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H Scherthan

Publications and source records attributed to H Scherthan.

At least 55 records · Page 3Linked to original sources
PubMed1997

Segmental homology among cattle (Bos taurus), Indian muntjac (Muntiacus muntjak vaginalis), and Chinese muntjac (M. reevesi) karyotypes.

In an attempt to examine homologies between Indian and Chinese muntjac karyotypes at a subchromosomal level, five bovine cosmids were comparatively mapped by heterologous fluorescence in situ hybridization (FISH). In the Indian muntjac (2n = 6) all cosmids mapped to chromosome 1, whereas in the Chinese muntjac (2n = 46) two cosmids mapped to chromosome 3 and one cosmid each mapped to chromosomes 1, 7, and 17. These markers have maintained their intrachromosomal position relative to a centromere/telomere axis in cattle and in Chinese and Indian muntjac chromosomal arms. Our results corroborate the tandem-fusion hypothesis for muntjac karyotypic evolution and establish orientational homology between the involved Chinese muntjac chromosomes and the discrete segments on Indian muntjac chromosome 1. Furthermore, our data disclose regional homologies between cattle and muntjac genomes and demonstrate the validity of intergeneric cosmid-FISH for investigations on karyotype evolution.

Animals↗
PubMed1996

Zoo-FISH delineates conserved chromosomal segments in horse and man.

Human chromosome specific libraries (CSLs) were individually applied to equine metaphase chromosomes using the fluorescence in situ hybridization (FISH) technique. All CSLs, except Y, showed painting signals on one or several horse chromosomes. In total 43 conserved chromosomal segments were painted. Homoeology could not, however, be detected for some segments of the equine genome. This is most likely related to the very weak signals displayed by some libraries, rather than to the absence of similarity with the human genome. In spite of divergence from the human genome, dated 70-80 million years ago, a fairly high degree of synteny conservation was observed. In seven cases, whole chromosome synteny was detected between the two species. The comparative painting results agreed completely with the limited gene mapping data available in horses, and also enabled us provisionally to assign one linkage group (U2) and one syntenic group (NP, MPI, IDH2) to specific equine chromosomes. Chromosomal assignments of three other syntenic groups are also proposed. The findings of this study will be of significant use in the expansion of the hitherto poorly developed equine gene map.

Animals↗
PubMed1996

A comparative map of the porcine and human genomes demonstrates ZOO-FISH and gene mapping-based chromosomal homologies.

ZOO-FISH with chromosome-specific DNA libraries (CSLs) from individual flow-sorted human chromosomes was applied on porcine metaphase chromosomes to establish segment homology between the pig and human karyotypes. Forty-seven porcine chromosomal segments corresponding to all human chromosomes except the Y were delineated, resulting in a nearly complete coverage of the porcine karyotype. The syntenic segments detected were further confirmed by the gene mapping information available in the two species. A map demarcating physical boundaries of human homologies on individual pig chromosomes is complemented with a detail survey of the physical and genetic linkage mapping data in the two species. The resultant map, thus, provides a comprehensive and updated comparative status of the human and porcine genomes.

Animals↗
PubMed1996

Comparative analysis of the cattle and human genomes: detection of ZOO-FISH and gene mapping-based chromosomal homologies.

Comparative chromosome painting with individual human chromosome-specific libraries (CSLs) on cattle metaphase chromosomes delineated 46 homologous chromosomal segments between the two species. Continuous arrangement of these segments on individual cattle chromosomes demonstrates a nearly complete coverage of the bovine karyotype and shows physical boundaries of bovine chromosomal segments homologous to individual human chromosomes. Alignment of the available comparative gene mapping data with the homologous segments strongly supports the detected gross homologies between the karyotypes of the two species. In addition to cattle, four human CSLs were hybridized to sheep metaphase chromosomes also, to further verify the known karyotype homology within the Bovidae. Besides its application to karyotype evolution research, the comparative knowledge provides for rapid expansion of the much needed Type I locus-based bovine gene map.

Animals↗
PubMed1996

Centromere and telomere movements during early meiotic prophase of mouse and man are associated with the onset of chromosome pairing.

The preconditions and early steps of meiotic chromosome pairing were studied by fluorescence in situ hybridization (FISH) with chromosome-specific DNA probes to mouse and human testis tissue sections. Premeiotic pairing of homologous chromosomes was not detected in spermatogonia of the two species. FISH with centromere- and telomere-specific DNA probes in combination with immunostaining (IS) of synaptonemal complex (SC) proteins to testis sections of prepuberal mice at days 4-12 post partum was performed to study sequentially the meiotic pairing process. Movements of centromeres and then telomeres to the nuclear envelope, and of telomeres along the nuclear envelope leading to the formation of a chromosomal bouquet were detected during mouse prophase. At the bouquet stage, pairing of a mouse chromosome-8-specific probe was observed. SC-IS and simultaneous telomere FISH revealed that axial element proteins appear as large aggregates in mouse meiocytes when telomeres are attached to the nuclear envelope. Axial element formation initiates during tight telomere clustering and transverse filament-IS indicated the initiation of synapsis during this stage. Comparison of telomere and centromere distribution patterns of mouse and human meiocytes revealed movements of centromeres and then telomeres to the nuclear envelope and subsequent bouquet formation as conserved motifs of the pairing process. Chromosome painting in human spermatogonia revealed compacted, largely mutually exclusive chromosome territories. The territories developed into long, thin threads at the onset of meiotic prophase. Based on these results a unified model of the pairing process is proposed.

Animals↗
PubMed1996

The clustering of telomeres and colocalization with Rap1, Sir3, and Sir4 proteins in wild-type Saccharomyces cerevisiae.

We have developed a novel technique for combined immunofluorescence/in situ hybridization on fixed budding yeast cells that maintains the three-dimensional structure of the nucleus as monitored by focal sections of cells labeled with fluorescent probes and by staining with a nuclear pore antibody. Within the resolution of these immunodetection techniques, we show that proteins encoded by the SIR3, SIR4, and RAP1 genes colocalize in a statistically significant manner with Y' telomere-associated DNA sequences. In wild-type cells the Y' in situ hybridization signals can be resolved by light microscopy into fewer than ten foci per diploid nucleus. This suggests that telomeres are clustered in vegetatively growing cells, and that proteins essential for telomeric silencing are concentrated at their sites of action, i.e., at telomeres and/or subtelomeric regions. As observed for Rap1, the Sir4p staining is diffuse in a sir3- strain, and similarly, Sir3p staining is no longer punctate in a sir4- strain, although the derivatized Y' probe continues to label discrete sites in these strains. Nonetheless, the Y' FISH is altered in a qualitative manner in sir3 and sir4 mutant strains, consistent with the previously reported phenotypes of shortened telomeric repeats and loss of telomeric silencing.

Antibody Specificity↗
PubMed1996

Detection of complex genetic alterations in human glioblastoma multiforme using comparative genomic hybridization.

The aim of the present study was to detect complex genetic alterations in human glioblastoma multiforme (GBM) by comparative genomic in situ hybridization (CGH). Of the 24 GBM that were examined, increased fluorescence intensities indicating chromosomal polysomy of chromosome 7 and gene amplification at chromosome 7p were found in 42% of the tumors. In addition, signal enhancement of chromosome 19 was present in 29% and at 12q13-15 in 21% of the tumors. We also detected reduction of fluorescence intensities indicating gross deletions on chromosomes 10 (58%), 9p (46%), and 13 (29%). There was a close correlation of CGH results when compared with Southern analysis of the EGFR gene localized on chromosome 7 and loss of heterozygosity detection of chromosome 9 and 10 by microsatellite PCR. A close correlation was also observed between copy number changes of chromosome 7 and deletions of chromosome 10. Amplification of chromosome 12q and deletions of chromosomes 9p and 13 seemed to be complementary in the tumors investigated in the present study.

Adult↗
PubMed1996

Comparative genomic hybridization (CGH) discloses chromosomal and subchromosomal copy number changes in Merkel cell carcinomas.

We analyzed three Merkel cell carcinomas (MCC), applying comparative genomic hybridization (CGH) with DNA from paraffin-embedded and cultured tumor material as the probes. By this method, numerous changes in chromosome copy numbers were observed in each tumor investigated. Recurrent gains of chromosomes 1, 6, 18q and 20 were detected in two tumors. A third tumor showed complex chromosomal copy number changes, including gain of chromosome 8 and 9. These gains, as well as gain of chromosome 1 in the first two tumors, were confirmed by fluorescence in situ hybridization to paraffin tissue sections. Our results support the view that important genes for MCC development may be located on chromosomes 1, 6, 18q and 20.

Aged↗
PubMed1996

Increased specificity of colloidal silver staining by means of chemical attenuation.

A modification of the silver staining procedure of Howell and Black (1980) is reported which makes use of teleostean gelatin as protective colloid and renders a high signal-to-noise ratio. We demonstrate that this ratio can be further increased by subsequent attenuation with a chemical reducer consisting of a mixture of potassium ferricyanide (III) and sodium thiosulphate. It is shown that slight changes of the concentration of the reactive compounds of the chemical reducer make the protocol applicable to human, plant (Aliium cepa, Rhinanthus minor) as well as meiotic insect (Acheta domesticus) chromosome preparations. Due to its broad applicability, the method could find utilization in studies on chromatin and chromosome functions in many species.

Animals↗
PubMed1995

Comparative genomic in situ hybridization of colon carcinomas with replication error.

The aim of the present study was to detect complex genetic alterations in colorectal carcinomas with and without microsatellite instability (MIN) by comparative genomic in situ hybridization. MIN due to replication errors is the hallmark of hereditary nonpolyposis colon cancer. None of 6 MIN-positive tumors showed amplifications, and only 2 tumors displayed deletions of one chromosomal segment each. In contrast, different gains and losses were observed in 11 of 12 MIN-negative carcinomas. The most frequent gains affected chromosomes 7, 13, and 20q, whereas deletions were observed on chromosomes 17, 18, and 9p. These results demonstrate different mechanisms of genetic instability in subgroups of colorectal carcinomas and may, therefore, support the hypothesis of different etiologies in tumors with and without MIN.

Adult↗
PubMed1995

Roles for two RecA homologs in promoting meiotic chromosome synapsis.

Previous studies have shown that the RAD51 and DMC1 genes of Saccharomyces cerevisiae encode homologs of the Escherichia coli RecA strand exchange enzyme. Results presented here demonstrate that the dmc1 and rad51 mutants undergo nearly complete chromosome synapsis, but synaptonemal complex formation is delayed substantially compared with wild type. In the zip1 mutant, chromosomes are paired homologously, but not synapsed, and the protein backbones (axial elements) of each pair of chromosomes are connected intimately to each other at a few sites referred to herein as axial associations. dmc1 zip1 and rad51 zip1 double mutants assemble axial elements that are not obviously associated, demonstrating that the Dmc1 and Rad51 proteins are required to establish or stabilize axial associations. We propose that axial associations serve to promote meiotic chromosome synapsis and that the absence of these associations accounts for the delayed and inefficient synapsis observed in dmc1 and rad51 strains. During meiosis in haploid yeast, chromosome synapsis takes place between nonhomologous chromosome segments. In a zip1 haploid, axial associations are not apparent, suggesting that these associations depend on interactions between homologous sequences.

Alleles↗
PubMed1995

Suppression of tumorigenicity of breast cancer cells by transfer of human chromosome 17 does not require transferred BRCA1 and p53 genes.

A number of candidate tumor suppressor genes located on the human chromosome 17 are thought to have a role to play in the development of breast cancer. In addition to the p53 gene on 17p13.1 and the BRCA1 gene mapped to 17q12-21, other chromosomal regions for tumor suppressor genes have been suggested to exist on 17p13.3 and both the central and the distal parts of 17q, although definitive functional proof of their involvement in breast cancer tumorigenesis is still lacking. In this report we show that microcell transfer of a human chromosome 17 into wild-type p53 breast cancer cells CAL51 results in loss of tumorigenicity and anchorage-independent growth, changes in cell morphology and a reduction of cell growth rates of the neo-selected microcell hybrids. In the hybrid cells, which express the p53 wild-type protein, only the p- and the distal parts of the q arm of donor chromosome 17 are transferred. Thus, our results provide functional evidence for the presence of one or more tumor suppressor gene(s) on chromosome 17, which are distinct from the p53 and the BRCA1 genes.

Animals↗
PubMed1995

Morphology of a human-derived YAC in yeast meiosis.

In meiosis of human males DNA is packaged along pachytene chromosomes about 20 times more compactly than in meiosis of yeast. Nevertheless, a human-derived yeast artificial chromosome (YAC) shows the same degree of compaction of DNA as endogenous chromosomes in meiotic prophase nuclei of yeast. This suggests that in yeast meiosis, human and yeast DNA adopt a similar organization of chromatin along the pachytene chromosome cores. Therefore meiotic chromatin organization does not seem to be an inherent chromosomal property but is governed by the host-specific cellular environment. We suggest that there is a correlation between the less dense DNA packaging and the increased rate of recombination that has been reported for human-derived YACs as compared with human DNA in its natural environment.

Chromosomes, Artificial, Yeast↗
PubMed1995

The yeast MER2 gene is required for chromosome synapsis and the initiation of meiotic recombination.

Mutation of the MER2 gene of Saccharomyces cerevisiae confers meiotic lethality. To gain insight into the function of the Mer2 protein, we have carried out a detailed characterization of the mer2 null mutant. Genetic analysis indicates that mer2 completely eliminates meiotic interchromosomal gene conversion and crossing over. In addition, mer2 abolishes intrachromosomal meiotic recombination, both in the ribosomal DNA array and in an artificial duplication. The results of a physical assay demonstrate that the mer2 mutation prevents the formation of meiosis-specific, double-strand breaks, indicating that the Mer2 protein acts at or before the initiation of meiotic recombination. Electron microscopic analysis reveals that the mer2 mutant makes axial elements, which are precursors to the synaptonemal complex, but homologous chromosomes fail to synapse. Fluorescence in situ hybridization of chromosome-specific DNA probes to spread meiotic chromosomes demonstrates that homolog alignment is also significantly reduced in the mer2 mutant. Although the MER2 gene is transcribed during vegetative growth, deletion or overexpression of the MER2 gene has no apparent effect on mitotic recombination or DNA damage repair. We suggest that the primary defect in the mer2 mutant is in the initiation of meiotic genetic exchange.

Chromosomes, Fungal↗
PubMed1995

Heteroduplex DNA formation and homolog pairing in yeast meiotic mutants.

Previous studies of Saccharomyces cerevisiae have identified several meiosis-specific genes whose products are required for wild-type levels of meiotic recombination and for normal synaptonemal complex (SC) formation. Several of these mutants were examined in a physical assay designed to detect heteroduplex DNA (hDNA) intermediates in meiotic recombination. hDNA was not detected in the rec102, mei4 and hop1 mutants; it was observed at reduced levels in red1, mek1 and mer1 strains and at greater than the wild-type level in zip1. These results indicate that the REC102, MEI4, HOP1, RED1, MEK1 and MER1 gene products act before hDNA formation in the meiotic recombination pathway, whereas ZIP1 acts later. The same mutants assayed for hDNA formation were monitored for meiotic chromosome pairing by in situ hybridization of chromosome-specific DNA probes to spread meiotic nuclei. Homolog pairing occurs at wild-type levels in the zip1 and mek1 mutants, but is substantially reduced in mei4, rec102, hop1, red1 and mer1 strains. Even mutants that fail to recombine or to make any SC or SC precursors undergo a significant amount of meiotic chromosome pairing. The in situ hybridization procedure revealed defects in meiotic chromatin condensation in mer1, red1 and hop1 strains.

Chromosomes, Fungal↗
PubMed1995

Analysis of sex chromosome distribution in the gonadal tissue of a 45,X/47,XYY mosaic by fluorescence in situ hybridization.

45,X/47,XYY mosaicism is a rare condition with scarce information on the tissue-specific distribution of the different cell lines. Fluorescence in situ hybridization with repetitive, chromosome-specific DNA probes was applied to gain insight into the tissue-specific distribution of the two cell lines in biopsies of the streak gonad and dysgenetic testis of a 2-year-old individual exhibiting 45,X/47,XYY mosaicism. The distribution of the 45,X/47,XYY cells within different tissues was found to be nonrandom. The coelomic epithelium, the vascular endothelium, and the prepuberal germ cells exhibited predominantly a 47,XYY karyotype. In contrast, Sertoli cells exhibited both karyotypes, and the remaining tissue was predominantly composed of 45,X cells. The contribution of the two cell lines to gonadal development is discussed.

Child, Preschool↗