Cytogenetic and Genome Research最新文献

Background: Robertsonian (Rb) chromosomal rearrangements are very common in mammals and are the primary basis of chromosome number variation between species. The fertility of heterozygotes has particular significance in understanding the mode of fixation of Rb rearrangements, and could have a role in the attainment of reproductive isolation by chromosomally differentiated species. Summary: Here we survey available data on fertility of Rb heterozygotes in mammals, comparing with homozygotes, and considering effects on litter size, frequencies of anaphase I nondisjunction, germ cell death and pachytene features associated with that germ cell death. We consider both simple heterozygotes which form trivalent configurations at meiosis I and complex heterozygotes which form longer configurations due to heterozygosity for different chromosomes with monobrachial homology. Two species have a particularly wide variety of Rb heterozygotes and have been well studied: the house mouse (the western subspecies) and the common shrew. The overall data confirm that heterozygosity for a single Rb metacentric may be associated with near-normal fertility in mammals, though not in every instance. Usually infertility is not going to be a substantial hindrance to fixation of Rb fusions or fissions. Nor is infertility in simple heterozygotes for one or a few Rb metacentrics on its own likely to promote reproductive isolation. However, simple heterozygotes forming many meiotic trivalents and complex heterozygotes forming long meiotic configurations may suffer substantial infertility or sterility. Even so, heterozygous house mice and common shrews forming the very longest meiotic chains and rings may produce some young. We discuss the implications of these findings with regards the role of Rb rearrangements in speciation. Key Messages: Infertility due to Rb heterozygosity on its own may rarely hinder fixation of Rb rearrangements nor be sufficient to cause a complete interruption to gene flow between hybridizing chromosomal forms. However, this does not rule out a role for Rb rearrangements in speciation. Reinforcement is possible, and Rb rearrangements have the potential to act in synergy with genic incompatibilities to promote reproductive isolation. There can also be the contrary process of despeciation. Natural selection may respond in various ways to a given degree of infertility.

Introduction: Telomeric sequences are stable parts of the genome and are widely conserved among higher level taxa (e.g., TTAGG in insects and other arthropods) although exceptions are known and their numbers are increasing with research. The true bug suborder Heteroptera (Hemiptera) includes more than 40,000 species in about 100 families, classified into seven infraorders. Four different telomeric motifs are currently known in Heteroptera, including (TTAGG)_n, (TTAGGGATGG)_n, (TTAGGGGTGG)_n, and (TTAGGGTGGT)_n. The canonical "insect" motif (TTAGG)_n was found in representatives of two infraorders, Nepomorpha and Cimicomorpha. Derived motifs were found in a few species previously known as TTAGG-negative in the evolutionarily advanced sister infraorders Cimicomorpha and Pentatomomorpha (= Terheteroptera). Here, we studied telomeric motifs in 20 species of true bugs belonging to 10 families of Terheteroptera.

Methods: We used fluorescence in situ hybridization with the "insect" telomeric probe (TTAGG)_n and an alternative probe (TTAGGGATGG)_n to map the distribution of telomeric sequences in the chromosomes of 8 species of Pentatomomorpha (from the families Pentatomidae, Rhopalidae, Lygaeidae, Geocoridae, and Blissidae). We also analyzed chromosome-level genome assemblies available in the NCBI database for another 4 species of Pentatomomorpha (from Alydidae, Coreidae, and Pentatomidae) and 8 species of Cimicomorpha (from Reduviidae, Miridae, and Anthocoridae).

Results: Overall, we identified telomeric sequences in all but one (Geocoris dispar; Geocoridae) species. The telomeric motif (TTAGGGATGG)_n was detected in both Cimicomorpha (in the families Anthocoridae and Miridae) and Pentatomomorpha (in Blissidae, Lygaeidae, Pentatomidae, and Rhopalidae); the motif (TTAGGGGTGG)_n was found only in Pentatomomorpha (in Alydidae, Coreidae, and Pentatomidae); and the canonical "insect" motif (TTAGG)_n was found in the family Reduviidae (Cimicomorpha). With our new data, telomeric motifs are now known for 40 species of true bugs from 30 genera, 13 families and 3 infraorders, including Nepomorpha, Cimicomorpha, and Pentatomomorpha. Noncanonical motifs are found so far only in the Terheteroptera clade and are dominant in this group, with (TTAGGGATGG)_n leading.

Conclusion: Our new data have expanded the understanding of telomere composition and evolution in Cimicomorpha and Pentatomomorpha and suggested that (TTAGGGATGG)_n telomeric sequences can be considered ancestral for the entire clade Terheteroptera.

Introduction: Spindles are microtubules-based machines whose primary function is to accurately segregate chromosomes in both mitotic and meiotic cell division. The structure of spindles is critical for their function; errors in morphology or attachment to chromosomes lead to aneuploidy, potentially resulting in disease, infertility, and lethality. Electron microscopy studies have yielded fine-detail spindle ultrastructures in many plant and animal species, but no studies have investigated the spindle of Zea mays, a critical crop, and cytogenetic model system.

Methods: Here we use electron tomography (ET), reconstruction, and modeling to obtain three-dimensional, nanometer-resolution of the Z. mays meiotic spindle. Structures such as microtubules, kinetochores, vesicles, membrane channels, and nuclear envelope were modeled through a partial spindle reconstruction, and confirmed using immunostaining and live fluorescence microscopy.

Results: ET revealed that maize spindles contain 8-18 kinetochore microtubules (kMTs) per kinetochore, which are approximately 776 nm in diameter and 316 nm in depth. Small ∼37 nm vesicles were identified, as well as larger (∼5 µm long, 800 nm wide) membrane structures with channels that allow spindle microtubules to pass through. These membrane channels stain positively for the ER-marker protein disulfide isomerase. Imaging of prophase meiotic cells revealed a cross-hatch microtubule arrangement in the perinuclear ring on the external surface of the nuclear envelope, which also contained type II nuclear grooves with transnuclear microtubules passing from the nucleus to the cytoplasm.

Conclusions: Z. mays meiotic spindles are similar to animal counterparts with a comparable number of kMTs and pre-spindle transnuclear microtubules but also plant-specific features such as Golgi-derived vesicles to assist cell plate formation, internal ER membrane channels, and a perinuclear microtubule ring that aids spindle assembly. Maize kinetochores have an electron-diffuse ball in cup morphology that is comparable in size to Drosophila kinetochores and larger than mammalian kinetochores.

Introduction: The mapping of the satellite DNA on chromosomes is vital to understanding the distribution and evolution of repetitions in the genome since these chromosomal studies have shown the origin, evolutionary mode, and function of repetitive sequences. This study aimed to prospect the satellitome and determine its location in the genome of two cryptic species of Hypostomus, H. aff. ancistroides and H. ancistroides, with and without XX/XY sexual chromosome system.

Methods: Mitotic chromosomes and DNA extraction were obtained according to protocols. After the whole genome sequencing, the satDNAs were retrieved, amplified, and hybridized in chromosome preparations for male and female individuals.

Results: We found 30 satellite families (47 variants, two superfamilies) in H. ancistroides and 38 satellite families (45 variants, four superfamilies) in H. aff. ancistroides. The sequences varied from 14 bp to 2,662 bp in H. ancistroides and from 14 bp to 2,918 bp in H. aff. ancistroides. We did not observe any tandem repeats that were exclusive to each of the libraries; however, many sequences showed very different abundances and copy numbers between the libraries. Four satDNAs did not hybridize on the chromosomes of either species. Conversely, one satDNA hybridized in both species, HxySat1-80. However, the phenotypes found varied among species, populations, and in the same individual. There was no sign of HanSat3-464 and HanSat11-335 in any individuals of H. aff. ancistroides, but markings were in the chromosomes of H. ancistroides. HxySat12-1127 and HxySat8-52, on the other hand, were only hybridized in H. aff. ancistroides, while H. ancistroides had a negative sign. No hybridization of satDNAs was found in the X and Y sex chromosomes as they were mostly composed of euchromatin.

Conclusion: We distinguish H. aff. ancistroides as genetically different from H. ancistroides, recognizing that such characteristics go far beyond morphological, karyotypic, and molecular data. Our data support the differential abundance and location of satellite DNAs and confirm that many organisms, including fish, have repetitive sequences that validate the library hypothesis. All found and validated satDNAs and the characterization of the satellitomes of the two species represent important contributions to cytogenomic studies of the genus Hypostomus.

Introduction: Sex chromosomes have evolved independently across various lineages, often showing convergent degradation of the sex-limited chromosome. While extensively studied in model organisms with ancient sex chromosomal systems, the evolution of early-stage sex chromosomes remains poorly understood. Eulimnadia texana, a freshwater crustacean with a unique androdioecious breeding system (ZZ, ZW, and viable WW genotypes), provides a rare opportunity to study early sex chromosome evolution. This study examines E. texana's W chromosome for evidence of a small localized non-recombining region, characterized by a transposable element (TE) "hotspot," low gene density, and low GC content.

Methods: Sex-linked markers were mapped onto the W chromosome (scaffold 1). TEs in the WW genome were identified using RepeatModeler and RepeatMasker. Statistical analyses compared TE distribution between the genome and scaffold 1, which was then divided into 20 equal-sized "bins" for finer-scale statistical analyses. Gene density and GC content were analyzed across these bins.

Results: While no significant TE accumulation was found across the entire W chromosome compared to the remaining genome, a specific region (6.6-8.8 Mb, fourth bin) showed significantly higher TE accumulation. This region also exhibited low gene density and low GC content, indicative of reduced recombination.

Conclusion: Our findings suggest that E. texana's W chromosome contains a smaller region of crossover suppression, supporting the hypothesis that it is a proto-sex chromosome in early evolutionary development. This study provides valuable insights into early sex chromosome evolution and establishes E. texana as an ideal model for further investigation of evolutionary processes driving proto-sex chromosome differentiation.

Background: Various malignancies can be efficiently combated by focusing on glutathione. It is unclear how glutathione-related genes link to diffuse large B-cell lymphoma (DLBCL).

Methods: Clinical information was gathered from DLBCL patients, and differences in glutathione-related differentially expressed genes (DEGs) between DLBCL and healthy groups were found. Enrichment analysis was run on the DEGs associated with glutathione. We discovered hub genes in glutathione, confirmed hub genes' capacity for diagnosis and function prediction, and estimated drug sensitivity. Immune microenvironmental variations between healthy and DLBCL people were assessed, and hub genes for transcription factor (TF) targeting and miRNAs were found.

Results: The glutathione-related DEGs were linked to biological processes such as response to oxidative stress and response to xenobiotic stimulus, according to enrichment analysis. Out of DEGs associated with glutathione, six hub genes were chosen. In the DLBCL population, there was a notable upregulation of the six hub genes. All the genes' AUC values in the diagnostic ability category were more than 0.7, showing strong hub gene diagnostic capacity. The DLBCL population had a high level of T-cell infiltration, according to immune infiltration analysis techniques. Similar activities, such as the cell cycle G2/M phase transition and the negative control of organelle formation, are demonstrated by gene function prediction for hub. According to drug sensitivity prediction, there was a favorable link between KPNA2 with pracinostat, BRCA1 with B-7100, and LEE-011. The gene KPNA2 was shown to be concurrently targeted by many miRNAs and TFs, according to the miRNA-gene-TF interaction network.

Conclusion: The relationship between DLBCL and glutathione-related genes was uncovered by our research, and six glutathione genes were linked to DLBCL. These genes might be used as diagnostic biomarkers or targets for treatment for DLBCL patients.

Background: Our study focuses on Yakutian cattle, a Siberian native breed, examining its inbreeding and diversity through genome-wide analysis of runs of homozygosity (ROHs). Yakutian cattle are adapted to Siberia's harsh sub-arctic conditions, enduring temperatures below -70°C. However, the population genetics studies on this breed are scanty, to document the genetic uniqueness in these cattle.

Results: We analyzed 40 Yakutian cattle with strict quality control for ROH detection yielding 683 homozygous segments, averaging 17 per individual with an average length of 9 Mb. ROH regions were found to be involved in important pathways pertaining to cold adaptation. Autozygosity ranged from 1% to 12% of the genome, with a relatively low average inbreeding coefficient (FROH) of 0.057, as compared to other breeds. Also, the different diversity indicators, namely, principal component analysis, heterozygosity, and effective population size analysis, revealed the prevalence of genetic diversity within the breed.

Conclusion: Our findings on ROH are the first of its kind in Yakutian cattle that support their adaptability to colder environments, as evidenced by low inbreeding and high genetic diversity.

Introduction: The dual diagnosis of Down syndrome and Turner syndrome in the same patient was clinically identified in the early 1950s before the development of karyotyping techniques. After that, several authors reported anecdotal patients and/or reviewed series of Down-Turner double aneuploidies due to a regular 46,X,+21 constitution or different combinations of abnormal cell lines. In such cases, the most typical presentation encompasses the female sex, Down syndrome phenotype, and chromosomal mosaicism.

Case presentation: Here we report a female patient presenting with short stature, dysmorphic features, developmental delay, and learning disabilities, whose karyotype revealed a previously undescribed 45,X[47]/48,XXX,+21[3] constitution.

Conclusion: This is the first case encompassing these three aneuploidies together and, contrary to most previous reports, exhibiting a predominantly Turner syndrome phenotype associated with developmental delay.

Background: Aurora kinase B (Aurora-B), a member of the chromosomal passenger complex, is involved in correcting kinetochore-microtubule (KT-MT) attachment errors and regulating sister chromatid condensation and cytoplasmic division during mitosis.

Summary: However, few reviews have discussed its mechanism in oocyte meiosis and the differences between its role in mitosis and meiosis. Therefore, in this review, we summarize the localization, recruitment, activation, and functions of Aurora-B in mitosis and oocyte meiosis. The accurate regulation of Aurora-B is essential for ensuring accurate chromosomal segregation and correct KT-MT attachments. Aurora-B regulates the stability of KT-MT attachments by competing with cyclin-dependent kinase 1 to control the phosphorylation of the SILK and RVSF motifs on kinetochore scaffold 1 and by competing with protein phosphatase 1 to influence the phosphorylation of NDC80 which is the substrate of Aurora-B. In addition, Aurora-B regulates the spindle assembly checkpoint by promoting the recruitment and activation of mitotic arrest deficient 2.

Key messages: This review provides a theoretical foundation for elucidating the mechanism of cell division and understanding oocyte chromosomal aneuploidy.