Definition and refinement of chromosome 8p regions of loss of heterozygosity in gastric cancer.
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Loss of heterozygosity at several chromosomal loci is a common feature of the malignant progression of human tumors. These regions are thought to harbor one or more putative tumor suppressor gene(s) playing a role in tumor development. Allelic losses on the short arm of chromosome 8 (8p) have been reported as frequent events in several cancers, and three commonly deleted regions have been defined at 8p11.2-12, 8p21-22, and 8p23.1. To evaluate the possible involvement of these regions in gastric cancer, we used eight microsatellite markers to perform an extensive analysis of allele loss at 8p21-22 in 52 cases of primary gastric adenocarcinoma. We found that 44% of tumors showed allelic loss for at least one marker at 8p21-22. The critical region of loss was found to be between markers LPL and D8S258, which displayed loss of heterozygosity in 39% and 33% of cases, respectively. This region is centromeric to the LPL locus and centered on the D8S258 locus. We conclude that 8p22 deletion is a frequent event in gastric cancer and suggest the presence of a putative tumor suppressor gene near the D8S258 locus. Initial steps were taken toward the identification of this gene, which is likely to play an important role in the pathogenesis of gastric cancer and of other tumors as well. (+info)
Nijmegen breakage syndrome. The International Nijmegen Breakage Syndrome Study Group.
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BACKGROUND: Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder. NBS-1, the gene defective in NBS, is located on chromosome 8q21 and has recently been cloned. The gene product, nibrin, is a novel protein, which is member of the hMre11/hRad50 protein complex, suggesting that the gene is involved in DNA double strand break repair. AIMS: To study the clinical and laboratory features of NBS as well as the genotype-phenotype relation. METHODS: Fifty five patients with NBS, included in the NBS registry in Nijmegen were evaluated. The majority of the patients were of eastern European ancestry. Most of them had shown a truncating 5 bp deletion 657-661 delACAAA. Four further truncating mutations have been identified in patients with other distinct haplotypes. RESULTS AND CONCLUSIONS: Essential features found in NBS were microcephaly, usually without severe retardation, typical facial appearance, immunodeficiency, chromosomal instability, x ray hypersensitivity, and predisposition to malignancy. In 40% of the patients cancer was noted before the age of 21 years. Important additional features were skin abnormalities, particularly cafe au lait spots and vitiligo, and congenital malformations, particularly clinodactyly and syndactyly. Congenital malformations, immunodeficiency, radiation hypersensitivity, and cancer predisposition were comprehensible in case of dysfunctioning of DNA repair mechanisms. No specific genotype-phenotype relation could be found. Patients with the same genotype may show different phenotypes and patients with different genotypes may express the same phenotype. Specific mutations did not lead to specific clinical features. (+info)
Chromosome 8p alterations in sporadic and BRCA2 999del5 linked breast cancer.
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Chromosomal losses involving the short arm of chromosome 8 are frequent in a variety of tumour types, including breast cancer, suggesting the presence of one or more tumour suppressor genes in this region. In this study, we have used 11 microsatellite markers to analyse loss of heterozygosity (LOH) at chromosome 8p in 151 sporadic breast tumours and 50 tumours from subjects carrying the BRCA2 999del5 mutation. Fifty percent of sporadic tumours compared to 78% of BRCA2 linked tumours exhibit LOH at one or more markers at 8p showing that chromosome 8p alterations in breast tumours from BRCA2 999del5 carriers are more pronounced than in sporadic breast tumours. The pattern of LOH is different in the two groups and a higher proportion of BRCA2 tumours have LOH in a large region of chromosome 8p. In the total patient material, LOH of 8p is associated with LOH at other chromosome regions, for example, 1p, 3p, 6q, 7q, 9p, 11p, 13q, 17p, and 20q, but no association is found between LOH at 8p and chromosome regions 11q, 16q, 17q, and 18q. Furthermore, an association is detected between LOH at 8p and positive node status, large tumour size, aneuploidy, and high S phase fraction. Breast cancer patients with LOH at chromosome 8p have a worse prognosis than patients without this defect. Multivariate analysis suggests that LOH at 8p is an independent prognostic factor. We conclude that chromosome 8p carries a tumour suppressor gene or genes, the loss of which results in growth advantage of breast tumour cells, especially in carriers of the BRCA2 999del5 mutation. (+info)
Identification and characterization of a new human ETS-family transcription factor, TEL2, that is expressed in hematopoietic tissues and can associate with TEL1/ETV6.
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The ETS family of proteins is a large group of transcription factors implicated in many aspects of normal hematopoietic development, as well as oncogenesis. For example, the TEL1/ETV6 (TEL1) gene is required for normal yolk sac angiogenesis, adult bone marrow hematopoiesis, and is rearranged or deleted in numerous leukemias. This report describes the cloning and characterization of a novel ETS gene that is highly related to TEL1 and is therefore called TEL2. The TEL2 gene consists of 8 exons spanning approximately 21 kilobases (kb) in human chromosome 6p21. Unlike the ubiquitously expressed TEL1 gene, however, TEL2 appears to be expressed predominantly in hematopoietic tissues. Antibodies raised against the C-terminus of the TEL2 protein were used to show that TEL2 localizes to the nucleus. All ETS proteins can bind DNA via the highly conserved ETS domain, which recognizes a purine-rich DNA sequence with a GGAA core motif. DNA binding assays show that TEL2 can bind the same consensus DNA binding sequence recognized by TEL1/ETV6. Additionally, the TEL2 protein is capable of associating with itself and with TEL1 in doubly transfected Hela cells, and this interaction is mediated through the pointed (PNT) domain of TEL1. The striking similarities of TEL2 to the oncogenic TEL1, its expression in hematopoietic tissues, and its ability to associate with TEL1 suggest that TEL2 may be an important hematopoietic regulatory protein. (+info)
N-myc downstream-regulated gene 1 is mutated in hereditary motor and sensory neuropathy-Lom.
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Hereditary motor and sensory neuropathies, to which Charcot-Marie-Tooth (CMT) disease belongs, are a common cause of disability in adulthood. Growing awareness that axonal loss, rather than demyelination per se, is responsible for the neurological deficit in demyelinating CMT disease has focused research on the mechanisms of early development, cell differentiation, and cell-cell interactions in the peripheral nervous system. Autosomal recessive peripheral neuropathies are relatively rare but are clinically more severe than autosomal dominant forms of CMT, and understanding their molecular basis may provide a new perspective on these mechanisms. Here we report the identification of the gene responsible for hereditary motor and sensory neuropathy-Lom (HMSNL). HMSNL shows features of Schwann-cell dysfunction and a concomitant early axonal involvement, suggesting that impaired axon-glia interactions play a major role in its pathogenesis. The gene was previously mapped to 8q24.3, where conserved disease haplotypes suggested genetic homogeneity and a single founder mutation. We have reduced the HMSNL interval to 200 kb and have characterized it by means of large-scale genomic sequencing. Sequence analysis of two genes located in the critical region identified the founder HMSNL mutation: a premature-termination codon at position 148 of the N-myc downstream-regulated gene 1 (NDRG1). NDRG1 is ubiquitously expressed and has been proposed to play a role in growth arrest and cell differentiation, possibly as a signaling protein shuttling between the cytoplasm and the nucleus. We have studied expression in peripheral nerve and have detected particularly high levels in the Schwann cell. Taken together, these findings point to NDRG1 having a role in the peripheral nervous system, possibly in the Schwann-cell signaling necessary for axonal survival. (+info)
Positional cloning and functional analysis of the gene responsible for Nijmegen breakage syndrome, NBS1.
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Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder characterized by microcephaly, combined immunodeficiency, and a high incidence of lymphoid tumor. Cells from NBS patients show chromosomal instability, hypersensitivity to ionizing radiation and abnormal p53-mediated cell cycle regulation. We cloned the underlying gene for NBS, designated NBS1, by complementation-assisted positional cloning from the candidate region 8q21. Large genomic sequencing, as well as a search using computer programs, provides a powerful approach for identifying the underlying gene for a disease. The NBS1 gene encodes a protein of 754 amino acids that has FHA and BRCT domains which often are conserved in cell-cycle checkpoint proteins. The gene has weak homology to the yeast (Saccharomyces cerevisiae) Xrs2 protein in the N-terminus region. Like yeast Xrs2, the NBS1 protein forms a complex with hRAD50/hMRE11, and the complex is condensed as foci in the nucleus after irradiation, indicative that this triple-complex is a crucial factor in DNA repair. Functional analysis of the NBS1 protein is in progress and it should provide further clues to understanding the repair mechanism of radiation-induced DNA double-strand breaks. (+info)
A new variant of Charcot-Marie-Tooth disease type 2 is probably the result of a mutation in the neurofilament-light gene.
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Charcot-Marie-Tooth (CMT) disease is the most common inherited motor and sensory neuropathy. The axonal form of the disease is designated as "CMT type 2" (CMT2). Although four loci known to be implicated in autosomal dominant CMT2 have been mapped thus far (on 1p35-p36, 3q13. 1, 3q13-q22, and 7p14), no one causative gene is yet known. A large Russian family with CMT2 was found in the Mordovian Republic (Russia). Affected members had the typical CMT2 phenotype. Additionally, several patients suffered from hyperkeratosis, although the association, if any, between the two disorders is not clear. Linkage with the CMT loci already known (CMT1A, CMT1B, CMT2A, CMT2B, CMT2D, and a number of other CMT-related loci) was excluded. Genomewide screening pinpointed the disease locus in this family to chromosome 8p21, within a 16-cM interval between markers D8S136 and D8S1769. A maximum two-point LOD score of 5.93 was yielded by a microsatellite from the 5' region of the neurofilament-light gene (NF-L). Neurofilament proteins play an important role in axonal structure and are implicated in several neuronal disorders. Screening of affected family members for mutations in the NF-L gene and in the tightly linked neurofilament-medium gene (NF-M) revealed the only DNA alteration linked with the disease: a A998C transversion in the first exon of NF-L, which converts a conserved Gln333 amino acid to proline. This alteration was not found in 180 normal chromosomes. Twenty unrelated CMT2 patients, as well as 26 others with an undetermined form of CMT, also were screened for mutations in NF-L, but no additional mutations were found. It is suggested that Gln333Pro represents a rare disease-causing mutation, which results in the CMT2 phenotype. (+info)
Narrowing the Duane syndrome critical region at chromosome 8q13 down to 40 kb.
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Duane syndrome (MIM 126800) is an autosomal dominant disorder characterised by primary strabismus and other ocular anomalies, associated with variable deficiency of binocular sight. We have recently identified a < 3 cM smallest region of deletion overlap (SRO) by comparing interstitial deletions at band 8q13 in two patients (one described by Vincent et al, 1994, and the other by Calabrese et al, 1998). Here we report on another patient with Duane syndrome carrying a reciprocal translation t(6;8)(q26;q13). FISH and PCR analyses using a YAC contig spanning the SRO narrowed the Duane region to a < 1 cM interval between markers SHGC37325 and W14901. In addition, the identification and mapping of two PAC clones flanking the translocation breakpoint, allowed us to further narrow the critical region to about 40 kb. As part of these mapping studies, we have also refined the map position of AMYB, a putative candidate gene, to 8q13, centromeric to Duane locus. AMYB is expressed in brain cortex and genital crests and has been previously mapped to 8q22. (+info)