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PubMed2003

Condensin-dependent localisation of topoisomerase II to an axial chromosomal structure is required for sister chromatid resolution during mitosis.

Assembly of compact mitotic chromosomes and resolution of sister chromatids are two essential processes for the correct segregation of the genome during mitosis. Condensin, a five-subunit protein complex, is thought to be required for chromosome condensation. However, recent genetic analysis suggests that condensin is only essential to resolve sister chromatids. To study further the function of condensin we have depleted DmSMC4, a subunit of the complex, from Drosophila S2 cells by dsRNA-mediated interference. Cells lacking DmSMC4 assemble short mitotic chromosomes with unresolved sister chromatids where Barren, a non-SMC subunit of the complex is unable to localise. Topoisomerase II, however, binds mitotic chromatin after depletion of DmSMC4 but it is no longer confined to a central axial structure and becomes diffusely distributed all over the chromatin. Furthermore, cell extracts from DmSMC4 dsRNA-treated cells show significantly reduced topoisomerase II-dependent DNA decatenation activity in vitro. Nevertheless, DmSMC4-depleted chromosomes have centromeres and kinetochores that are able to segregate, although sister chromatid arms form extensive chromatin bridges during anaphase. These chromatin bridges do not result from inappropriate maintenance of sister chromatid cohesion by DRAD21, a subunit of the cohesin complex. Moreover, depletion of DmSMC4 prevents premature sister chromatid separation, caused by removal of DRAD21, allowing cells to exit mitosis with chromatin bridges. Our results suggest that condensin is required so that an axial chromatid structure can be organised where topoisomerase II can effectively promote sister chromatid resolution.

Adenosine Triphosphatases↗
PubMed1978

Structural chromosome abnormalities in Down syndrome: a study of two families.

Two families were ascertained through a proband with Down syndrome and a structural rearrangement involving two chromosomes 21. It is suggested that in one patient the chromosome is an isochromosome formed by misdivision of the centromere of a maternal telocentric chromosome 21 and that in the other a Robertsonian translocation involving chromosome 21 was inherited from the mother, who is a 46,XX/46,XX, -21,+t(21q21q) mosaic. The origin of the mosaicism is discussed and considered to be likely to be the result of breakage and reunion at the chromatid, rather than the chromosome, level.

Adult↗
PubMed1993

Mammalian chromosome structure.

The DNA sequences that are necessary for the formation of a functional mammalian chromosome are thought to be the origins of replication, the telomeres and the centromere. Telomere structure is now well understood, with the functional element characterized as the motif (TTAGGG)n. The structures of the DNA regions that contain origins of replication and a centromere are known, but the functionally important elements within these regions are still only poorly defined.

Animals↗
PubMed1992

Primary structure, chromosomal localization, and functional expression of a voltage-gated sodium channel from human brain.

A cDNA library derived from human cerebral cortex was screened for the presence of sodium channel alpha subunit-specific clones. Ligation of three overlapping clones generated a full-length cDNA clone, HBA, that provided the complete nucleotide sequence coding for a protein of 2005 amino acids. The predicted structure suggests four homologous repeats and exhibits greatest homology and structural similarity to the rat brain sodium channel II. A second cDNA clone, HBB, that encodes a different subtype of sodium channel was isolated. Hybridization of DNA fragments from the 3' untranslated region of HBA and PCR with primers derived from HBB with human-hamster somatic cell hybrids localized these clones to human chromosome 2. In situ hybridization to human metaphase chromosomes mapped the structural genes for both HBA and HBB sodium channels to chromosome 2q23-24.3. The sodium channel HBA gene product was expressed by transfection in CHO cells. Expressed HBA currents were voltage-dependent, sodium-selective, and tetrodotoxin-sensitive and, thus, exhibit the biophysical and pharmacological properties characteristic of sodium channels.

Amino Acid Sequence↗
PubMed1973

Chromosome structure as revealed by a combined chemical and immunochemical procedure.

Human metaphase chromosomes were photooxidized in the presence of methylene blue, a process that destroys guanine residues in DNA. Indirect immunofluorescence showed that such chromosomes reacted with a cytosine-specific antibody revealing a consistent fluorescent banding pattern by which each chromosome could be identified. The observed fluorescent patterns were the reverse of those produced in formamide-denatured chromosomes treated with an antibody specific for adenine and of the patterns obtained with quinacrine and with Giemsa staining by the G-banding techniques. The patterns were identical to Giemsa R-banding patterns. The chromosome banding patterns, therefore, appeared to reflect DNA base composition, indicating the feasibility of a combined chemical-immunochemical investigation of the chemical organization of chromosomes.

Antibodies, Antinuclear↗
PubMed1976

Chromosome structure in Chilocorus (Coleoptera: Coccinellidae). II. The asynchronous replication of constitutive heterochromatin.

Chromosome replication has been analysed in four species of Chilocorus. In C. ORBUS Csy., C. tricyclus Smith, and C. hexacyclus Smith, centric regions of all chromosomes are last to replicate, preceded in order by heterochromatic arms and euchromatic arms. In C. stigma Say, very late replication of centric regions can be detected only in otherwise wholly euchromatic chromosomes (= monophasics); in chromosomes with one arm heterochromatic ( = disphasics), these arms are last to replicate. Based on pachytene bivalent morphology and chromosome banding patterns, and supported by autoradiographic data, models are presented for the general organisation of Chilocorus chromosomes. All chromosomes in the first three species are subdivided into euchromatic arm, centric heterochromatin, and either a second euchromatic are (monophasics) or a heterochromatic arm (diphasics). Chilocorus stigma diphasics apparently lack distinct centric organisation, and are therefore divided into euchromatic and heterochromatic arms only.

Animals↗
PubMed2001

Structure, chromosomal location, and tissue-specific expression of the mouse opticin gene.

PURPOSE: To determine the structure, location, and tissue-specific expression of the mouse opticin gene (Optc) and to compare expression in the eye with that of Prelp, collagen II, and collagen IX. METHODS: Expressed sequence tags (ESTs) to mouse opticin were identified and the full-length sequence obtained after PCR reactions using a 15-day-postconception (dpc) whole-mouse embryo cDNA library. The mouse chromosomal localization of Optc was determined by radiation hybrid mapping and its genomic structure determined using an Optc-containing BAC clone. Tissue-specific expression of opticin, PRELP, collagen II, and collagen IX mRNAs was investigated by in situ hybridization and by dot blot hybridization for opticin. RESULTS: The Optc gene was localized to mouse chromosome 1 at 74.3 cM and consisted of seven exons spanning 10 kb. The Optc gene was less than 4 kb from the Prelp gene. In situ hybridization localized opticin mRNA exclusively to the presumptive ciliary body during development and to the nonpigmented ciliary epithelium of the adult mouse eye. Expression of Prelp was also detected in the nonpigmented ciliary epithelium of the adult eye. However, expression of collagen types II and IX was detected largely in the developing mouse eye, with type IX expression confined primarily to the presumptive ciliary body. CONCLUSIONS: The Optc, Prelp, and fibromodulin (Fmod) genes form a cluster on mouse chromosome 1. Opticin may represent a marker for ciliary body differentiation. Continued expression of opticin in the adult mouse eye suggests functions other than that of putative regulator of vitreous collagen fibrillogenesis.

Amino Acid Sequence↗
PubMed1991

Chromosome structure and eukaryotic gene organization.

The DNA in the eukaryotic nucleus is highly compacted but well organized into distinct regional units. Chromosomal bands are characterized by their structure and distinctive replication time. They are subdivided into chromatin loops which serve as functional domains that have discrete boundary elements and can be regulated during development.

Animals↗
PubMed2005

Insights from genomic microarrays into structural chromosome rearrangements.

Array-based comparative genomic hybridization allows high-resolution screening of copy number abnormalities in the genome, and becomes an increasingly important tool to detect deletions and duplications in tumor and post-natal cytogenetics. Here we illustrate that genomic arrays can also provide novel clues regarding the structural basis of chromosome rearrangement, including instability and mechanisms of formation of ring chromosomes. We also showed that array results might impact the recurrence risks for relatives of affected individuals. Our data indicate that chromosome rearrangements frequently involve more breaks than current cytogenetic models assume.

Cell Line↗
PubMed2000

DNA in situ hybridization (interphase cytogenetics) versus comparative genomic hybridization (CGH) in human cancer: detection of numerical and structural chromosome aberrations.

DNA in situ hybridization techniques for cytogenetic analyses of human solid cancers are nowadays widely used for diagnostic and research purposes. The advantage of this methodology is that it can be applied to cells in the interphase state, thereby circumventing the need for high-quality metaphase preparations for karyotypic evaluation. In situ hybridization (ISH) with chromosome specific (peri)centromeric DNA probes, also termed "interphase cytogenetics", can be used to detect numerical changes, whereas comparative genomic hybridization (CGH) discloses chromosomal gains and losses, i.e. amplifications and deletions. We wanted to compare both methods in human solid tumors, and for this goal we evaluated ISH and CGH within a set of 20 selected prostatic adenocarcinomas. Chromosomes 7 and 8 were chosen for this analysis, since these chromosomes are frequently altered in prostate cancer. ISH with chromosome 7 and 8 specific centromeric DNA probes was applied to standard, formalin-fixed and paraffin-embedded, histological sections for numerical chromosome analysis. CGH with DNA's, extracted from the same histologic area of the archival specimens, was used for screening of gains and losses of 7 and 8. ISH with centromeric probes distinguished a total of 26 numerical aberrations of chromosome 7 and/or 8 in the set of 20 neoplasms. In the same set CGH revealed a total of 35 losses and gains. CGH alterations of 7 and 8 were seen in twenty-two of the 26 chromosomes (85%) that showed aberrations in the ISH analysis. Concordance between ISH and CGH was seen in 11 (of 26; 42%) chromosomes. Eight chromosomes were involved in gains (5 x #7, 3 x #8), three in losses (3 x #8). This included both complete (3/11) and partial (8/11) CGH confirmation of the numerical alteration. Partial CGH confirmation was defined as loss or gain of a chromosome arm with involvement of the centromeric region. In the majority of these cases it concerned a whole chromosome arm, mostly the long arm. We conclude that generally a fair correlation was found between ISH and CGH in interphase preparations of a series of prostate cancers. However, when specified in detail, most of the numerical ISH aberrations were only partly represented in the CGH analysis. On the one hand, it suggests that CGH does not adequately discriminate numerical abnormalities. On the other hand, it likely implies that not all numerical changes, as detected by interphase cytogenetics, are truly involving the whole chromosome. A part of these discrepancies might be caused by structural mechanisms, most notably isochromosome formation.

Adenocarcinoma↗
PubMed1999

Characterization of the human talin (TLN) gene: genomic structure, chromosomal localization, and expression pattern.

Talin is a high-molecular-weight cytoskeletal protein, localized at cell-extracellular matrix associations known as focal contacts. In these regions, talin is thought to link integrin receptors to the actin cytoskeleton. Talin plays a key role in the assembly of actin filaments and in spreading and migration of various cell types. Talin proteins are found in a wide variety of organisms, from slime molds to humans. The human Talin (HGMW-approved symbol TLN) gene was previously mapped to chromosome 9p, but little was known of its sequence and genomic structure. To characterize human TLN further, we have isolated a single bacterial artificial chromosome clone, harboring the entire gene. The gene extends over more than 23 kb and consists of 57 exons. We have localized TLN to human chromosome band 9p13 by both fluorescence in situ hybridization and radiation hybrid mapping. Northern blot analysis detected TLN expression in various human tissues, including leukocytes, lung, placenta, liver, kidney, spleen, thymus, colon, skeletal muscle, and heart. Based on its chromosomal location, expression pattern, and protein function, we considered TLN as a candidate gene for cartilage-hair hypoplasia (CHH), an autosomal recessive metaphyseal chondrodysplasia, previously mapped to 9p13. We sequenced the entire TLN coding sequence in several CHH patients, but no functional mutations were detected.

Cartilage↗