occupancy across several individuals with a given condition. An additional section provides a catalogue of computational tools for the analysis of nucleosome positioning or cfDNA experiments and theoretical algorithms for the prediction of nucleosome positioning preferences from DNA sequence. We provide an overview of the field, describe the structure of the database in this context, and demonstrate data variability using examples of different medical conditions. NucPosDB is useful both for the analysis of fundamental gene regulation processes and the training of computational models for patient diagnostics based on cfDNA. The database currently curates ~ 400 publications on nucleosome positioning in cell lines and in situ as well as cfDNA from > 10,000 patients and healthy volunteers. For open-access cfDNA datasets as well as key MNase-seq datasets in human cells, NucPosDB allows downloading processed mapped data in addition to the regions with stable nucleosome occupancy. NucPosDB is available at https://generegulation.org/nucposdb/.
      PubDate: 2022-01-21
      DOI: 10.1007/s00412-021-00766-9
       
  • Incorporation of CENP-A/CID into centromeres during early Drosophila
           

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      Abstract: Abstract In many species, centromere identity is specified epigenetically by special nucleosomes containing a centromere-specific histone H3 variant, designated as CENP-A in humans and CID in Drosophila melanogaster. After partitioning of centromere-specific nucleosomes onto newly replicated sister centromeres, loading of additional CENP-A/CID into centromeric chromatin is required for centromere maintenance in proliferating cells. Analyses with cultured cells have indicated that transcription of centromeric DNA by RNA polymerase II is required for deposition of new CID into centromere chromatin. However, a dependence of centromeric CID loading on transcription is difficult to reconcile with the notion that the initial embryonic stages appear to proceed in the absence of transcription in Drosophila, as also in many other animal species. To address the role of RNA polymerase II–mediated transcription for CID loading in early Drosophila embryos, we have quantified the effects of alpha-amanitin and triptolide on centromeric CID-EGFP levels. Our analyses demonstrate that microinjection of these two potent inhibitors of RNA polymerase II–mediated transcription has at most a marginal effect on centromeric CID deposition during progression through the early embryonic cleavage cycles. Thus, we conclude that at least during early Drosophila embryogenesis, incorporation of CID into centromeres does not depend on RNA polymerase II–mediated transcription.
      PubDate: 2022-01-11
      DOI: 10.1007/s00412-022-00767-2
       
  • The life and times of the nucleus

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      PubDate: 2021-12-01
      DOI: 10.1007/s00412-021-00765-w
       
  • The extensive amplification of heterochromatin in Melipona bees revealed
           by high throughput genomic and chromosomal analysis

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      Abstract: Abstract Satellite DNAs (satDNAs) and transposable elements (TEs) are among the main components of constitutive heterochromatin (c-heterochromatin) and are related to their functionality, dynamics, and evolution. A peculiar case regarding the quantity and distribution of c-heterochromatin is observed in the genus of bees, Melipona, with species having a low amount of heterochromatin and species with high amount occupying almost all chromosomes. By combining low-pass genome sequencing and chromosomal analysis, we characterized the satDNAs and TEs of Melipona quadrifasciata (low c-heterochromatin) and Melipona scutellaris (high low c-heterochromatin) to understand c-heterochromatin composition and evolution. We identified 15 satDNA families and 20 TEs for both species. Significant variations in the repeat landscapes were observed between the species. In M. quadrifasciata, the repetitive fraction corresponded to only 3.78% of the genome library studied, whereas in M. scutellaris, it represented 54.95%. Massive quantitative and qualitative changes contributed to the differential amplification of c-heterochromatin, mainly due to the amplification of exclusive repetitions in M. scutellaris, as the satDNA MscuSat01-195 and the TE LTR/Gypsy_1 that represent 38.20 and 14.4% of its genome, respectively. The amplification of these two repeats is evident at the chromosomal level, with observation of their occurrence on most c-heterochromatin. Moreover, we detected repeats shared between species, revealing that they experienced mainly quantitative variations and varied in the organization on chromosomes and evolutionary patterns. Together, our data allow the discussion of patterns of evolution of repetitive DNAs and c-heterochromatin that occurred in a short period of time, after separation of the Michmelia and Melipona subgenera.
      PubDate: 2021-12-01
      DOI: 10.1007/s00412-021-00764-x
       
  • Heterologous synapsis in C. elegans is regulated by meiotic double-strand
           breaks and crossovers

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      Abstract: Abstract Alignment of the parental chromosomes during meiotic prophase is key to the formation of genetic exchanges, or crossovers, and consequently to the successful production of gametes. In almost all studied organisms, alignment involves synapsis: the assembly of a conserved inter-chromosomal interface called the synaptonemal complex (SC). While the SC usually synapses homologous sequences, it can assemble between heterologous sequences. However, little is known about the regulation of heterologous synapsis. Here, we study the dynamics of heterologous synapsis in the nematode C. elegans. We characterize two experimental scenarios: SC assembly onto a folded-back chromosome that cannot pair with its homologous partner; and synapsis of pseudo-homologs, a fusion chromosome partnering with an unfused chromosome half its size. We observed elevated levels of heterologous synapsis when the number of meiotic double-strand breaks or crossovers were reduced, indicating that the promiscuity of synapsis is regulated by break formation or repair. In addition, our data suggests the existence of both chromosome-specific and nucleus-wide regulation on heterologous synapsis.
      PubDate: 2021-10-04
      DOI: 10.1007/s00412-021-00763-y
       
  • Linear elements are stable structures along the chromosome axis in fission
           yeast meiosis

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      Abstract: Abstract The structure of chromosomes dramatically changes upon entering meiosis to ensure the successful progression of meiosis-specific events. During this process, a multilayer proteinaceous structure called a synaptonemal complex (SC) is formed in many eukaryotes. However, in the fission yeast Schizosaccharomyces pombe, linear elements (LinEs), which are structures related to axial elements of the SC, form on the meiotic cohesin-based chromosome axis. The structure of LinEs has been observed using silver-stained electron micrographs or in immunofluorescence-stained spread nuclei. However, the fine structure of LinEs and their dynamics in intact living cells remain to be elucidated. In this study, we performed live cell imaging with wide-field fluorescence microscopy as well as 3D structured illumination microscopy (3D-SIM) of the core components of LinEs (Rec10, Rec25, Rec27, Mug20) and a linE-binding protein Hop1. We found that LinEs form along the chromosome axis and elongate during meiotic prophase. 3D-SIM microscopy revealed that Rec10 localized to meiotic chromosomes in the absence of other LinE proteins, but shaped into LinEs only in the presence of all three other components, the Rec25, Rec27, and Mug20. Elongation of LinEs was impaired in double-strand break-defective rec12− cells. The structure of LinEs persisted after treatment with 1,6-hexanediol and showed slow fluorescence recovery from photobleaching. These results indicate that LinEs are stable structures resembling axial elements of the SC.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00757-w
       
  • Sex differences in the meiotic behavior of an XX sex chromosome pair in
           males and females of the mole vole Ellobius tancrei: turning an X into a Y
           chromosome'

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      Abstract: Abstract Sex determination in mammals is usually provided by a pair of chromosomes, XX in females and XY in males. Mole voles of the genus Ellobius are exceptions to this rule. In Ellobius tancrei, both males and females have a pair of XX chromosomes that are indistinguishable from each other in somatic cells. Nevertheless, several studies on Ellobius have reported that the two X chromosomes may have a differential organization and behavior during male meiosis. It has not yet been demonstrated if these differences also appear in female meiosis. To test this hypothesis, we have performed a comparative study of chromosome synapsis, recombination, and histone modifications during male and female meiosis in E. tancrei. We observed that synapsis between the two X chromosomes is limited to the short distal (telomeric) regions of the chromosomes in males, leaving the central region completely unsynapsed. This uneven behavior of sex chromosomes during male meiosis is accompanied by structural modifications of one of the X chromosomes, whose axial element tends to appear fragmented, accumulates the heterochromatin mark H3K9me3, and is associated with a specific nuclear body that accumulates epigenetic marks and proteins such as SUMO-1 and centromeric proteins but excludes others such as H3K4me, ubiH2A, and γH2AX. Unexpectedly, sex chromosome synapsis is delayed in female meiosis, leaving the central region unsynapsed during early pachytene. This region accumulates γH2AX up to the stage in which synapsis is completed. However, there are no structural or epigenetic differences similar to those found in males in either of the two X chromosomes. Finally, we observed that recombination in the sex chromosomes is restricted in both sexes. In males, crossover-associated MLH1 foci are located exclusively in the distal regions, indicating incipient differentiation of one of the sex chromosomes into a neo-Y. Notably, in female meiosis, the central region of the X chromosome is also devoid of MLH1 foci, revealing a lack of recombination, possibly due to insufficient homology. Overall, these results reveal new clues about the origin and evolution of sex chromosomes.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00755-y
       
  • The Trithorax group protein ASH1 requires a combination of BAH domain and
           AT hooks, but not the SET domain, for mitotic chromatin binding and
           survival

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      Abstract: Abstract The Drosophila Trithorax group (TrxG) protein ASH1 remains associated with mitotic chromatin through mechanisms that are poorly understood. ASH1 dimethylates histone H3 at lysine 36 via its SET domain. Here, we identify domains of the TrxG protein ASH1 that are required for mitotic chromatin attachment in living Drosophila. Quantitative live imaging demonstrates that ASH1 requires AT hooks and the BAH domain but not the SET domain for full chromatin binding in metaphase, and that none of these domains are essential for interphase binding. Genetic experiments show that disruptions of the AT hooks and the BAH domain together, but not deletion of the SET domain alone, are lethal. Transcriptional profiling demonstrates that intact ASH1 AT hooks and the BAH domain are required to maintain expression levels of a specific set of genes, including several involved in cell identity and survival. This study identifies in vivo roles for specific ASH1 domains in mitotic binding, gene regulation, and survival that are distinct from its functions as a histone methyltransferase.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00762-z
       
  • Unravelling HP1 functions: post-transcriptional regulation of stem cell
           fate

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      Abstract: Abstract Heterochromatin protein 1 (HP1) is a non-histone chromosomal protein first identified in Drosophila as a major component of constitutive heterochromatin, required for stable epigenetic gene silencing in many species including humans. Over the years, several studies have highlighted additional roles of HP1 in different cellular processes including telomere maintenance, DNA replication and repair, chromosome segregation and, surprisingly, positive regulation of gene expression. In this review, we briefly summarize past research and recent results supporting the unexpected and emerging role of HP1 in activating gene expression. In particular, we discuss the role of HP1 in post-transcriptional regulation of mRNA processing because it has proved decisive in the control of germline stem cells homeostasis in Drosophila and has certainly added a new dimension to our understanding on HP1 targeting and functions in epigenetic regulation of stem cell behaviour.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00760-1
       
  • BAC- and oligo-FISH mapping reveals chromosome evolution among Vigna
           angularis, V. unguiculata, and Phaseolus vulgaris

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      Abstract: Abstract Cytogenomic resources have accelerated synteny and chromosome evolution studies in plant species, including legumes. Here, we established the first cytogenetic map of V. angularis (Va, subgenus Ceratotropis) and compared this new map with those of V. unguiculata (Vu, subgenus Vigna) and P. vulgaris (Pv) by BAC-FISH and oligopainting approaches. We mapped 19 Vu BACs and 35S rDNA probes to the 11 chromosome pairs of Va, Vu, and Pv. Vigna angularis shared a high degree of macrosynteny with Vu and Pv, with five conserved syntenic chromosomes. Additionally, we developed two oligo probes (Pv2 and Pv3) used to paint Vigna orthologous chromosomes. We confirmed two reciprocal translocations (chromosomes 2 and 3 and 1 and 8) that have occurred after the Vigna and Phaseolus divergence (~9.7 Mya). Besides, two inversions (2 and 4) and one translocation (1 and 5) have occurred after Vigna and Ceratotropis subgenera separation (~3.6 Mya). We also observed distinct oligopainting patterns for chromosomes 2 and 3 of Vigna species. Both Vigna species shared similar major rearrangements compared to Pv: one translocation (2 and 3) and one inversion (chromosome 3). The sequence synteny identified additional inversions and/or intrachromosomal translocations involving pericentromeric regions of both orthologous chromosomes. We propose chromosomes 2 and 3 as hotspots for chromosomal rearrangements and de novo centromere formation within and between Vigna and Phaseolus. Our BAC- and oligo-FISH mapping contributed to physically trace the chromosome evolution of Vigna and Phaseolus and its application in further studies of both genera.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00758-9
       
  • Anatomy and evolution of a DNA replication origin

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      Abstract: Abstract DNA amplification occurs at the DNA puff II/9A locus in the fungus fly Sciara coprophila. As a foundation to study the molecular mechanism for the initiating events of II/9A DNA re-replication, we have sequenced 14 kb spanning a DNase hypersensitive site (DHS) upstream of the 1 kb amplification origin and through transcription units II/9–1 and II/9–2 downstream of the origin. These elements are annotated as well as the ORC binding site at the origin and the transition point (TP) between continuous and discontinuous DNA syntheses that marks the origin of bidirectional replication at the nucleotide level. A 9 bp motif found at the TP is repeated near the other end of the 1 kb ORI and may identify a putative second TP. The steroid hormone ecdysone induces DNA amplification as well as transcription and puffing at locus II/9A. Within the 14 kb, several matches to the ecdysone response element (EcRE) consensus sequence were identified, including some in the amplification origin region. EcRE O-P is at a central axis of a remarkable symmetry, equidistant to the TPs that are themselves equidistant to EcRE O-1 and EcRE O-2. DNA sequence alterations have occurred throughout the II/9A region in a newly discovered polymorphism (#2). Polymorphism #2 is not specific to developmental stage, sex, or tissue, and it does not impair DNA amplification. The DHS, both 9 bp TP sequences, and EcREs O-1, O-P, and O-2 are conserved between the polymorphism #1 and #2 sequences, suggesting their functional importance and retention during evolutionary selection. Moreover, a 72 bp sequence in the Sciara DHS at DNA puff II/9A is conserved in DNA puff C-3 of Rhynchosciara americana. Comparisons are discussed between the Sciara II/9A amplicon and the chorion locus amplicon on the third chromosome of Drosophila.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00756-x
       
  • Chromosomal positioning in spermatogenic cells is influenced by
           chromosomal factors associated with gene activity, bouquet formation and
           meiotic sex chromosome inactivation

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      Abstract: Abstract Chromosome territoriality is not random along the cell cycle and it is mainly governed by intrinsic chromosome factors and gene expression patterns. Conversely, very few studies have explored the factors that determine chromosome territoriality and its influencing factors during meiosis. In this study, we analysed chromosome positioning in murine spermatogenic cells using three-dimensionally fluorescence in situ hybridization-based methodology, which allows the analysis of the entire karyotype. The main objective of the study was to decipher chromosome positioning in a radial axis (all analysed germ-cell nuclei) and longitudinal axis (only spermatozoa) and to identify the chromosomal factors that regulate such an arrangement. Results demonstrated that the radial positioning of chromosomes during spermatogenesis was cell-type specific and influenced by chromosomal factors associated to gene activity. Chromosomes with specific features that enhance transcription (high GC content, high gene density and high numbers of predicted expressed genes) were preferentially observed in the inner part of the nucleus in virtually all cell types. Moreover, the position of the sex chromosomes was influenced by their transcriptional status, from the periphery of the nucleus when its activity was repressed (pachytene) to a more internal position when it is partially activated (spermatid). At pachytene, chromosome positioning was also influenced by chromosome size due to the bouquet formation. Longitudinal chromosome positioning in the sperm nucleus was not random either, suggesting the importance of ordered longitudinal positioning for the release and activation of the paternal genome after fertilisation.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00761-0
       
  • Deletion of the XIST promoter from the human inactive X chromosome
           compromises polycomb heterochromatin maintenance

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      Abstract: Abstract Silencing most gene expression from all but one X chromosome in female mammals provides a means to overcome X-linked gene expression imbalances with males. Central to establishing gene silencing on the inactivated X chromosome are the actions of the long non-coding RNA XIST that triggers the repackaging of the chosen X into facultative heterochromatin. While understanding the mechanisms through which XIST expression is regulated and mediates its affects has been a major focus of research since its discovery, less is known about the role XIST plays in maintaining chromatin at the human inactive X chromosome (Xi). Here, we use genome engineering to delete the promoter of XIST to knockout expression from the Xi in non-cancerous diploid human somatic cells. Although some heterochromatin features exhibit limited change at the Xi, two of those assessed showed significant reductions including histone H2A monoubiquitylation at lysine 119 and histone H3 trimethylation at lysine 27, both of which are covalent histone modifications catalyzed by the polycomb repressive complexes 1 and 2 respectively. Coupled with these reductions, we observed an occasional gain of euchromatin signatures on Xp, but despite these signs of chromatin instability, we did not observe appreciable changes in the reactivation of genes from the Xi. Collectively, these data are consistent with maintenance of dosage compensation at the Xi involving multiple redundant layers of gene silencing.
      PubDate: 2021-09-01
      DOI: 10.1007/s00412-021-00754-z
       
 
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