Cytogenetic and Genome Research最新文献

Introduction: Thamnophilidae (typical antbirds) are a diverse family of insectivorous passerine birds restricted to neotropical forests, encompassing 237 species, of which only five have been studied cytogenetically.

Methods: To investigate the chromosomal evolution of this group, we applied classical and molecular cytogenetic techniques, including conventional staining, C-banding, and fluorescence in situ hybridization (FISH) with probes for repetitive telomeric sequences (TTAGGG)5 and 18S rDNA, in two representative species: Thamnophilus caerulescens and Thamnophilus ruficapillus.

Results: The karyotypes of T. caerulescens and T. ruficapillus comprise 80 and 82 chromosomes, respectively. In addition to a possible fission in T. ruficapillus, morphological differences suggest the occurrence of pericentric inversions in the chromosomes of this species. The patterns of constitutive heterochromatin differed between the species: both showed centromeric markings and heterochromatin on the W chromosome, but T. ruficapillus also exhibited interstitial markings on seven chromosomal pairs. Both species presented interstitial telomeric sequences (ITSs) in the first seven pairs, which corresponded to constitutive heterochromatin in T. ruficapillus. The 18S rDNA probe hybridized to a single pair of microchromosomes in T. caerulescens and two pairs in T. ruficapillus.

Conclusion: This study revealed novel patterns of constitutive heterochromatin in T. ruficapillus and ITSs in both species, which have not been previously observed in Passeriformes. The correspondence between constitutive heterochromatin and ITSs in T. ruficapillus suggests that these sequences are composed of repetitive DNA highly similar to telomeric sequences and/or are remnants of pericentric inversions, whereas in T. caerulescens, other mechanisms seem to be involved. The differences in observed patterns highlight distinct chromosomal evolution between these species, emphasizing the diversity within the family Thamnophilidae and the genus Thamnophilus, in contrast to the conserved patterns typically observed in the class Aves.

Introduction: Türkiye houses rich freshwater ichthyofauna with many endemic species. This diversity, however, poses taxonomic challenges and leads to ongoing re-evaluations of various fish genera and species. Here, we sought to analyse the karyotype and other chromosomal characteristics of the newly erected monotypic genus Turcichondrostoma to produce and validate cytogenetic markers potentially informative for future comparative studies.

Methods: We examined an endemic species Turcichondrostoma fahirae (Tefenni nase) using conventional karyotyping and chromosome banding procedures (C-, fluorescent, and silver-nitrate banding/staining), as well as chromosomal mapping of 5S/18S ribosomal DNA (rDNA), U1/U2 small nuclear DNA (snDNA), and telomeric repeats.

Results: A diploid chromosome number (2n) of T. fahirae was 50, consistent with conservative leuciscid pattern. The karyotype was composed of 12 metacentric, 22 submetacentric, 10 subtelocentric and 6 acrocentric chromosomes. Low amount of constitutive heterochromatin was distributed almost exclusively across the pericentromeric regions of all chromosomes, with the most prominent C-bands being placed on a single chromosome pair carrying nucleolar organizer region (NOR). NORs (visualized consistently by silver-nitrate staining, Chromomycin A3 and fluorescence in situ hybridization - FISH) exhibited marked size heteromorphism and were adjacent to a more centromere-proximal 5S rDNA site on the long arm. Additional 5S rDNA clusters occupied short arms of four acrocentric chromosomes, and another single subtelocentric pair carried a single co-localized U1/U2 snDNA site. No interstitial telomeric sequences were detected.

Conclusion: We performed a pioneer molecular cytogenetic study in Turkish freshwater fish species and our data suggest that molecular cytogenetic markers will aid in future taxonomic comparisons. Our findings further corroborate conserved karyotype structure of leuciscid fishes in general.

Introduction: Here we compare differences in the presence of telomeric signals (tDNA-FISH) among karyotypes of taxa having different whole-arm chromosomal rearrangements under the assumption of their participation in differentiation/integration processes during karyotype evolution. We analyzed cytogenetic peculiarities of Robertsonian-like (centromeric) and tandem (telomere-involving) rearrangements using examples of the authors' recent research on comparative cytogenetics of mammals. New data on intra- and interspecific karyotype variation helped to understand the nature of chromosomal rearrangements and their molecular features within and between species in two mammalian taxa: representatives of two genera from two orders (insectivores and rodents).

Methods: To detect telomeric repeats in karyotypes of representatives of the Eurasian genus Sorex and Ethiopian endemic Stenocephalemys, G-banded metaphase chromosomes were hybridized in situ with a fluorescein-conjugated peptide nucleic acid probe and 5-TAMRA-labeled (CCCTAA)4 oligonucleotides.

Results: We compared the location of a molecular chromosomal trait-telomeric sequences-among karyotypes of taxonomically distinct individuals having different types of whole-arm chromosomal rearrangements. Along with the regular terminal location of the telomeric signal on all chromosomes, displays of interstitial telomeric sequences (ITSs) were detectable. This pattern was typical for a studied shrew specimen whose karyotype corresponded to a natural interracial F1 hybrid. This finding doubles the number (known to date) of S. araneus race-specific metacentrics having an identified telomeric signal. In karyotypes of Stenocephalemys specimens, we revealed individual differences in autosomes corresponding to tandem fusion rearrangements, possibly species-specific, for the first time. No intrachromosomal telomeric signal expected in this case was detectable in autosomes, whereas we registered ITSs in pericentromeric regions on X chromosomes near a short, completely heterochromatic (additional) arm.

Conclusion: The new data indicates a heterogeneous distribution of the telomeric signal (tDNA-FISH) on mitotic chromosomes that are involved in (typical for mammals) whole-arm chromosomal variation, thus representing two models of karyotype evolution: Robertsonian polymorphism and tandem fusions. In the analyzed examples of whole-arm chromosomal rearrangements, displays of the centromeric ITS signal more likely represent an integral feature of cytogenetic relatedness within a species (chromosomal races) or between species (in a genus or group of genera) than differentiation of taxa.

The International Standing Committee on Human Cytogenomic Nomenclature (ISCN SC) considered feedback from the cytogenomics community to provide a more user friendly and organised presentation of general rules, improved example descriptions, more representative examples and additional abbreviations. The ISCN 2024 edition represents one of the most significant reviews. Nomenclature for describing the findings of genomic mapping has been included for the first time. A key achievement of the Committee in preparing the ISCN 2024 is the provision of standardised nomenclature to ensure consistency in the ISCN description of findings irrespective of the cytogenomic technology used. This report highlights the main changes in the ISCN 2024 compared to previous editions and is a guide to assist in the transition to its implementation as the current nomenclature for describing cytogenomic findings.

Introduction: DNA damage may affect homeostasis on spermatogonial stem cells(SSCs), while the details relationship with male infertility still remains unclear. Therefore, it is important that further research into the mechanisms related to DNA damage and genomic stability on spermatogonial stem cells.

Methods: scRNA-seq datasets from Idiopathic non-obstructive azoospermia (NOA) and normal testes were collected and testicular cells were further annotated via UMAP. Based annotation on the sequencing data, WGCNA analysis on the deferentially expressed genes was conducted , LASSO regression and the MNC calculation algorithm in Cytoscape were carried out to find genes associated with DNA damage repair.

Results: It was found that SSCs were mainly concentrated in normal samples, and the differences in subcluster pathways reflected the heterogeneity of NOA. While the characteristics of the interaction between Leydig cells and other cells were clarified, and the importance of the PTN signaling pathway in SSCs development was discovered, which participates in SSCs development through SDC2. Combining the marker genes of SSCs and DNA damage-related genes in single-cell analysis, a PPI network was constructed. Through LASSO regression and the MNC calculation algorithm in Cytoscape, ATRX, DOT1L, and RUVBL2 were finally identified as key diagnostic genes.

Conclusion: Our results revealed predictable mechanisms of testicular micro-environment and DNA damage in the regulation of human SSCs and propose potential therapeutic targets for male infertility. Subsequently, further research to confirm the predicted potential mechanisms, pathways, and therapeutic targets should be conducted.

Background: Tandemly repeated satellite DNA sequences are an important part of animal genomes. They are involved in chromosome interactions and the maintenance of the integral structure of the nucleus, regulation of chromatin conformation and gene expression, and chromosome condensation and movement during cell division. Satellite DNAs located in the centromeric heterochromatin evolve rapidly and likely affect hybrid fertility and fitness. However, their studies are taxonomically highly biased. In lacertid lizards, satDNA has been extensively studied in the subfamily Lacertinae, but the subfamily Eremiadinae has been largely overlooked.

Results: In this work, we describe a novel 177-bp-long centromeric satDNA family EremSat177, which is present in all studied species of the genus Eremias, but not in related genera. EremSat177 is not homologous to any previously identified centromeric satellites. Using fluorescence in situ hybridization, we demonstrate its centromeric localization in E. velox and E. arguta. We also show its tandem organization and intra-genomic homogenization by in silico analysis in the genome of E. argus. The phylogenetic analysis of consensus EremSat177 sequences from 12 Eremias species demonstrates that the same monomer subfamily is the most abundant in all these species, and its evolution mainly follows the species phylogeny as revealed by the mtDNA sequences.

Conclusion: The EremSat177 represents a novel, lineage-specific centromeric satellite DNA, and its role in centromere functioning should be revealed in further research.

Introduction: Satellite DNA is an important component of the eukaryotic genome. Some satellite DNAs plays an important role in various biological processes. The red-eared slider (Trachemys scripta elegans, 2n=50, C=1.43 pg) belongs to the American freshwater turtle family and is recognised as one of the world's most invasive species. In the T. s. elegans chromosome-level genome assembly, which has been recently published, satellite DNAs comprise only 0.1%. From the repetitive repertoire of the T. elegans genome, only ribosomal DNA genes and telomeric repeats have been localised on the species' chromosomes.

Methods: Using publicly available short-read sequencing data, we conducted de novo identification of the most abundant satellite DNAs in T. s. elegans using TAREAN pipeline. We combined bioinformatics (using blastn) and chromosome mapping by fluorescence in situ hybridization to describe the distribution of major tandem repetitive DNAs. The diversity and distribution of satDNA in the assembled genome of T. s. elegans were explored using the SatXplor pipeline.

Results: Six major satellite sequences occupying approximately 0.8% of the genome were identified in the genome data, all of which were successfully localised both in situ and in silico on T. s. elegans chromosomes and in silico on chromosomal scaffolds. We revealed a complex structural organisation of these sequences: monomers may be moderately or highly variable and they may contain regions homologous to retrotransposons. Cytogenetic mapping showed the accumulation of satellite DNAs in the pericentromeric regions of most chromosomes and in the distal regions of the short arms of submetacentric chromosomes. Comparisons between cytogenetic maps and genome assembly data revealed discrepancies in the number and chromosomal locations of the identified satellite DNA clusters.

Conclusion: The red-eared slider genome has a greater proportion of satellite DNA than was previously reported. These satellites demonstrate no specificity for either macrochromosomes or microchromosomes. Differences between in situ and in silico results indicate the challenges of repetitive sequence assembly, as well as discrepancies between chromosome numbering in the current chromosome-level genome assembly and the physical chromosome map.

Introduction: DNA helicases are vital for preserving genome integrity and ensuring the correct process of meiosis. Despite their recognized significance, the precise roles and spatial dynamics of these enzymes during meiotic prophase I remain largely unexplored.

Methods: The key methodology of this study consisted of immunocytochemical staining and statistical evaluation.

Results: Our results demonstrate that RTEL1 is present in regions that have just initiated synapsis, emphasizing that chromosome synapsis is not only essential for this helicase but potentially for other proteins involved in meiotic processes. Since RTEL1 and replication protein A (RPA) were previously shown to colocalize in somatic cells, we sought to assess this relationship in meiosis. During early pachytene, when RTEL1 and RPA levels are at their peak, several immunofoci of these proteins exhibited complete or partial overlap, suggesting colocalization in some chromosomal regions, though some remained distinct. The earlier appearance of RPA in meiotic nuclei supports the notion that it may facilitate RTEL1 recruitment for DNA repair. As meiosis progresses from early pachytene to diplotene, the significant decrease in RTEL1 and RPA signals underscores their predominant involvement in early prophase I.

Conclusion: This study identifies RTEL1 as the third helicase, following BLM and FANCJ, to be detected in prophase I, suggesting that additional helicases may be added to this list in the future. Its unique synapsis-dependent behavior distinguishes it from the other two helicases, which do not exhibit such a pattern. Furthermore, our findings suggest that RTEL1 can demonstrates antirecombinase activity and functions as part of the meiotic helicase complex, which regulates critical aspects of meiotic processes.

Introduction: The Phasianidae family belongs to Galliformes, which is basal to other Neognathae. Despite the availability of chromosome-level genome assemblies for many Phasianidae species, the karyotypes for some species remain poorly investigated.

Methods: In this study, we described karyotypes using classical, differential, and molecular cytogenetic (BAC-FISH) methods. To compare chromosome-level genomes of 10 Galliformes species dot-plot analysis was performed.

Results: We provide the first comprehensive description of the karyotype of two Tetraonini species: the western capercaillie (Tetrao urogallus, 2n=78) and the hazel grouse (Tetrastes bonasia, 2n=80). We mapped chicken BAC clones (CHORI-261) with known coordinates to the chromosomes of the western capercaillie and Japanese quail (Coturnix japonica, 2n=78) to anchor physical chromosomes to chromosome-level assemblies. Finally, we performed dot-plot comparisons of ten available chromosome-level genome assemblies to identify inter- and intrachromosomal rearrangements in Galliformes.

Conclusion: We show that the centromeric fusion of orthologs of GGA6 and GGA8 is shared by all analyzed species in the tetraonid clade: T. urogallus, T. bonasia, and Lagopus muta. We identified linage-specific intrachromosomal rearrangements on chromosomes orthologs to chicken Z (Phasianinae and Tetraoninae), 7 and 12 (Phasianinae and Tetraoninae), 5 and 13 (Perdicinae), 22 (Alectoris). Our study shows that analysis of the genomes of several closely related species allows us to identify chromosomal rearrangements characteristic of individual evolutionary lines.