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At least 1,621 records · Page 90Linked to original sources
PubMed1999

Supernumerary chromosome variation, heteromorphic sex chromosomes and banding patterns in microteiid lizards of the genus Micrablepharus (Squamata, Gymnophthalmidae)

Cytogenetic investigations using differential staining (C-, replication R-banding and Ag-NOR staining) were performed in the two known species of the microteiid lizards of the genus Micrablepharus: M. maximiliani and M. atticolus. M. atticolus showed diploid number variation (2n = 50, 51, 52, 53) due to a system of supernumerary chromosomes which presented late replication patterns and differences in morphology (metacentric and submetacentric) and size. M. maximiliani revealed three different cytotypes (I, II and III) in a sample of only three animals. Two of them (cytotypes I and III) had 2n = 50, and the other (cytotype II) showed 2n = 51, with one B chromosome, all of them with difference in the number of autosome arms. A comparative analysis of the basic karyotype of M. atticolus (2n = 50) and the three cytotypes of M. maximiliani revealed differences in the number of biarmed and uniarmed chromosomes, probably due to several pericentric inversions. The genus Micrablepharus exhibited a remarkable variability in number and location of Ag-NORs including single and multiple NOR-bearing chromosome pairs. Variation of C-banding patterns was found in M. maximiliani and M. atticolus and that seems to be related to a species-specific trait. Sex determination of the XX:XY type was observed for both species.

Animals↗
PubMed1999

An easy and reliable procedure of microdissection technique for the analysis of chromosomal breakpoints and marker chromosomes.

Microdissection in combination with reverse painting fluorescence in-situ hybridization (FISH) is a very effective method to identify breakpoints and rearrangements of derived chromosomes and reveal the chromosomal origin of marker chromosomes. We describe an innovation that allows a convenient, fast and safe isolation of microdissected fragments as currently available protocols. The microdissected chromosomes are harvested in a collection drop located in a movable micropipette adjusted to a second micromanipulator under microscopic observation. We used this technique to analyze several cytogenetic aberrations. In order to evaluate the efficiency of our microdissection procedure, we compared the results obtained with microdissection probes made from only one fragment with those obtained with more than six microdissected fragments. In all cases, the single-fragment microdissections were sufficient to provide probes.

Chromosome Painting↗
PubMed2001

Visualization of the terminal structure of rice chromosomes 6 and 12 with multicolor FISH to chromosomes and extended DNA fibers.

High-resolution fluorescence in situ hybridization (FISH) on interphase and pachytene nuclei, and extended DNA fibers enabled microscopic distinction of DNA sequences less than a few thousands of base pairs apart. We applied this technique to reveal the molecular organization of telomere ends in japonica rice (Oryza sativa ssp. japonica), which consist of the Arabidopsis type TTTAGGG heptameric repeats and the rice specific subtelomeric tandem repeat sequence A (TrsA). Southern hybridizations of DNA digested with Bal31 and EcoRI, and FISH on chromosomes and extended DNA fibers demonstrated that (1) all chromosome ends possess the telomere tandem repeat measuring 3-4 kb; (2) the subtelomeric TrsA occurs only at the ends of the long arms of chromosomes 6 and 12, and measure 6 and 10 kb, which corresponds to 231 and 682 copies for these sites, respectively; (3) the telomere and TrsA repeats are separated by at most a few thousands of intervening nucleotide sequences. The molecular organization for a general telomere organization in plant chromosomes is discussed.

Chromosome Painting↗
PubMed2000

Robertsonian polymorphism, B chromosomes variation and sex chromosomes heteromorphism in the african water rat Dasymys (Rodentia, Muridae).

Chromosome banding analysis (G- and C-bands) of Dasymys rufulus from Senegal, Mali and the Ivory Coast, and D. cf. incomtus from Eastern and South-western Ethiopia was carried out. The diploid numbers (2N) in the former species range between 36 and 39 due to the presence of 0-3 small biarmed heterochromatic B chromosomes, resulting in a corresponding variation of the number of autosomal arms (NFa) between 44 and 50. The basic autosomal set was, however, constant and identical in these specimens. The karyotypes of D. cf. incomtus from Eastern and Western Ethiopia were found to be different (2N = 40 and 38, respectively). Comparison of G-banding patterns of the species studied revealed that they differ from each others by 1-2 Rb fusions/fissions, one paracentric inversion and heteromorphous sex chromosomes resulting from addition/deletion of heterochromatic blocks (X) and pericentric inversion (Y). In the light of the available chromosome banding data, the significance of intraspecies karyotypic variability within D. cf. incomtus and its relevance to the systematics of the genus are discussed.

Africa↗
PubMed2004

Chromosome evolution in bears: reconstructing phylogenetic relationships by cross-species chromosome painting.

Genome-wide homology maps among dog (Canis familiaris, CFA, 2n = 78), African lion (Panthera leo, PLE, 2n = 38), clouded leopard (Neofelis nebulosa, NNE, 2n = 38) and Malayan sun bear (Helartos malayanus, HMA, 2n = 74) have been established by chromosome painting using a complete set of dog probes. In total, chromosome-specific painting probes from the 38 dog autosomes reveal 69, 69 and 73 conserved segments in African lion, clouded leopard and Malayan sun bear, respectively. The chromosomal painting results show that the African lion and clouded leopard have an identical karyotype which, in turn, is similar to that previously published for the cat (Felis catus, FCA 2n = 38). The findings confirm and extend other studies that show felids to be karyotypically conserved. In contrast, ursids, including the Malayan sun bear, have a relatively highly rearranged karyotype in comparison with other carnivores. The 2n = 74 karyotype of the Malayan sun bear, which is believed to closely resemble the ancestral karyotype of the Ursidae, could have evolved from the 2n = 42 putative ancestral carnivore karyotype by an inversion and 16 centric fissions. Independent fusions of the acrocentric ancestral chromosomes have generated the unique karyotypes of the giant panda and the spectacled bear.

Animals↗
PubMed2004

Generation of chromosome painting probes from single chromosomes by laser microdissection and linker-adaptor PCR.

Fluorescence in situ hybridization (FISH) plays an essential role in research and clinical diagnostics. The versatility and resolution of FISH depends critically on the probe set used. Here, we describe an improved approach for the generation of specific DNA probes from single copies of chromosomes. Single chromosomes or single chromosomal regions were microdissected by laser pressure catapulting and amplified using linker-adaptor PCR. The probes were labeled and tested in various scenarios including multicolor-FISH experiments employing up to seven different fluorochromes. FISH confirmed the specific and even staining of the respective chromosomal regions. Furthermore, the capability of these probes to detect even small translocations (<3 Mb) suggests that the dissected regions are completely represented in the generated painting probes.

Chromosome Painting↗
PubMed2004

TSPY, the candidate gonadoblastoma gene on the human Y chromosome, has a widely expressed homologue on the X - implications for Y chromosome evolution.

TSPY, a candidate gene for a factor that promotes gonadoblastoma formation (GBY), is a testis-specific multicopy gene family in the male-specific region of the human Y (MSY) chromosome. Although it was originally proposed that male-specific genes on the Y originated from a transposed copy of an autosomal gene (Lahn & Page 1999b), at least two male-specific genes (RBMY and SRY) descended from a formerly recombining X-Y identical gene pair. Here we show that a TSPY homologue with similar gene structure lies in conserved positions, close to SMCX, on the X chromosome in human (TSPX ) and mouse (Tspx). TSPX is widely expressed and subject to X inactivation. TSPX and TSPY therefore evolved from an identical gene pair on the original mammalian sex chromosomes. This supports the hypothesis that even male-specific genes on the Y chromosome may have their origin in ubiquitously expressed genes on the X. It also strengthens the case for TSPY as a candidate for GBY, since independent functional studies link TSPX to cell cycle regulation.

Amino Acid Sequence↗
PubMed1997

Ovarian cancer has frequent loss of heterozygosity at chromosome 12p12.3-13.1 (region of TEL and Kip1 loci) and chromosome 12q23-ter: evidence for two new tumour-suppressor genes.

Identification of the key genetic alterations leading to ovarian cancer is in its infancy. Polymerase chain reaction (PCR)-based analysis of loss of heterozygosity (LOH) is a powerful method for detecting regions of altered tumour-suppressor genes. Focusing on chromosome 12, we examined 23 ovarian cancer samples for LOH using 31 highly polymorphic microsatellite markers and found the chromosomal localization of two putative tumour-suppressor genes. Two commonly deleted regions were 12p12.3-13.1 in 6/23 (26%) and 12q23-ter in 7/23 (30%) samples. LOH on chromosome 12 was more common in late-stage ovarian carcinomas. The region of LOH at 12p12.3-13.1 includes the genes that code for the ETS-family transcriptional factor, known as TEL, and the cyclin-dependent kinase inhibitor, known as p27Kip1. Mutational analysis of both TEL and p27Kip1 using single-strand conformation polymorphism (SSCP) showed no abnormalities, suggesting that the altered gene in this region is neither of these genes. Taken together, our data suggest that new tumour-suppressor genes in the region of chromosomes 12p12.3-13.1 and 12q23-ter may be involved in the development of ovarian cancer.

Adenocarcinoma↗
PubMed2001

Chromosomal instability in chromosome band 12p13: multiple breaks leading to complex rearrangements including cytogenetically undetectable sub-clones.

During fluorescence in situ hybridization (FISH) analysis of metaphase cells from 70 patients with lymphoid and myeloid hematologic malignancies and chromosomal rearrangements involving band 12p13, we identified nine patients (four with lymphoid malignancies, four with myeloid malignancies and one with biphenotypic leukemia) who showed more complicated rearrangements than we had expected from conventional cytogenetic study. In six patients, multiple breaks occurred in small segments of 12p with subsequent translocations and insertions of these segments into other chromosomes, sometimes to unexpected regions. In three patients additional chromosome breaks resulted in a sub-clone which was cytogenetically indistinguishable from the main clone in each patient based on the cytogenetic analysis. These subtle molecular events were detected exclusively in a region covering TEL/ETV6 and KIP1/CDKN1B. Seven of nine had a previous history of chemo/radiotherapy; all the patients showed complex karyotypes, even though they were newly diagnosed with leukemia. Survival data were available in five patients, and all survived less than 6 months. These findings suggest that the 12p13 region, especially the above-mentioned region, is genetically unstable and fragile. It is likely that multiple chromosome breaks were induced through mutagens used in chemo/ radiotherapy, and are associated with a sub-group of patients with an extremely bad prognosis.

Chromosome Fragility↗
PubMed1999

Physical assignments of human chromosome 13 genes on pig chromosome 11 demonstrate extensive synteny and gene order conservation between pig and human.

Previous mapping between the human and pig genomes suggested extensive conservation of human chromosome 13 (HSA13) to pig chromosome 11 (SSC11). The objectives of this study were comparative gene mapping of pig homologs of HSA13 genes and examining gene order within this conserved synteny group by physical assignment of each locus. A detailed HSA13 to SSC11 comparison was chosen since the comparative gene map is not well developed for these chromosomes and a rearranged gene order within conserved synteny groups was observed from the comparison between HSA13 and bovine chromosome 12 (BTA12). Heterologous primers for PCR were designed and used to amplify pig homologous fragments. The pig fragments were sequenced to confirm the homology. Six pig STSs (FLT1, ESD, RB1, HTR2A, EDNRB, and F10) were physically mapped using a somatic cell hybrid panel to SSC11, and fluorescent in situ hybridization (FISH) mapping was also applied to improve map resolution and determine gene order. Results from this study increase the comparative information available on SSC11 and suggest a conserved gene order on SSC11 and HSA13, in contrast to human:bovine comparisons of this syntenic group.

Animals↗
PubMed1985

Nucleotide sequence of a t(14;18) chromosomal breakpoint in follicular lymphoma and demonstration of a breakpoint-cluster region near a transcriptionally active locus on chromosome 18.

The t(14;18)(q32;21) chromosomal translocation characteristic of follicular lymphomas is the most common cytogenetic abnormality known to be associated with any specific type of hematolymphoid malignancy. A fragment of DNA containing the crossover point between chromosomes 14 and 18 was cloned from the tumor cells of a patient with a follicular lymphoma carrying this translocation. Nucleotide sequence analysis of the breakpoint DNA revealed that the break in chromosome 14 occurred in joining region 4(J4) of the nonfunctional immunoglobulin heavy chain allele. This finding and other structural similarities of the breakpoint with the functional diversity region-joining region (D-J) joint in this lymphoma suggest that D-J recombination enzymes played a role in the mechanism of the t(14;18) translocation. Hybridization analysis of DNA from 40 follicular lymphomas showed that the majority of t(14;18) translocations occur on chromosome 18 DNA within 4.2 kilobases of the cloned breakpoint. A DNA probe from this breakpoint-cluster region detects transcription products in the tumor cells from which it was cloned and in a B-lymphoma cell line containing a t(14;18) translocation.

Alleles↗
PubMed1991

Integrative selection of human chromosome-specific yeast artificial chromosomes.

Human specific "integrative selection vectors" (ISVs) were designed to optimize integration of a yeast-selectable marker specifically into yeast artificial chromosomes (YACs) derived from human but not mouse DNA. ISVs were transformed into a YAC genomic library constructed from DNA of a human-mouse somatic cell hybrid containing chromosome 21 (HSA21) as the only human chromosome. One percent of the yeast in the original library contained HSA21-derived YACs; between 45% and 54% of the yeast recovered after transformation with ISV vectors contained human YACs. Integrative selection provides a rapid means of obtaining a highly enriched population of human chromosome-specific YACs by eliminating the labor-intensive steps of isolating and screening primary transformants. The procedure is biased toward the selection of YACs that contain a large number of targets for homologous recombinations; thus, libraries constructed by this procedure will be composed primarily of the largest YACs in the population.

Chromosomes, Fungal↗
PubMed1995

Metaphase chromosome analysis by ligation-mediated PCR: heritable chromatin structure and a comparison of active and inactive X chromosomes.

We report that ligation-mediated PCR (LMPCR) can be used for high-resolution study of metaphase chromosomes, and we discuss the role of metaphase chromatin structure in the preservation of differentiated cell states. The X chromosome-linked human PGK1 (phosphoglycerate kinase 1) promoter region was investigated, and euchromatic active X chromosome (Xa) metaphase chromatin was compared with interphase Xa chromatin and to heterochromatic inactive X chromosome (Xi) metaphase and interphase chromatin. We find that (i) good-quality data at single-nucleotide resolution can be obtained by LMPCR analysis of dimethyl sulfate-treated intact metaphase cells; (ii) transcription factors present on the Xa promoter of interphase chromatin are not present on metaphase chromatin, establishing that the transcription complex on the PGK1 promoter must form de novo each cell generation; and (iii) the dimethyl sulfate reactivity pattern of Xa and Xi chromatin at metaphase is very similar to that of naked DNA. These results are discussed in the context of models for heritable chromatin structure and epigenetic mechanisms for cell memory, and they are also relevant to more general aspects of chromatin structure and differences between euchromatin and heterochromatin.

Animals↗
PubMed1999

Human artificial chromosomes generated by modification of a yeast artificial chromosome containing both human alpha satellite and single-copy DNA sequences.

A human artificial chromosome (HAC) vector was constructed from a 1-Mb yeast artificial chromosome (YAC) that was selected based on its size from among several YACs identified by screening a randomly chosen subset of the Centre d'Etude du Polymorphisme Humain (CEPH) (Paris) YAC library with a degenerate alpha satellite probe. This YAC, which also included non-alpha satellite DNA, was modified to contain human telomeric DNA and a putative origin of replication from the human beta-globin locus. The resultant HAC vector was introduced into human cells by lipid-mediated DNA transfection, and HACs were identified that bound the active kinetochore protein CENP-E and were mitotically stable in the absence of selection for at least 100 generations. Microdissected HACs used as fluorescence in situ hybridization probes localized to the HAC itself and not to the arms of any endogenous human chromosomes, suggesting that the HAC was not formed by telomere fragmentation. Our ability to manipulate the HAC vector by recombinant genetic methods should allow us to further define the elements necessary for mammalian chromosome function.

Cell Line↗
PubMed1994

Heterogeneity of chromosome damage in beta-thalassaemia traits. An evaluation of spontaneous and gamma-ray-induced micronuclei and chromosome aberrations in lymphocytes in vitro after G0 and G2 phase irradiation.

This study is an attempt to evaluate the chromosomal radiosensitivity of beta-thalassaemia traits compared with healthy individuals from the general population, necessitated by the fact that beta-thalassaemia trait is present in 1-17% of different population groups in India and the chances of encountering them in radiation and chemical related industries do exist. Spontaneous chromosome aberration frequencies in peripheral blood lymphocytes from beta-thalassaemia traits were found to be in the normal range, whereas significantly higher frequencies of micronuclei (MN) were observed in thalassaemia traits. Based on MN frequency at 2 Gy, beta-thalassaemia traits fall into two distinct categories. A hypersensitive group with significant increase in radiation-induced MN over the control group, and a second group with MN frequency slightly above normal individuals. Even when compared with the fitted data at 2 Gy obtained from the pooled results of extensive dose-response investigations from 0.5-5 Gy gamma-rays with normal donors for MN, dicentrics and total aberrations, the difference between the means of MN frequencies in beta-thalassaemia traits and normals is significant. MN have a higher control level, a higher value for the alpha component, and much lower value for the beta component, when compared with total aberrations. Both in 2-Gy irradiated G0 lymphocytes as well as 0.5 and 1-Gy irradiated G2 lymphocytes, there is a certain degree of hypersensitivity when the results are meaned over a number of individuals, but some individuals overlap within the normal range. In G0 irradiated lymphocytes from beta-thalassaemia traits, the dicentric chromosome is the only aberration category in which the yield is seen to rise. The heterogeneity in chromosomal radiosensitivity observed in beta-thalassaemia traits is discussed in terms of the oxidative damage consequent to the genetic and biochemical features peculiar to the beta-thalassaemia trait cell. The data presented herein may have wider implications in radiation protection.

Chromosome Aberrations↗
PubMed1997

Detection of radiation-induced chromosome aberrations using fluorescence in situ hybridization in drug-induced premature chromosome condensations of tumour cell lines with different radiosensitivities.

A potential assay for radiosensitivity of human tumours is that of radiation-induced chromosome damage determined on metaphase spreads of human solid tumours. It is often difficult, however, to obtain enough metaphases for cytogenetic analysis after radiation. A possible solution would be to use the technique of premature chromosome condensation (PCC), enabling the study of interphase cells. The induction of PCCs using mitotic inducer cells is technically difficult, however, and the frequency of induction relatively low. We have attempted to use another approach, to induce PCCs using the phosphatase inhibitors okadaic acid and calyculin A. Both inhibitors were found to induce PCCs in several human tumour cell lines, with calyculin A producing the higher incidence. Determination of radiation-induced chromosome aberrations using fluorescence in situ hybridization on these chemically induced PCCs showed a clear difference between a radiosensitive (SCC61) and a radioresistant (A549) tumour cell line, with more aberrations in the sensitive line. Owing to incomplete condensation compared with that in standard metaphases, accurate classification of aberration types was not possible. Despite this limitation, the present data indicate that this relatively quick and simple method may be useful for determining chromosome aberrations in interphase cells and potentially in human solid tumours for predictive assay purposes.

Animals↗
PubMed1999

HCP-1, a protein involved in chromosome segregation, is localized to the centromere of mitotic chromosomes in Caenorhabditis elegans.

To learn more about holocentric chromosome structure and function, we generated a monoclonal antibody (mAb), 6C4, that recognizes the poleward face of mitotic chromosomes in Caenorhabditis elegans. Early in mitosis, mAb 6C4 stains dots throughout the nucleoplasm. Later in prophase, mAb 6C4 stains structures on opposing faces of chromosomes which orient towards the centrosomes at metaphase. Colocalization with an antibody against a centromeric histone H3-like protein and the MPM-2 antibody, which identifies a kinetochore-associated phosphoepitope present in a variety of organisms, shows that the mAb 6C4 staining is present adjacent to the centromere. Expression screening using mAb 6C4 identified a protein in C. elegans that we named HCP-1 (for holocentric protein 1). We also identified a second protein from the C. elegans genome sequence database, HCP-2, that is 54% similar to HCP-1. When expression of HCP-1 is reduced by RNA interference (RNAi), staining with mAb 6C4 is eliminated, indicating that hcp-1 encodes the major mAb 6C4 antigen. RNAi with hcp-1 and hcp-2 together results in aberrant anaphases and embryonic arrest at approximately 100 cells with different amounts of DNA in individual nuclei. These results suggest that HCP-1 is a centromere-associated protein that is involved in the fidelity of chromosome segregation.

Amino Acid Sequence↗
PubMed1970

Chromosomal basis of dosage compensation in Drosophila. 3. Early completion of replication by the polytene X-chromosome in male: further evidence and its implications.

Thymidine-(3)H labeling patterns on the X (section 1 A to 12 E of Bridges' map) and 2 R (section 56 F to 60 F of Bridges' map) segments in the salivary gland chromosomes of Drosophila melanogaster have been analyzed in male and female separately. The observed patterns fit, with a few exceptions, in a continuous to discontinuous labeling sequence. In nuclei with similar labeling patterns on the 2R segment in both sexes, the number of labeled sites on the X in male is always less than in female X's. The labeling frequency of the different sites on the male X is considerably lower than those on the female X's, while the sites on the 2R segment have very similar frequency in the two sexes. The rate of thymidine-(3)H incorporation (as judged by visual grain counting) is relatively higher in male X than in female X's. It is concluded that the model sequence of replication in polytene chromosomes follows a continuous to discontinuous labeling sequence, and that the single X in male completes its replication earlier than either the autosomes in male or the X's in female. This asynchronous and faster rate of replication by the polytene X-chromosome in male substantiates the hypothesis of hyperactivity of the single X in male as the chromosomal basis of dosage compensation in Drosophila.

Animals↗