Microchromosomes Research Articles

Expression and clinical significance of microchromosome maintenance protein 10 in thalamic gliomas

Objective To investigate the expression of microchromosome maintenance protein 10(MCM10) in thalamic gliomas and its prognostic value. Methods A retrospective analysis was conducted on the clinical data of 48 patients with thalamic glioma who underwent tumor resection at Neurosurgery Department of Beijing Tiantan Hospital, Capital Medical University from September 2016 to September 2017. At 1 week post operation, the degree of tumor resection was determined according to cranial MRI. After discharge, all patients underwent follow-up by outpatient clinic visits or telephone, which included reexamination of skull enhanced MRI and assessment of Karnofsky performance scale(KPS) score. All tumor tissues were reserved during operation for immunohistochemical staining analysis of MCM10. According to the positive rate of MCM10 expression and comprehensive score of staining intensity, the lower expression of MCM10 was decided as less than 6 points, and the higher expression of MCM10 as at least 6 points. The expression of MCM10 in different grade thalamic gliomas was analyzed. We then compared the clinical data of MCM10 low expression group and high expression group. The survival of two groups was further analyzed using Kaplan-Meier method. Finally, the univariate and multivariate Cox regression analysis methods were used to determine whether MCM10 was an independent risk factor affecting the total survival of thalamic glioma patients. Results In 48 patients, 1 week after surgery, the cranial MRI showed that total resection was achieved in 13 cases (27.1%), near-total resection in 29 cases (60.4%) and partial resection in 6 cases (12.5%). The median follow-up time was 22.6 months (0.3-34.2 months) in 48 patients. Three months after surgery, the median KPS score was 60 points(0-100 points). By the end of the follow-up period, 31 of the 48 patients survived and 17 died. The results of immunohistochemistry showed that the tumor tissue in 48 patients expressed MCM10, of which 23 (47.9%) were low expression and 25 (52.1%) were high expression. Immunohistochemistry analysis in the 48 patients of thalamic gliomas with various World Health Organization (WHO) grades showed that MCM10 had the lowest staining points (3.7±1.2) in grade Ⅰ glioma, middle-level in grade Ⅱ (5.8±2.3) and grade Ⅲ(7.5±3.5), and the highest in grade Ⅳ (7.9±2.8). The difference between groups was statistically significant (P=0.021). The differences in age, sex, WHO grade, preoperative KPS score and postoperative recurrence of MCM10 high expression group and low expression group were not statistically significant (all P>0.05). The survival rate and KPS score improvement were significantly higher in the patients of MCM10 low expression group than those in the high expression group (both P<0.05). The results of univariate and multivariate Cox regression analysis showed that MCM10 high expression was one of the independent risk factors affecting the outcome of patients with thalamic glioma (HR=0.129, 95% CI: 0.024-0.685, P=0.016). Conclusions MCM10 is expressed in thalamic glioma with the lowest level in WHO Ⅰ grade tumor and the highest in grade Ⅳ. Longer survival is associated with low expression of MCM10, which can be used as an indicator of the prognosis judgment of thalamic glioma. Key words: Thalamus; Glioma; Prognosis; Microchromosome maintenance protein 10

DNA amount of chicken chromosomes resolved by image cytometry

AbstractAvian karyotypes are remarkably conserved throughout evolution. Hence, studies have given priority to the chicken for characterizing and understanding the chromosome organization in this clade. Chicken chromosomes are conventionally classified as macrochromosomes (MACs), microchromosomes (MICs) and sexual chromosomes (ZW). For expanding karyotype data, the DNA amount of the MACs, ZW and a few MICs have been reported. In spite of the progress, hitherto chicken chromosomes have not been fully classified and characterized, especially MICs, accounting for a gap in evolutionary approaches and genomic projects. The chicken karyotype is considered one of the most challenging for cytogenetic study. This study focused on image cytometry, a quantitative measure of the chromosome DNA amount, to fine-tune morphometric data. The methodology was fundamental to identify and discriminate each MIC, overlapping between MICs and MICs/MACs. Associating these data to classical cytogenetic rules, karyograms were assemb...

Comparative cytogenetics of two species of ground skinks: Scincella assata and S. cherriei (Squamata: Scincidae: Lygosominae) from Chiapas, Mexico

Standard karyotypes of two species of the genus Scincella , S. assata and S. cherriei , both from Chiapas State, Mexico, were described for the first time. The diploid chromosome number was 28 in S. assata , whereas 30 in S. cherriei . The karyotypes of the two species, while differing in the number of microchromosomes, 14-15 in S. assata and 16-17 in S. cherriei, share four pairs of large metacentric, two pairs of medium-sized metacentric, and one particular pair (number 7) of chromosomes. Female S. assata carries chromosome pair 7 composed of two identical medium-sized subtelocentric chromosomes. This chromosome pair is heteromorphic in males of both species, i.e., one component of the pair is similar to the homomorphic chromosomes 7 of the S. assata female, while the other is nearly one-half the size of its counterpart and resembles a microchromosome. The homology of such externally different elements is deducted from the presence of an asymmetric bivalent in spermatocytes at diplotene-diakinesis. Female S. cherriei was not available. We suspect that the two Scincella species possess an XY sex determination system, as previously reported for the North American congeneric species, S. lateralis .

Standard karyotype and nucleolus organizer regionof Neotropical blindsnake Typhlops brongersmianus, Serpentes : Typhlopidae

The karyotype of Typhlops brongersmianus is reported on the basis of specimens from north-eastern Argentina. The conventional Giemsa staining showed that the species has 2n = 34 chromosomes, including 8 pairs of macrochromosomes and 9 pairs of microchromosomes. Ag-NOR staining revealed the NORs location on a pair of macrochromosomes. The chromosome number and karyotypic morphology are similar to those of Neotropical typhlopid previously karyotyped.

Karyotype and Banding Patterns of Chicken Breeds

3 Abstract: Traditional karyotyping is invented in animal research for several decades depend on the analysis of characteristic banding patterns along the length of chromosome. In the present study chicken metaphase chromosomes were obtained by peripheral blood lymphocyte culture techniques, G-band patterns were obtained with trypsin and Giemsa, C-band patterns were treated with barium and the nuclear organizer regions (NORs) were identified by silver staining. All species studied presented a diploid number of 7 8 chromosomes, with 10 pairs of macro chromosomes including the sex chromosome and 29 pairs of micro chromosomes. G-band patterns were found quite different between breeds. The dark stained of C-band was observed on micro chromosome and W chromosome. Karyotype resemblance near coefficient was possible for breeds clustering. The position of centromers, relative length, arm ratio and the evolutionary distance of chicken breeds was estimated. The application of chromosome karyotype and banding techniques was used to study the origin, evolution and relationship of species, also used for gene location and sex determination. While, in the Medical field was used to identify genetic disease. The techniques was consider as a base for further molecular research, for example FISH

Effects of higher-order nuclear structure and Rad51 overexpression on radiation-induced chromosome rearrangements

The microchromosomes (MICs) in chicken DT40 lymphocytes are usually clustered in the center of the nucleus, whereas the macrochromosomes (MACs) are preferentially located toward the nuclear periphery. This compartmentalized architecture of the nucleus is associated with a low frequency of translocations between MICs and MACs after induction of DNA breaks by a radiation track(s). In contrast, the MICs in chick embryo fibroblasts (CEFs) tend to be located throughout the entire nuclear volume. The resulting side-to-side arrangement of MIC and MAC territories favors radiation-induced MIC/MAC translocations, which occur more frequently in CEF cells than MIC/MIC or MAC/MAC rearrangements. Collectively, our results suggest that preformed physical contacts are a prerequisite for the generation of chromosome rearrangements through recombinational repair of DNA damage. Cell type-specific higher-order nuclear organization may prevent or stimulate the formation of particular chromosome aberrations in pathology and evolution. Ectopic expression of the recombination protein Rad51 can protect cells from radiation-induced translocations. The repair activity of overexpressed Rad51 is more important for cells that are irradiated in S/G₂ phase than for cells in G₁ phase. Evidently, homologous recombination between sister chromatids of a replicated chromosome is more frequent than that between homologous or heterologous chromosomes during G₁ phase.

Lampbrush chromosomes in the japanese quail Coturnix coturnix japonica: cytological maps of macro chromosomes and meiotic crossover frequency in females

Cytological maps of lampbrush macrobivalents of the Japanese quail (Coturnix coturnix japonica) were constructed. Investigation of chiasmata allowed determination of the meiotic frequency of reciprocal genetic recombination (crossing over) in Japanese quail females. The total chiasma number in bivalents of Japanese quail oocyte nuclei was determined to be 53-58. Macrobivalents 1-5 and Z of the Japanese quail had on average 3.3 chiasmata per bivalent, and microbivalents, 1.0-1.1 chiasmata per bivalent. The chiasmata (crossover) frequency in Japanese quail females was lower than in chicks. In macrochromosomes of Japanese quail females, one crossover occurred per 43.9 Mb, and in chicken, per 30.0 Mb. Judging from chiasma frequency, the genetic length of the Japanese quail genome is likely to be 2650-2900 cM. Crossover frequency in the species was 0.023 per Mb in macrobivalents and 0.07-0.08 Mb in microbivalents and for the total genome, 0.041 crossovers per Mb. The genetic length of one Mb (theta) in female Japanese quails was 1.14 cM in macrochromosomes, 3.60-4.12 cM in microchromosomes, and about 1.96-2.15 cM averaged over the genome.

Chicken microchromosomes are hypermethylated and can be identified by specific painting probes

Microdissection of single chicken microchromosomes (MICs) followed by degenerate oligonucleotide-primed (DOP) PCR allows the rapid generation of MIC-specific DNA libraries. Since some libraries derived from a single (or a few) chromosome(s) label the entire MIC fraction, the majority of chicken MICs share repetitive DNA sequences that are not found on the macrochromosomes. In evolutionarily distant bird species, MICs are invariably hypermethylated. Methylcytosine staining provides additional in situ evidence for the high gene content of MICs and strong compartmentalization of avian genomes.

Chicken microchromosomes are hyperacetylated, early replicating, and gene rich.

The chicken karyotype consists of 39 chromosomes of which 33 are classed as microchromosomes (MICs). MICs contain about one third of genomic DNA. The majority of mapped chicken genes are assigned to macrochromosomes (MACs), but a recent study indicated that CpG islands (CGIs), which are associated with most vertebrate genes, map predominantly to MICs. The present work establishes that chicken genes are concentrated on MICs by several criteria. Acetylated (lysine 5) histone H4, which is strongly correlated with the presence of genes, is highly enriched on MICs by immunocytochemistry. In addition, detailed analysis of chicken cosmids shows that CGI-like fragments are approximately six times denser on MICs than on MACs. Published mapping of randomly chosen genes by fluorescent in situ hybridization (FISH) also shows a significant excess of microchromosomal assignments. Finally, the finding that MICs replicate during the first half of S phase is also compatible with the suggestion that MICs represent gene-rich DNA. We use the cosmid data to predict that approximately 75% of chicken genes are located on microchromosomes. [The sequence data described in this paper have been submitted to the GenBank data library under accession nos. AJ001643 and AJ001644.]

The chicken as a model to study microchromosomes in birds: a review

The chicken as a model to study microchromosomes in birds: a review

Induction of microchromosomes by chemical carcinogens correlates with SV40-DNA amplification in SV40-transformed Chinese hamster cells.

Radiations and chemical carcinogens induce the amplification of viral DNA inserts and of their cellular flanking sequences in SV40-transformed Chinese hamster embryo cells. In the cell line CO60, the phenomenon is easily measured by in situ hybridization using SV40-DNA as a probe. We found that the appearance of microchromosomes (MC) in CO60 metaphases correlated well with the induction of SV40-DNA amplification (SDA) mediated in the same cells by chemical carcinogens. SDA and MC formation had the same inducers and were essentially transient phenomena whose occurrence and disappearance were simultaneous. The banding properties of MC and the respective time courses of induction of chromosome aberrations and MC formation/disappearance indicated that MC were not chromosome or chromatid breaks but rather acentric double minute-like chromosomes. Double minute chromosomes (DM) have been shown to contain amplified genes. They specifically occur in established cell lines and in vivo tumor cells. Therefore, the reported correlations between SDA and MC formation and the homologies between MC and DM in CO60 cells further support the existence of specific relationships between mutagenesis, gene amplification, in vivo selective pressures and tumor cytogenetics.

Karyotype study of 5 species of Costa Rican snakes of the colubrid family

The karyotypes of five species of colubrid snakes from Costa Rica are as follows: Imantodes cenchoa and Drymobius margaritiferus have a diploid number of 36, with 16 macro- and 20 microchromosomes. The fourth pair is heteromorphic in females of I. cenchoa, with a metacentric Z and a submetacentric W chromosomes. Karyotypes of Erythrolampius bizonus and Leimadophis epinephalus have 28 chromosomes, without a clearcut separation between macro- and microchromosomes. In the case of E. bizomus, the fourth pair contains the sex chromosomes Z and W, both are submetacentric, but the W is smaller. Xenedon rabdocephalus has a diploid number of 34 chromosomes (22 macro- and 12 microchromosomes); pair 3 is heteromorphic in females, with a submetacentric Z and a smaller metacentric W. The karyotype of X. rabdocephalus may be derived from a primitive karyotype by means of reduction in the number of microchromosomes and centric fissions of two pairs of metacentric autosomes.

A comment on the paper: Recurrence of Down Syndrome Associated with Microchromosome by C. Ramos, L. Rivera, J. Benitez, E. Tejedor, and A. Sanchez-Cascos.

A comment on the paper: Recurrence of Down Syndrome Associated with Microchromosome by C. Ramos, L. Rivera, J. Benitez, E. Tejedor, and A. Sanchez-Cascos.