Biomedical subjects

C E Yu

Publications and source records attributed to C E Yu.

At least 19 recordsLinked to original sources

PubMed2000

The Werner syndrome protein contributes to induction of p53 by DNA damage.

Mutations in the p53 tumor-suppressor gene promote increased genomic instability and cancer. Mutations in the WRN gene, encoding a DNA helicase, underlie the segmental progeroid Werner syndrome (WS). WS is also associated with increased genomic instability and elevated cancer risk. The p53 and WRN proteins can engage in direct protein-protein interactions. We report that excess WRN elicits increased cellular p53 levels and potentiates p53-mediated apoptosis. Importantly, cells derived from WS patients exhibit an attenuated and delayed induction of p53 by UV or by the topoisomerase I inhibitor camptothecin. These results suggest that WRN may participate in the activation of p53 in response to certain types of DNA damage. Furthermore, the failure to induce p53 effectively may contribute to enhanced genomic instability and elevated cancer risk in WS patients.

Cells, Cultured↗

PubMed1999

Physical and functional interaction between p53 and the Werner's syndrome protein.

Werner's syndrome is a human autosomal recessive disorder leading to premature aging. The mutations responsible for this disorder have recently been localized to a gene (WRN) encoding a protein that possesses DNA helicase and exonuclease activities. Patients carrying WRN gene mutations exhibit an elevated rate of cancer, accompanied by increased genomic instability. The latter features are also characteristic of the loss of function of p53, a tumor suppressor that is very frequently inactivated in human cancer. Moreover, changes in the activity of p53 have been implicated in the onset of cellular replicative senescence. We report here that the WRN protein can form a specific physical interaction with p53. This interaction involves the carboxyl-terminal part of WRN and the extreme carboxyl terminus of p53, a region that plays an important role in regulating the functional state of p53. A small fraction of WRN can be found in complex with endogenous p53 in nontransfected cells. Overexpression of WRN leads to augmented p53-dependent transcriptional activity and induction of p21(Waf1) protein expression. These findings support the existence of a cross-talk between WRN and p53, which may be important for maintaining genomic integrity and for preventing the accumulation of aberrations that can give rise to premature senescence and cancer.

Aging, Premature↗

PubMed1999

p53-mediated apoptosis is attenuated in Werner syndrome cells.

The WRN DNA helicase is a member of the DExH-containing DNA helicase superfamily that includes XPB, XPD, and BLM. Mutations in WRN are found in patients with the premature aging and cancer susceptibility syndrome known as Werner syndrome (WS). p53 binds to the WRN protein in vivo and in vitro through its carboxyl terminus. WS fibroblasts have an attenuated p53- mediated apoptotic response, and this deficiency can be rescued by expression of wild-type WRN. These data support the hypothesis that p53 can induce apoptosis through the modulation of specific DExH-containing DNA helicases and may have implications for the cancer predisposition observed in WS patients.

Animals↗

PubMed1998

Comparison of methods for identifying transcription units and transcription map of the Werner syndrome gene region.

To isolate a human disease gene by positional cloning, a critical step is the identification of candidate genes from a targeted genomic region. We used cDNA selection, exon trapping, and genomic sequencing to identify 12 transcription units from a 1.4-Mb genomic region containing the Werner syndrome gene (WRN). This included sequencing of 650 kb in the region of the WRN gene, to date, the most DNA sequenced as part of a positional cloning effort. The result of this combined method was significant overlap among the transcription units identified by each method; yet, no one method identified all of the transcription units. We present here a comparison of the effectiveness and efficiency of these methods and present a transcription map of the Werner syndrome gene region.

Blotting, Northern↗

PubMed1998

An expression map from human chromosome 14q24.3.

We have constructed an expression map of chromosome 14q24.3 between markers D14S42 and D14S63. cDNA selection with YACs from 14q24.3 was used to generate expressed sequence tags (ESTs). The localization of ESTs was confirmed on a YAC contig. PCR products of ESTs were used as probes to screen cDNA libraries leading to the isolation of transcripts for known and unknown genes. In total, the expression map contains 7 known genes previously mapped to 14q24.3, 6 cDNA transcripts, and 15 anonymous ESTs. The addition of 21 unique transcribed loci from an approximately 5- to 7-Mb region of chromosome 14q24.3 will facilitate future efforts to identify human disease genes from this region.

Chromosome Mapping↗

PubMed1998

Aging-associated neuropathology in Werner syndrome.

Werner syndrome (WS) is an autosomal recessive disorder associated with evidence of accelerated systemic aging, but generally thought not to involve the central nervous system. We examined two WS cases utilizing a sensitive Bielschowsky silver stain and immunohistochemistry for amyloid beta peptide (A beta) and hyperphosphorylated tau. Extensive frontal and temporal lobe A beta deposition was observed in the oldest (age 57 years) WS case and restricted neurofibrillary pathology was seen in the medial temporal lobe of both cases. The severity of A beta deposition in the medial temporal lobe of the oldest case exceeded that observed in our control cases and that reported in the literature. Our findings suggest that the apparent accelerated aging observed in WS can involve the central nervous system and may implicate the recently observed WRN locus mutation associated with WS in the neuropathology of aging and aging-associated diseases.

Aged↗

PubMed1997

Mutations in the consensus helicase domains of the Werner syndrome gene. Werner's Syndrome Collaborative Group.

Werner syndrome (WS) is an autosomal recessive disease with a complex phenotype that is suggestive of accelerated aging. WS is caused by mutations in a gene, WRN, that encodes a predicted 1,432-amino-acid protein with homology to DNA and RNA helicases. Previous work identified four WS mutations in the 3' end of the gene, which resulted in predicted truncated protein products of 1,060-1,247 amino acids but did not disrupt the helicase domain region (amino acids 569-859). Here, additional WS subjects were screened for mutations, and the intron-exon structure of the gene was determined. A total of 35 exons were defined, with the coding sequences beginning in the second exon. Five new WS mutations were identified: two nonsense mutations at codons 369 and 889; a mutation at a splice-junction site, resulting in a predicted truncated protein of 760 amino acids; a 1-bp deletion causing a frameshift; and a predicted truncated protein of 391 amino acids. Another deletion is >15 kb of genomic DNA, including exons 19-23; the predicted protein is 1,186 amino acids long. Four of these new mutations either partially disrupt the helicase domain region or result in predicted protein products completely missing the helicase region. These results confirm that mutations in the WRN gene are responsible for WS. Also, the location of the mutations indicates that the presence or absence of the helicase domain does not influence the WS phenotype and suggests that WS is the result of complete loss of function of the WRN gene product.

Asian People↗

PubMed1996

Narrowing the position of the Werner syndrome locus by homozygosity analysis-extension of homozygosity analysis.

Werner syndrome (WS) is an autosomal recessive disorder characterized by the premature occurrence of many age-related features. Previously, the WS gene (WRN) was mapped between D8S131 and D8S87, in an 8.3-cM interval. In this study, regions of homozygosity in 36 WS patients from inbred families were searched for by genotyping for 35 dinucleotide repeat polymorphic markers to narrow down the WRN critical region. The region most consistently homozygous in these patients was between the D8S1219/D8S1220 cluster and D8S278, within a 4.4-cM interval. For 16 markers mapped in this interval, 24 WS patients (22 Japanese patients and 2 Caucasian patients) in whom consanguinity failed to be proved were also genotyped, under the assumption that some of these patients might still be from consanguineous marriages. The data were analyzed by Fisher's exact test with a 2 x 2 contingency table for the 22 Japanese patients, excluding the 2 Caucasian patients. The frequencies of homozygosity in the 22 patients at 10 of 16 markers tested were significantly higher than those detected in the general population. Analysis of homozygosity patterns indicated that the region most consistently homozygous was between D8S1445 and D8S278. Thus the WRN locus is most likely between the two markers D8S1445 and D8S278, in a 1.6-cM interval.

Asian People↗

PubMed1996

A YAC, P1, and cosmid contig and 17 new polymorphic markers for the Werner syndrome region at 8p12-p21.

A yeast artificial chromosome (YAC), P1, and cosmid clone contig was constructed for the Werner syndrome (WRN) region of chromosome 8p12-p21 and used to clone a candidate gene for WRN. This region also possibly contains a familial breast cancer locus. The contig was initiated by isolating YACs for the glutathione reductase (GSR) gene and extended in either direction by walking techniques. Sequence-tagged site (STS) markers were generated from subclones of 2 GSR YACs and used to identify P1 and cosmid clones. Additional STSs were generated from P1 and cosmid clones and from potential expressed sequences identified by cDNA selection and exon amplification methods. The final contig was assembled by typing 17 YACs, 20 P1 clones, and 109 cosmids for 54 STS markers. The WRN region could be spanned by 2 nonchimeric YACs covering approximately 1.4 Mb. A P1/cosmid contig was established covering the core 700-800 kb of the WRN region. Fifteen new short tandem repeat polymorphisms and 2 biallelic polymorphic markers were identified and included as STSs in the contig. Analysis of these markers in Werner syndrome subjects demonstrates that the candidate WRN gene is in a region of linkage disequilibrium.

Base Sequence↗

PubMed1996

Positional cloning of the Werner's syndrome gene.

Werner's syndrome (WS) is an inherited disease with clinical symptoms resembling premature aging. Early susceptibility to a number of major age-related diseases is a key feature of this disorder. The gene responsible for WS (known as WRN) was identified by positional cloning. The predicted protein is 1432 amino acids in length and shows significant similarity to DNA helicases. Four mutations in WS patients were identified. Two of the mutations are splice-junction mutations, with the predicted result being the exclusion of exons from the final messenger RNA. One of the these mutations, which results in a frameshift and a predicted truncated protein, was found in the homozygous state in 60 percent of Japanese WS patients examined. The other two mutations are nonsense mutations. The identification of a mutated putative helicase as the gene product of the WS gene suggests that defective DNA metabolism is involved in the complex process of aging in WS patients.

Aging↗

PubMed1996

Apolipoprotein E in Alzheimer's disease risk and case detection: a case-control study.

The objective of this study was to describe the association between the epsilon 4 allele of the apolipoprotein E gene (APOE E4) and Alzheimer's disease (AD) and to evaluate APOE E4 genotyping as a test for AD. The study base of this case-control study included about 23,000 persons 60 year of age or greater (a large health maintenance organization); the demographic characteristics of this group are similar to those of the surrounding area. Analysis focused on 234 Caucasian probable AD patients first identified between 1987 and 1993; and 304 cognitively intact controls of similar age, sex, and race who were randomly selected from the same study base. All cases were examined and diagnosed by study physicians using standard protocols. All subjects participate in continuing annual follow-up testing to verify their cognitive status. APOE genotypes were determined from blood samples using standard laboratory methods. Subject characteristics and diagnoses were obtained from interviews, diagnostic examination, or medical record review. Heterozygous E4 individuals had a crude odds ratio of 3.1 (2.1-4.5) for AD compared to those with no E4, while homozygous E4 subjects had an odds ratio of 34.3 (8.0-146.3) for AD. As an indicator of AD, having one E4 allele showed a sensitivity of 0.52 and a specificity of 0.74. Homozygous E4 genotype had a sensitivity of 0.23 and a specificity of 0.99 (when compared to non-E4 genotypes). Cardiovascular disease differed in cases and controls, but did not confound or modify the APOE E4-AI) association. In this study base, the APOE E4 allele was a significant risk factor. However, considering either homozygous or heterozygous E4 genotype as a screen or diagnostic marker for AD would miss many true cases and could misclassify many normals as AD.

Aged↗

PubMed1996

Homozygous and compound heterozygous mutations at the Werner syndrome locus.

The Werner syndrome (WS) is a rare autosomal recessive progeroid disorder. The Werner syndrome gene (WRN) has recently been identified as a member of the helicase family. Four distinct mutations were previously reported in three Japanese and one Syrian WS pedigrees. The latter mutation was originally described as a 4 bp deletion spanning a spliced junction. It is now shown that this mutation results in a 4 bp deletion at the beginning of an exon. Nine new WRN mutations in 10 additional WS patients, both Japanese and Caucasian, are described. These include three compound heterozygotes (one Japanese and two Caucasian). The new mutations are located all across the coding region.

Asian People↗

PubMed1996

Gender difference in apolipoprotein E-associated risk for familial Alzheimer disease: a possible clue to the higher incidence of Alzheimer disease in women.

Late-onset Alzheimer disease (AD) is associated with the apolipoprotein E (APOE)-epsilon4 allele. In late-onset familial AD, women have a significantly higher risk of developing the disease than do men. The aim of this study was to determine whether the gender difference in familial AD is a function of APOE genotype. We studied 58 late-onset familial AD kindreds. Kaplan-Meier survival analysis was used to assess genotype-specific distributions of age at onset. Odds ratios were estimated by logistic regression with adjustment for age and by conditional logistic regression with stratification on families. All methods detected a significant gender difference for the epsilon4 heterozygous genotype. In women, epsilon4 heterozygotes had higher risk than those without epsilon4; there was no significant difference between epsilon4 heterozygotes and epsilon4 homozygotes. In men, epsilon4 heterozygotes had lower risk than epsilon4 homozygotes; there was not significant difference between epsilon4 heterozygotes and those without epsilon4. A direct comparison of epsilon4 heterozygous men and women revealed a significant twofold increased risk in women. We confirmed these results in 15 autopsy-confirmed AD kindreds from the National Cell Repository at Indiana University Alzheimer Disease Center. These observations are consistent with the increased incidence of familial AD in women and may be a critical clue to the role of gender in the pathogenesis of AD.

Age of Onset↗

PubMed1996

Toward localization of the Werner syndrome gene by linkage disequilibrium and ancestral haplotyping: lessons learned from analysis of 35 chromosome 8p11.1-21.1 markers.

Werner syndrome (WS) is an autosomal recessive disorder characterized by premature onset of a number of age-related diseases. The gene for WS, WRN, has been mapped to the 8p 11.1-21.1 region with further localization through linkage disequilibrium mapping. Here we present the results of linkage disequilibrium and ancestral haplotype analyses of 35 markers to further refine the location of WRN. We identified an interval in this region in which 14 of 18 markers tested show significant evidence of linkage disequilibrium in at least one of the two populations tested. Analysis of extended and partial haplotypes covering 21 of the markers studied supports the existence of both obligate and probable ancestral recombinant events which localize WRN almost certainly to the interval between D8S2196 and D8S2186, and most likely to the narrower interval between D8S2168 and D8S2186. These haplotype analyses also suggest that there are multiple WRN mutations in each of the two populations under study. We also present a comparison of approaches to performing disequilibrium tests with multiallelic markers, and show that some commonly used approximations for such tests perform poorly in comparison to exact probability tests. Finally, we discuss some of the difficulties introduced by the high mutation rate at microsatellite markers which influence our ability to use ancestral haplotype analysis to localize disease genes.

Age of Onset↗

PubMed1995

Candidate gene for the chromosome 1 familial Alzheimer's disease locus.

A candidate gene for the chromosome 1 Alzheimer's disease (AD) locus was identified (STM2). The predicted amino acid sequence for STM2 is homologous to that of the recently cloned chromosome 14 AD gene (S182). A point mutation in STM2, resulting in the substitution of an isoleucine for an asparagine (N141l), was identified in affected people from Volga German AD kindreds. This N141l mutation occurs at an amino acid residue that is conserved in human S182 and in the mouse S182 homolog. The presence of missense mutations in AD subjects in two highly similar genes strongly supports the hypothesis that mutations in both are pathogenic.

Adult↗

PubMed1995

Apolipoprotein E genotypes and Alzheimer's disease in a community study of elderly African Americans.

As part of a community-based study of Alzheimer's disease (AD) in the African-American population age 65 and over, we have determined apolipoprotein E (Apo E) genotypes in 85 subjects (31 AD patients and 54 controls). The epsilon 4 allele of Apo E was strongly associated with AD in this population sample. The epsilon 4 allele frequency in AD patients was 40.3% compared with 13.9% in the control group, and 22.6% of the AD patients were homozygous for this allele compared with 3.7% of the control subjects (p = 0.01). This study extends the association of Apo E-epsilon 4 and AD to nonwhite populations and provides further evidence that the observed allelic association is biologically relevant.

Black or African American↗

PubMed1994

Cloning, sequencing, and mapping of the human chromosome 14 heat shock protein gene (HSPA2).

A genomic clone for the human heat shock protein (HSP) 70 gene located on chromosome 14 was isolated and sequenced. The gene, designated HSPA2, has a single open reading frame of 1917 bp that encodes a 639-amino acid protein with a predicted molecular weight of 70,030 Da. Analysis of the sequence indicates that HSPA2 is the human homologue of the murine Hsp70-2 gene with 91.7% identity in the nucleotide coding sequence and 98.2% in the corresponding amino acid sequence. HSPA2 has less amino acid homology to other members of the human HSP70 gene family, 83.3% to the heat-inducible HSP70-1 gene and 86.1% with the human heat shock cognate gene HSC70. HSPA2 is constitutively expressed in most tissues, with very high levels in testis and skeletal muscle. Significant but lower levels are also expressed in ovary, small intestine, colon, brain, placenta, and kidney. A yeast artificial chromosome (YAC) clone containing HSPA2 (YAC741H4) that also contained the polymorphic marker D14S63 was identified. This 670-kb YAC was mapped to 14q24.1 by fluorescence in situ hybridization (FISH). Subsequent two-color FISH and genetic mapping placed HSPA2/D14S63 proximal to the markers D14S57 and D14S77.

Amino Acid Sequence↗

PubMed1994

Integrated mapping analysis of the Werner syndrome region of chromosome 8.

The Werner syndrome locus (WRN) is located at 8p11-p12. To facilitate eventual cloning of the WRN gene, a 10,000-rad radiation-reduced hybrid (RH) cell panel was generated to map genetic markers, sequence-tagged sites (STSs), and genes in this region. A hamster cell line carrying an intact human chromosome 8 was fused with another hamster cell line. Two sets of hybrid cell panels from 2 separate fusions were generated; each panel consisted of 50 independent clones; 33 and 34 cell lines from the 2 fusions retained human chromsome material as determined by inter-Alu PCR. The combined panel was genotyped for 52 markers spanning the entire chromosome, including 10 genes, 29 anonymous polymorphic loci, and 13 STSs. Seventeen of these markers have not been previously described. Markers near the centromere were retained at a higher frequency than more distal markers. Fluorescence in situ hybridization was also used to localize and order a subset of the markers. A RH map of the WRN region was constructed using a maximum likelihood method, giving the following most likely order: D8S131-D8S339 (GSR)-D8S124-D8S278-D8S259-(D8S71)-D8S283- D8S87-D8S105-D8S135 (FGFR1)-D8S135PB-D8S255-ANK1. A genetic map of 15 short tandem repeat polymorphic loci in the WRN region was also constructed. The marker orders from the genetic and RH maps were consistent. In addition, an integrated map of 24 loci in the WRN region was generated using information from both genetic and RH mapping methods. A 1000:1 framework map for 6 loci (LPL-D8S136-D8S137-D8S87-FGFR1-ANK1) was determined by genetic mapping, and the resulting locus order was fixed during analysis of the RH genotype data. The resulting integrated map contained more markers than could confidently be ordered by either genetic or RH mapping alone.

Base Sequence↗