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PubMed1988

Double minute chromosomes can be produced from precursors derived from a chromosomal deletion.

Recent experiments have shown that gene amplification can be mediated by submicroscopic, autonomously replicating, circular extrachromosomal molecules. We refer to those molecules as episomes (S. Carroll, P. Gaudray, M. L. DeRose, J. F. Emery, J. L. Meinkoth, E. Nakkim, M. Subler, D. D. Von Hoff, and G. M. Wahl, Mol. Cell. Biol. 7:1740-1750, 1987). The experiments reported in this paper explore the way episomes are formed and their fate in the cell over time. The data reveal that in our system the episomes are initially 250 kilobases, but gradually enlarge until they become double minute chromosomes. In addition, we show that episomes or double minute chromosomes can integrate into chromosomes. Our results also suggest that episomes can be produced by deletion of the corresponding sequences from the chromosome.

Animals↗
PubMed1998

Karyotype and chromosomal polymorphism of an undescribed Akodon from Central Brazil, a species with the lowest known diploid chromosome number in rodents.

The diploid chromosome number of 2n = 10 found in a new species of Akodon (Cricetidae, Rodentia) from two localities of the state of Mato Grosso, Central Brazil, represents the lowest chromosome number known for rodents. One female with nine chromosomes due to sex chromosome monosomy (2n = 9,XO) was also found. The karyotype comprises two large metacentric pairs (1 and 2); one large polymorphic pair (3), which could be acrocentric, submetacentric, or heterozygous as a result of a pericentric inversion; and one minute metacentric pair (4). The sex determination is of the XX/XY type. CBG, GTG, and RBG banding patterns, Ag-NORs, and meiotic data are presented. Fluorescence in situ hybridization with a (TTAGGG)7 repeat as a probe revealed interstitial telomeric bands (ITBs) in two of the large pairs.

Animals↗
PubMed2001

Chromosomal evolution in the vlei rat, Otomys irroratus (Muridae: Otomyinae): a compound chromosomal rearrangement separates two major cytogenetic groups.

G- and C-banding delimits two cytogenetic groups within the vlei rat, Otomys irroratus. One has a diploid number of 2n = 24, resulting from a centric fusion of chromosomes 7 and 12 of the O. irroratus standard coupled with a tandem fusion to chromosome 8. The second has a diploid number of 2n = 28, lacks the compound chromosome, and appears to have a far wider geographic distribution within South Africa. Additionally, the two groups differ through the presence of cytotype-specific heterozygous centric fusions and one to three B chromosomes which appear as floating polymorphisms in the 2n = 28 complex.

Animals↗
PubMed2001

Comparative architectural aspects of regions of conserved synteny on human chromosome 11p15.3 and mouse chromosome 7 (including genes WEE1 and LMO1).

Human chromosome 11p15.3 is associated with chromosome aberrations in the Beckwith Wiedemann Syndrome and implicated in the pathogenesis of different tumor types including lung cancer and leukemias. To date, only single tumor-relevant genes with linkage to this region (e.g. LMO1) have been found suggesting that this region may harbor additional potential disease associated genes. Although this genomic area has been studied for years, the exact order of genes/chromosome markers between D11S572 and the WEE1 gene locus remained unclear. Using the FISH technique and PAC clones of the flanking markers we determined the order of the genomic markers. Based on these clones we established a PAC contig of the respective region. To analyse the chromosome area in detail the synteny of the orthologous region on distal mouse chromosome 7 was determined and a corresponding mouse clone contig established, proving the conserved order of the genes and markers in both species: "cen-WEE1-D11S2043-ZNF143-RANBP7-CEGF1- ST5-D11S932-LMO1-D11S572-TUB-tel", with inverted order of the murine genes with respect to the telomere/centromere orientation. The region covered by these contigs comprises roughly 1.6 MB in human as well as in mouse. The genomic sequence of the two subregions (around WEE1 and LMO1) in both species was determined using a shotgun sequencing strategy. Comparative sequence analysis techniques demonstrate that the content of repetitive elements seems to decline from centromere to telomere (52.6% to 34.5%) in human and in the corresponding murine region from telomere to centromere (41.87% to 27.82%). Genomic organisation of the regions around WEE1 and LMO1 was conserved, although the length of gene regions varied between the species in an unpredictable ratio. CpG islands were found conserved in putative promoter regions of the known genes but also in regions which so far have not been described as harboring expressed sequences.

AT Rich Sequence↗
PubMed2004

Nondisjunction rates of mouse specific chromosomes involved in heterozygous Rb rearrangements measured by chromosome painting of spermatocytes II. I. The effects of the number of trivalents.

Dual-colour FISH painting with alternative fluorescent chromosome-specific probes allowed us to distinguish chromosomes 1, 4, 6 and 14. The purpose was to check whether nondisjunction rates of specific chromosomes involved in heterozygous Robertsonian fusions are independent of the number of trivalents, or an epistatic effect among Rb chromosomes takes place affecting nondisjunction rates. Probes were used on DAPI-stained metaphases of spermatocytes II of laboratory strains of mice with reconstructed karyotypes heterozygous for one, two, three or four Robertsonian metacentrics in an all-acrocentric background. The existence of such epistatic interactions was not verified.

Aneuploidy↗
PubMed2004

Different numbers of rye B chromosomes induce identical compaction changes in distinct A chromosome domains.

In rye each B chromosome (B) represents 5.5% of the diploid A genome. Rye Bs have several nuclear to whole plant effects although they seem to bear no genes except for the ones that lead to their maintenance within a population. In this context, and considering that rye Bs are enriched in repetitive non-coding regions that build up heterochromatin (het), we investigated the influence of Bs on the organization of two chromatin fractions, namely the ribosomal DNA (facultative het) and satellite (non-het) domain of rye chromosome 1 by silver staining on root tip metaphase cells. The results show that rye Bs cause condensation both in the NOR and in the chromosome 1 satellite domain. Since the silver staining technique used is indicative of the transcriptional activity of the NORs, the condensation observed at those loci demonstrates that the rRNA gene arrays are down-regulated in the presence of Bs, regardless of their number per individual. Furthermore, the organizational changes of metaphase NORs find parallel with the interphase organization of ribosomal chromatin, since the frequency of cells with intranucleolar condensed rDNA regions increases drastically and nuclear matrix attachment pattern is altered in the presence of the Bs. Our results show an identical effect of the Bs on the organization of two distinct chromosome domains displaying a presence/absence dichotomy.

Chromosomal Instability↗
PubMed2005

A dense comparative gene map between human chromosome 19q13.3-->q13.4 and a homologous segment of swine chromosome 6.

The human chromosome (HSA)19q region has been shown to correspond to swine chromosome (SSC) 6q11-->q21 by bi-directional chromosomal painting and gene mapping. However, since the precise correspondence has not been determined, 26 genes localized in HSA19q13.3-->q13.4 were assigned to the SSC6 region mainly by radiation hybrid (RH) mapping, and additionally, by somatic cell hybrid panel (SCHP) mapping, and fluorescent in situ hybridization (FISH). Out of the 26 genes, 24 were assigned to a swine RH map with LOD scores greater than 6 (threshold of significance). The most likely order of the 24 genes along SSC6 was calculated by CarthaGene, revealing that the order is essentially the same as that in HSA19q13.3-->q13.4. For AURKC and RPS5 giving LOD scores not greater than 6, SCHP mapping and FISH were additionally performed; SCHP mapping assigned AURKC and RPS5 to SSC6q22-->q23 and SSC6q21, respectively, which is consistent with the observation of FISH. Consequently, all the genes (26 genes) examined in the present study were shown to localize in SSC6q12-->q23, and the order of the genes along the chromosomes was shown to be essentially the same in swine and human, though several intrachromosomal rearrangements were observed between the species.

Animals↗
PubMed2005

Molecular cytogenetic characterization of ring chromosome 4 in a female having a chromosomally normal child.

We present the clinical and molecular findings of mosaic ring chromosome 4. The patient was referred to us for infertility and short stature. Results of three repeated cytogenetic analyses from lymphocytes showed a similar mosaic karyotype with multiple cell-lines [46,XX,r(4)/45,XX,-4/46,XX,dic r(4)/47,XX,r(4),+r(4)/46,XX]. FISH showed deletion of the 4p subtelomeric region and the 4q telomeric region from the ring chromosome 4. The breakpoints were mapped using molecular analysis. Parental karyotypes were normal. During the course of this study, the patient became pregnant without assisted reproductive technology. The result of amniocentesis performed at 16 weeks gestation showed a normal karyotype. Delivery was uncomplicated. This is the first report, to our knowledge, of the presence of ring chromosome 4 having various mosaic conditions in a female having a chromosomally normal fetus.

Adult↗
PubMed1977

Chromosome analysis in the Kruger National Park: the chromosomes of the bushbuck (Tragelaphus scriptus).

Chromosome studies in the male and female bushbuck (Tragelaphus scriptus) are discribed. The male has a diploid chromosome number of one fewer than the female, and the Y-to-autosome fusion. The configuration of a quadrivalent observed in meiotic preparations from the male confirmed the presence of a fusion between a Y chromosome and an autosome. All other members of the tragelaphine tribe so far studied chromosomally show the presence of a Y-to-autosome fusion. It is postulated that the fusion observed in all present-day species of the tribe studied to date arose as a single event in a common ancestor.

Animals↗
PubMed1980

Chromosomal assignment of the gene for folylpolyglutamate synthetase to human chromosome 9.

An auxotrophic mutant, GAT-, derived from the Chinese hamster cell line CHO-K1 and exhibiting multiple growth requirements for glycine, adenine, and thymidine, has been shown to be deficient in one of the folate-dependent enzymes, folylpolyglutamate synthetase (FPGS). This mutant was fused with normal human lymphocytes and human lymphoblasts and 41 GAT+ primary hybrid clones were isolated in medium lacking glycine, adenine, and thymidine. In addition, 71 secondary clones were isolated after growth of four primary hybrid clones in enriched medium, which allows losing the complementing human chromosome without losing cell viability. Analysis of human isozyme markers in the 112 primary and secondary clones established a syntenic relationship between the GAT marker and AK1, an isozyme marker for human chromosome 9. Enzyme studies of the parental and hybrid cells not only showed restored enzyme activities of FPGS in the hybrids, but also demonstrated that several enzyme characteristics of FPGS in the hybrids are consistent with those of the human enzyme. Thus, it is concluded that the human gene coding for the enzyme FPGS which complements the auxotrophic mutant GAT- in the CHO-K1 cells can be assigned to human chromosome 9. This assignment provides an additional selective marker for mammalian cell genetic analysis in which human chromosome 9 can be selectively and stably retained in the cell hybrids.

Animals↗
PubMed1985

The thyroglobulin gene resides on chromosome 8 in man and on chromosome 7 in the rat.

Human chromosomes were separated by a dual laser FACS sorter and their DNA hybridized with a thyroglobulin gene probe. A strong hybridization signal was obtained with DNA from chromosome 8. A panel of mouse-rat cell hybrids was used to determine the chromosomal localization of the rat thyroglobulin gene by the Southern blotting method. Comparison of the cytogenetic data with the hybridization signals obtained with the rat thyroglobulin probe allowed assignment of this gene to rat chromosome 7. It is concluded that the synteny relationship between the thyroglobulin gene and the c-myc oncogene has been conserved in rat and man.

Animals↗
PubMed1993

In humans all U3 genes map to chromosome 17p12-->p11, but in mouse the U3A and U3B genes are located on different chromosomes.

U3 small nucleolar RNA, which participates in eukaryotic rRNA processing, is encoded by a small multigene family in mammals. In humans, the four to six gene copies code for an identical U3 RNA molecule; rodents, however, have two variant forms of these genes, U3A and U3B. We show that all U3 genes in humans map to a single chromosomal locus, 17p12-->-p11, which corresponds exactly to the region of mouse Chromosome 11 where the four U3B genes are clustered. By contrast, in mouse the unique U3A gene copy is not linked to the U3B gene cluster but maps to another chromosome (the B2-B4 region of Chromosome 10).

Animals↗
PubMed1994

Seven genes on the short arm of human chromosome 3 map to two regions on Macropus eugenii (tammar wallaby) chromosome 2.

Seven genes were mapped by in situ hybridization to metaphase chromosomes of the marsupial species Macropus eugenii, using a series of human-derived cloned probes (six cosmids and one cDNA). The genes were located in two widely separated clusters on the long arm of M. eugenii chromosome 2, in contrast to their location in a single cluster on the distal half of the short arm of human chromosome 3. Multiple rearrangements had to be involved in the evolutionary divergence of these chromosome segments from the unknown arrangement in the common ancestor.

Animals↗
PubMed1995

Mapping of synapsin II (SYN2) genes to human chromosome 3p and mouse chromosome 6 band F.

Synapsins are neuron-specific phosphoproteins of small synaptic vesicles encoded by two different genes. While the gene for synapsin I (SYN1) is on the X chromosome, we have now assigned the human and mouse synapsin II (SYN2) genes to autosomes. By using PCR primers derived from rat synapsin II cDNA sequences we were able to amplify homologous sequences of the 3'-untranslated regions and to localize the human SYN2 gene to 3p and the mouse Syn2 gene to mouse chromosome 6 by single strand conformation analysis of PCR products from panels of somatic hybrid cell lines. The mouse gene was further mapped by FISH to chromosome 6 band F in a region of known conserved synteny with human 3p. Genotyping of a M. musculus x M. spretus backcross panel placed Syn2 close to a cluster of previously mapped loci on chromosome 6 in an interval between interleukin 5 receptor alpha (Il5ra) and hematopoietic cell phosphatase 1C (Hcph). Both physical and genetic mapping data indicate that Syn2 is near two mutant loci defined by neuromuscular disorders, opisthotonus (opt) and deaf waddler (dfw).

Animals↗
PubMed1997

Shared synteny between human chromosome 10 and chromosome 1 of the marsupial tammar wallaby, Macropus eugenii.

Marsupial homologs of the human chromosome 10 loci IL2RA, HK1, and PLAU have been cloned and mapped by fluorescence in situ hybridization to chromosome 1q of the tammar wallaby, Macropus eugenii. Relative distance measurements of the hybridization signals on M. eugenii chromosome 1 show that marsupial homologs of human (HSA) 10p IL2RA and 10q HK1/PLAU flank the marsupial homologs of the human 5q gene IL5 and the human 15q imprinted genes SNRPN and ZNF127. The shared synteny, therefore, does not necessarily mean that HSA 10 represents an ancestral grouping; rather, it suggests that HSA 10p and HSA 10q represent two different ancestral mammalian units which fused directly in primates and were incorporated independently into two different regions of the same chromosome in marsupials.

Animals↗
PubMed1997

Complex FISH probes for the subtelomeric regions of all human chromosomes: comparative hybridization of CEPH YACs to chromosomes of the Old World monkey Presbytis cristata and great apes.

We have generated a human subtelomere probe panel, utilizing well characterized CEPH YACs, for the investigation of human chromosome pathology and evolution through fluorescent in situ hybridization (FISH). Region-specific FISH probes will be extremely valuable for detecting cytogenetically cryptic telomere abnormalities. Here, we present the first comparative mapping study (with 29 subtelomere probes and 6 chromosome paints) to the Old World monkey Presbytis cristata, followed by hybridizations to the great apes, gorilla and orangutan, when rearrangements were detected. We observed that the position of telomere-associated genomic sequences has been only moderately conserved during primate evolution. YAC 364f9, specific for the subtelomeric long arm of human chromosome 3, contains an evolutionary inversion breakpoint that was involved in independent chromosome rearrangements in P. cristata and gorilla.

Animals↗
PubMed1985

Ph chromosome and B-cell malignancy-associated chromosomal aberrations in non-leukaemic immunoblastic B-cell lymphoma.

A 62-year-old female with a microK phenotypic immunoblastic B-cell lymphoma with bone marrow involvement but without leukaemia is reported. Bone marrow cells, cytogenetically studied at diagnosis, showed a Philadelphia chromosome due to a (9p;22q) translocation, deleted chromosomes 3 and 6, a 14q+ marker, and two extra chromosomes 18. The Ph chromosome is previously only once reported in a well-characterized B-cell lymphoma, whereas the latter aberrations are common findings in B-cell malignancies.

B-Lymphocytes↗
PubMed1995

Cryptorchidism and marker chromosomes: identification of marker chromosomes by fluorescence in situ hybridization.

Identification of marker chromosomes by fluorescence in situ hybridization was performed in 2 cases of cryptorchidism. In case 1, the marker chromosome was derived from chromosome 22. In case 2, the origin of the marker was the centromere of chromosome 8. The extent of the congenital anomalies in these cases was milder than that in cases with complete trisomy of an autosome. These findings suggest that an incomplete extra autosome might influence clinical characteristics.

Adolescent↗