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Biomedical subjects

I Vorechovsky

Publications and source records attributed to I Vorechovsky.

At least 19 recordsLinked to original sources
PubMed2002

The HLA-DRA*0102 allele: correct nucleotide sequence and associated HLA haplotypes.

Here we correct the nucleotide sequence of a single known variant of the HLA-DRA gene. We show that the coding regions of the HLA-DRA*0101 and HLA-DRA*0102 alleles do not differ at two codons as reported previously, but only in codon 217. Using nucleotide sequencing and DNA samples from individuals homozygous in the major histocompatibility complex, we found that the variant, leucine 217-encoding HLA-DRA*0102 allele was present on the haplotypes HLA-B*0801, DRB1*03011, DQB1*0201 (ancestral haplotype AH8.1), HLA-B*07021, DRB1*15011, DQB1*0602 (AH7.1), HLA-B*1501, DRB1*15011, DQB1*0602, HLA-B*1501, DRB1*1402, DQB1*03011 and HLA-A3, B*07021, DRB1*1301, DQB1*0603. The HLA-DRA*0101 allele coding for valine 217 was observed on the haplotypes HLA-B*5701, DRB1*0701, DQB1*03032 (AH57.1), HLA-DRB1*04011, DQB1*0302, HLA-DRB1*0701, DQB1*0202, and HLA-DRB1*0101, DQB1*05011.

Alleles↗
PubMed2001

Low frequency of E-cadherin alterations in familial breast cancer.

In order to explore the possible role of E-cadherin in familial cancer, 19 familial breast cancer patients, whose tumours demonstrated loss of heterozygosity (LOH) at the E-cadherin locus, were screened for germline mutations. No pathogenic germline alterations were detected in these individuals. However, a somatic mutation was found (49-2A-->C) in one of the tumours. This tumour showed a pattern of both ductal and lobular histology. Another 10 families with cases of breast, gastric and colon cancer were also screened for germline mutations, and no mutations were found. A missense mutation in exon 12 of E-cadherin (1774G-->A; Ala592Thr) was previously found in one family with diffuse gastric cancer, and colon and breast cancer. An allelic association study was performed to determine whether the Ala592Thr alteration predisposes to breast cancer. In total, we studied 484 familial breast cancer patients, 614 sporadic breast cancer patients and 497 control individuals. The frequencies of this alteration were similar in these groups. However, a correlation between the Ala592Thr alteration and ductal comedo-type tumour was seen. These results, together with previously reported studies, indicate that germline mutations and, more commonly, somatic mutations in E-cadherin may have an influence on the behaviour of the tumours, rather than predispose to breast cancer.

Adult↗
PubMed2001

Does 77C-->G in PTPRC modify autoimmune disorders linked to the major histocompatibility locus?

A 77G allele of the gene encoding CD45, also known as the protein tyrosine phosphatase receptor-type C gene (PTPRC), has been associated with multiple sclerosis (MS). Here we determine allele frequencies in large numbers of MS patients, primary immunodeficiencies linked to major histocompatibility complex (MHC) locus and over 1,000 controls to assess whether aberrant splicing of PTPRC caused by the 77C-->G polymorphism results in increased susceptibility to these diseases. Our results show no difference in the frequency of the 77G allele in patients and controls and thus do not support a causative role for the polymorphism in the development of disorders with a strong autoimmune component in etiology.

Animals↗
PubMed2001

Short tandem repeat (STR) haplotypes in HLA: an integrated 50-kb STR/linkage disequilibrium/gene map between the RING3 and HLA-B genes and identification of STR haplotype diversification in the class III region.

We present a dense STR/linkage disequilibrium(LD)/gene map between the RING3 and HLA-B loci, reference allelic sizes on the most prevalent HLA haplotypes and their allelic frequencies in pedigree founders. This resource will facilitate LD, evolution and gene mapping studies, including comparisons of HLA and STR haplotypes and identification of HLA recombinants. The map was constructed by testing novel and previously reported STRs using a panel of 885 individuals in 211 families and 60 DNA samples from cell lines and bone marrow donors homozygous in the HLA-A, -B and -DR loci selected from over 15 000 entries into the registry of Swedish bone marrow donors. We have also analysed the variability of STR alleles/haplotypes on the most prevalent HLA haplotypes to identify STRs useful for fine mapping of disease genes in the region previously implicated in susceptibility to many disorders. The analysis of 40 HLA-A*01, B*0801, DRB1*03011, DQB1*0201 haplotypes in homozygous donors showed a surprising stability in 23 STRs between the class II recombination hot spot and HLA-B, with the average of 1.9% (16/838) variant alleles. However, 40% variant alleles were found at the D6S2670 locus in intron 19 of the tenascin-X gene both in the families and homozygous donors. The nucleotide sequence analysis of this STR showed a complex polymorphism consisting of tetra- (CTTT)(8-18) and penta-nucleotide (CTTTT)(1-2) repeats, separated by an intervening non-polymorphic sequence of 42 bp. The HLA-A1, B*0801, DRB1*03011, DQB1*0201 haplotypes had five (CTTT)(14-18)/(CTTTT)(2) variants with a predominant (CTTT)(16) allele, implicating the tetranucleotide component as the source of this ancestral haplotype diversification, which may be due to the location of D6S2670 in the region of the highest GC content in the human MHC.

Centromere↗
PubMed2001

Allelic imbalance on chromosomes 13 and 17 and mutation analysis of BRCA1 and BRCA2 genes in monozygotic twins concordant for breast cancer.

To study genetic changes associated with the development of breast cancer and the extent of its hereditary predisposition, paraffin-embedded tissue samples were obtained from monozygotic twin pairs concordant for breast cancer through the linked Swedish Twin and Cancer Registries. DNA samples extracted from the matched tumour and normal tissues of nine twin pairs were analysed for allelic imbalance using a series of microsatellite markers on chromosomes 13 and 17, containing loci with known tumour suppressor genes. Multiple losses of constitutional heterozygosity (LOH), consistent with a loss of large genomic region, the whole chromosome or chromosome arm, was found in at least three pairs of twins. One double mitotic crossover was identified in one tumour sample in a pair concordant for LOH at multiple loci on both chromosomes. Recombination breakpoints were mapped to regions delineated by D13S218 and D13S263, and D13S155 and D13S279, respectively. In general, no genetic effect of losing the same allele within a twin pair was found. However, for one marker at chromosome 13 (D13S328, between the BRCA2 and the RB-1 loci) and two markers on chromosome 17 (D17S786, distal to the p53 locus, and D17S855, an intragenic BRCA1 marker) the proportion of twin pairs with the same LOH was significantly higher than expected. These regions may reflect hereditary genomic changes in our sample set. In addition, tumour DNA samples from a subset of 12 twin pairs were analysed for BRCA1 and BRCA2 mutations using exon-by-exon single-strand conformation polymorphism analysis. Two unclassified BRCA2 variants, with a putative pathogenic effect, were identified, but no pathogenic alterations were found in the BRCA1 gene.

Adult↗
PubMed2000

Low frequency of alterations of the alpha (PPP2R1A) and beta (PPP2R1B) isoforms of the subunit A of the serine-threonine phosphatase 2A in human neoplasms.

The phosphatase 2A (PP2A) is one of the major cellular serine-threonine phosphatases. It was recently shown that the gene encoding for the beta isoform of its subunit A, PPP2R1B, is altered in human lung and colorectal carcinomas, suggesting a role in human tumorigenesis. Here, we report the detection of mutations in breast, lung carcinomas and melanomas in the genes of both alpha (PPP2R1A) and beta isoforms. Mutations affecting PPP2R1B were found in four breast carcinomas, while mutations in PPP2R1A were found in carcinomas of the breast and of the lung and in one melanoma. Most of the mutations affecting PPP2R1B were exons deletions, suggesting abnormal splicing. These splicing abnormalities were detected in tumor samples in the absence of the normal splicing product, and were not found in several normal controls. In one case, a homozygous deletion present in tumor DNA, and not in the matched normal control was demonstrated. Mutations affecting the PPP2R1A gene were nucleotide substitutions changing highly conserved amino acids and one frame-shift. Although the frequency of alterations is low, the inclusion of both isoforms of subunit A in the genes mutated in human cancer and the addition of breast cancer to the list of neoplasms in which PPP2R1B is altered, strengthen the potential role of PP2A in human tumorogenesis.

Amino Acid Substitution↗
PubMed2000

UV mutation signature in tumor suppressor genes involved in skin carcinogenesis in xeroderma pigmentosum patients.

Molecular analysis of p53 and patched (PTCH), two candidate tumor suppressor genes for non-melanocytic skin cancer, was performed in skin tumors from six patients affected by the cancer-prone disease xeroderma pigmentosum (XP). UV-specific p53 mutations were detected at a frequency of 38-50% in all the tumor types analysed, including melanomas. Additional analysis of PTCH mutations in the subset of eight basal call carcinomas (BCC) revealed a very high mutation frequency of this gene (90%) which exceeded that detected in the p53 gene in the same tumors (38%). PTCH mutations were predominantly UV-specific C>T transitions. This mutation pattern is different from that reported in BCC from normal donors where PTCH mutation frequency is 27% and mutations are frequently deletions and insertions. These findings suggest that PTCH mutations represent an earlier event in BCC development than p53 alterations and that the inability of XP patients to repair UV-induced PTCH mutations might significantly contribute to the early and frequent appearance of BCC observed in these patients.

Adult↗
PubMed1999

Refinement of the LOH region 1 at 11q23.1 deleted in human breast carcinomas and sublocalization of 11 expressed sequence tags within the refined region.

Loss of constitutive heterozygosity at 11q23 has been detected in various human solid tumors. Here, we described the analysis of a series of normal and tumor pairs from 110 breast carcinomas for the presence of loss of heterozygosity at 11q23 loci. The overall frequency of LOH was 48%, confirming the importance of deletions at 11q23 in breast tumorigenesis. Previously, we have identified two independent regions of LOH at 11q23, the LOH region 1 at 11q23.1 and the LOH region 2 at 11q23.3. The most telomeric region was recently refined between loci D11S1345 and D11S1316, a region of about 1 Mb. However, the LOH region 1, most centromeric, was still not finely refined: the boundaries were defined by loci D11S2000 and D11S897, separated by about 8 Mb. Here, we refined its boundaries between loci D11S1347 and D11S927, a region of about 2 Mb. We have mapped 11 expressed sequence tags (ESTs) within this region and excluded another 20. This study represents a further step toward the identification of the putative tumor suppressor gene found within the LOH region 1 at 11q23.1.

Breast Neoplasms↗
PubMed1998

Molecular cloning and characterization of ZNF202: a new gene at 11q23.3 encoding testis-specific zinc finger proteins.

Two distinct regions of loss of heterozygosity (LOH) in breast carcinomas were previously identified at chromosome 11q23. With the aim of identifying a tumor suppressor gene, we undertook the isolation and characterization of genes within LOH region 2, defined between loci D11S1345 and D11S1316, which spans an area of about 1 Mb. Here, we describe the cloning and characterization of a new gene, ZNF202. The gene, which spans a genomic area of approximately 10 kb, is almost exclusively expressed in testis as a 4-kb mRNA. The predicted amino acid sequence of the protein product revealed significant homologies with zinc finger proteins, indicating that the ANF202 protein may function as a transcription factor. The presence of multiple CK2 and PKC phosphorylation sites suggests that its activity may be regulated by phosphorylation. The gene is also expressed in breast carcinoma cell lines. However, mutation analysis of 39 breast cancer samples revealed no evidence of mutations, indicating that ZNF202 is unlikely to be involved in the pathogenesis of this neoplasm. Nevertheless, a role for ZNF202 in the tumorigenic process of other tissues cannot be excluded.

Amino Acid Sequence↗
PubMed1997

Molecular cloning and characterization of LOH11CR2A, a new gene within a refined minimal region of LOH at 11q23.

Deletions at chromosome 11q23 are frequent events in a variety of human neoplasms, including breast, lung, and ovarian carcinomas. Two common regions of loss of heterozygosity, shared between lung and breast carcinomas, have been previously identified at 11q23, suggesting that the same tumor susceptibility genes are altered in these two malignancies. One of these regions, refined in lung adenocarcinoma, is included between loci D11S1345 and D11S1328. Here, we describe the refinement of the same region in breast carcinomas and the characterization of a new gene found within this area. The gene, called LOH11CR2A, spans an area of approximately 40 kb and is transcribed at a low level in all the tissues in which it has been analyzed. The predicted amino acid primary sequence revealed no homology with other proteins that could help to elucidate a possible function for the LOH11CR2A protein. Here, we tested the hypothesis that LOH11CR2A could be a tumor suppressor gene. Analysis of human breast, lung, and ovarian carcinomas revealed the presence of several amino acid substitutions in the coding region of this gene. However, a role for these amino acid changes in the tumorigenic process could not established.

Amino Acid Sequence↗
PubMed1997

BTKbase, mutation database for X-linked agammaglobulinemia (XLA)

X-linked agammaglobulinemia (XLA) is an immunodeficiency caused by mutations in the gene coding for Bruton's agammaglobulinemia tyrosine kinase (BTK). A database (BTKbase) of BTK mutations has been compiled and the recent update lists 368 entries from 318 unrelated families showing 228 unique molecular events. In addition to mutations the database lists also some polymorphisms and site-directed mutations. Each patient is given a unique patient identity number (PIN). Information is provided regarding the phenotype including symptoms. Mutations in all the five domains of BTK have been noticed to cause the disease, the most common event being missense mutations. The mutations appear almost uniformly throughout the molecule and frequently affect CpG sites forming arginine residues. These hot spots have generally pyrimidines 5'and purines 3'to the mutated cytosine. A decreased frequency of missense mutations was found in the TH, SH3 and the upper lobe of the kinase domain. The putative structural implications of all the missense mutations are given in the database showing 228 unique molecular events, including a novel missense mutation causing an R28C substitution as previously seen in the Xid mouse.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1996

Mutations in the human homologue of Drosophila patched (PTCH) in basal cell carcinomas and the Gorlin syndrome: different in vivo mechanisms of PTCH inactivation.

The nevoid basal cell carcinoma (Gorlin) syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple developmental defects and cancer susceptibility, in particular to basal cell carcinoma. The human homologue of Drosophila patched (PTCH) was recently identified, mapped to the NBCCS locus on chromosome 9q22.3, and found mutated in patients with NBCCS and also in sporadic basal cell carcinomas. Here we show germ-line PTCH mutations in three families with NBCCS. We demonstrate that a germ-line PTCH frameshift deletion in one patient with NBCCS was accompanied by loss of the normal copy of PTCH in a tumor developed in the same patient. Another basal cell carcinoma from this patient did not show the loss of the normal copy of PTCH, instead a missense mutation in a highly conserved residue was identified in the nondeleted allele, illustrating two different mechanisms of PTCH inactivation in different tumors derived from the same NBCCS patient. We also show somatic PTCH mutations in 4 basal cell carcinomas identified by analyzing 18 non-NBCCS patients with sporadic tumors. These data provide further support for PTCH as an important tumor suppressor gene in the development of the most common human cancer.

Adult↗
PubMed1996

The FHIT gene at 3p14.2 is abnormal in breast carcinomas.

Chromosome 3p deletions in breast cancer have been detected at 3p12-p21 by cytogenetic and loss of heterozygosity studies. Recently, we have cloned the FHIT (fragile histidine triad) gene, located at 3p14.2. Abnormalities of the FHIT locus were found in many established cancer cell lines, and the gene was abnormally transcribed in primary tumors of the digestive tract and lung. In this report, we describe the analysis of breast cancer, cell lines, and primary tumors for alterations in transcription of the FHIT gene; about 20% of the samples exhibited altered transcripts. In most of the cases, aberrant transcripts were missing exons. Lack of expression of FHIT mRNA was observed in another 10% of primary tumor samples. These results suggest that alterations in the FHIT gene may play an important role in breast cancer tumorigenesis and suggest that the MIT gene product functions in the control of the tumorigenic phenotype in a large variety of human neoplasms.

Acid Anhydride Hydrolases↗
PubMed1996

Mutations of the human homolog of Drosophila patched in the nevoid basal cell carcinoma syndrome.

The nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple basal cell carcinomas (BCCs), pits of the palms and soles, jaw keratocysts, a variety of other tumors, and developmental abnormalities. NBCCS maps to chromosome 9q22.3. Familial and sporadic BCCs display loss of heterozygosity in this region, consistent with the gene being a tumor suppressor. A human sequence (PTC) with strong homology to the Drosophila segment polarity gene, patched, was isolated from a YAC and cosmid contig of the NBCCS region. Mutation analysis revealed alterations of PTC in NBCCS patients and in related tumors. We propose that a reduction in expression of the patched gene can lead to the developmental abnormalities observed in the syndrome and that complete loss of patched function contributes to transformation of certain cell types.

Alleles↗