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Biomedical subjects

H Watkins

Publications and source records attributed to H Watkins.

At least 37 records · Page 2Linked to original sources
PubMed1999

Human stromelysin gene promoter activity is modulated by transcription factor ZBP-89.

Matrix metalloproteinase expression is under strict regulation in physiological conditions. Disruption of the regulatory mechanisms can lead to tissue destruction and is associated with tumour invasion and metastasis. Using the one-hybrid assay technique with a cis-element in the promoter region of the stromelysin (matrix metalloproteinase-3) gene, a cDNA encoding a transcription factor termed ZBP-89 was obtained. The interaction between ZBP-89 and the stromelysin promoter element was confirmed by electrophoretic mobility shift assays with a recombinant ZBP-89. Reporter gene expression under the control of the stromelysin promoter in transiently transfected cells was significantly increased when the cells were cotransfected with a ZBP-89 expression construct. These results indicate that ZBP-89 interacts with the stromelysin promoter and upregulates its activity. As ZBP-89 expression is known to be increased in gastric carcinoma cells, induction of stromelysin expression may be a significant factor in tumour metastasis.

DNA-Binding Proteins↗
PubMed1999

Functional polymorphism in the regulatory region of gelatinase B gene in relation to severity of coronary atherosclerosis.

BACKGROUND: Gelatinase B, a matrix metalloproteinase that has proteolytic activity against connective tissue proteins, has been suggested to be important in the connective tissue remodeling processes associated with atherogenesis and plaque rupture. This study tested the hypothesis that sequence variation in the promoter region of the gelatinase B gene influences its expression, predisposing individuals carrying certain genetic variants to more severe atherosclerosis. METHODS AND RESULTS: Single-strand conformation polymorphism analysis was carried out to search the promoter region of the gene encoding gelatinase B for naturally occurring genetic variation. As a result, an unreported common polymorphism was detected, which arose from a cytosine (C) to thymidine (T) transition at position -1562 relative to the start of transcription. Transient transfection experiments and DNA-protein interaction assays indicated that the T allele had a higher promoter activity than the C allele, which appeared to be due to preferential binding of a putative transcription repressor protein to the C allelic promoter. A sample of 584 male patients with myocardial infarction and 645 age-matched male healthy control subjects were genotyped. The allele frequencies were not significantly different between the cases and control subjects. However, in 374 patients with available angiographic data, 26% of those carrying 1 or 2 copies of the T allele had >50% stenosis in 3 coronary arteries, whereas only 15% of C/C homozygotes had triple-vessel disease. CONCLUSIONS: These data suggest that this functional genetic variation influences gelatinase B gene promoter activity in an allele-specific manner and has an effect on atherosclerotic phenotype.

Adult↗
PubMed1999

Genetic variation at the matrix metalloproteinase-9 locus on chromosome 20q12.2-13.1.

Allelic association methods are better suited than linkage analysis for mapping of susceptibility genes that confer modest increases in risk in complex diseases. In both family- and population-based association studies, it is very useful to have prior knowledge of all sequence variants and the degree of linkage disequilibrium in a candidate gene region. In this study, we scanned sequence variants in a 2.2-kb promoter sequence and all 13 exons (totalling 3.3 kb) of the matrix metalloproteinase-9 gene, which is associated with coronary heart disease and a candidate for other diseases involving connective tissue remodelling, such as cancer metastasis. The sequences had a total of ten variable sites, four in the promoter, five in the coding region (three of which alter the amino acid encoded) and one in the 3' untranslated sequence. Sequence inspection suggests that some of the variants will have a functional impact on either level of expression or enzymatic activity. Tight linkage disequilibrium was detected between variants across the entire length of the gene (approximately 9 kb), and frequencies of different haplotypes were determined. The data provide an essential tool for studies of the possible contribution of genetic variation at the matrix metalloproteinase-9 locus to genetically determined susceptibility to a number of important diseases. The results also provide experimental data on the extent of linkage disequilibrium in the general population, which is yet to be resolved.

3' Untranslated Regions↗
PubMed1999

Properties of mutant contractile proteins that cause hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is one of the most frequently occurring inherited cardiac disorders, affecting up to 1 in 500 of the population. Molecular genetic analysis has shown that HCM is a disease of the sarcomere, caused by mutations in certain contractile protein genes. To date seven disease-associated genes have been identified, those encoding beta-myosin heavy chain, both regulatory and essential myosin light chains, myosin binding protein-C, cardiac troponin T, cardiac troponin I and alpha-tropomyosin. Here we review the analyses of how these mutations affect the in vitro contractile protein function and the hypotheses derived to explain the development of the disease state.

Cardiomyopathy, Hypertrophic↗
PubMed1999

Hereditary postlingual sensorineural hearing loss mapping to chromosome Xq21.

BACKGROUND: Mutations on the X-chromosome clinically manifesting different phenotypes of hearing loss have been mapped to the long arm at different loci, DFN1-DFN3. Another defect in a family with sex-linked, postlingual, progressive sensorineural hearing loss was mapped to Xq. METHODS: Clinically, the family was evaluated by physical and audiometric examination of 17 members including computerized tomographic (CT) evaluation of the proband. Molecular evaluation consisted of polymerase chain reaction amplification of patient genomic DNA and resolution 32P-labeled fragments by polyacrylamide gels. Inheritance of DNA alleles and deafness were analyzed using the MLINK computer program. RESULTS: Five affected males demonstrated symmetrical sensorineural hearing loss as significant as 100 decibels (dB). Two carrier females had a milder loss with frequency findings of 10 dB to 60 dB. Computerized tomography (CT) evaluation of the temporal bones of the proband was normal. The odds were 200:1 that the responsible gene was linked to locus DXS986 (maximum lod score = 2.3 at 0 = 0). Analysis of recombination events defined by family members demonstrates that the responsible gene lies in a 21 cM (30 MB) interval, between loci DXS12175 and 1106. The disease locus in this family does not appear to map to DFN1 or DFN3. CONCLUSION: The family described here, with affected males who have progressive, postlingual sensorineural hearing loss and mildly affected females maps most compatibly to the DFN2 locus. Analysis of hereditary deafness in this family refines the DFN2 locus to a 9.2 Mb region in chromosome X band q21 between DXS990 and DXS106.

Adolescent↗
PubMed1998

Functional analyses of troponin T mutations that cause hypertrophic cardiomyopathy: insights into disease pathogenesis and troponin function.

Mutations in a number of cardiac sarcomeric protein genes cause hypertrophic cardiomyopathy (HCM). Previous findings indicate that HCM-causing mutations associated with a truncated cardiac troponin T (TnT) and missense mutations in the beta-myosin heavy chain share abnormalities in common, acting as dominant negative alleles that impair contractile performance. In contrast, Lin et al. [Lin, D., Bobkova, A., Homsher, E. & Tobacman, L. S. (1996) J. Clin. Invest. 97, 2842-2848] characterized a TnT point mutation (Ile79Asn) and concluded that it might lead to hypercontractility and, thus, potentially a different mechanism for HCM pathogenesis. In this study, three HCM-causing cardiac TnT mutations (Ile79Asn, Arg92Gln, and DeltaGlu160) were studied in a myotube expression system. Functional studies of wild-type and mutant transfected myotubes revealed that all three mutants decreased the calcium sensitivity of force production and that the two missense mutations (Ile79Asn and Arg92Gln) increased the unloaded shortening velocity nearly 2-fold. The data demonstrate that TnT can alter the rate of myosin cross-bridge detachment, and thus the troponin complex plays a greater role in modulating muscle contractile performance than was recognized previously. Furthermore, these data suggest that these TnT mutations may cause disease via an increased energetic load on the heart. This would represent a second paradigm for HCM pathogenesis.

Animals↗
PubMed1998

Mutations in the gene for cardiac myosin-binding protein C and late-onset familial hypertrophic cardiomyopathy.

BACKGROUND: Mutations in the gene for cardiac myosin-binding protein C account for approximately 15 percent of cases of familial hypertrophic cardiomyopathy. The spectrum of disease-causing mutations and the associated clinical features of these gene defects are unknown. METHODS: DNA sequences encoding cardiac myosin-binding protein C were determined in unrelated patients with familial hypertrophic cardiomyopathy. Mutations were found in 16 probands, who had 574 family members at risk of inheriting these defects. The genotypes of these family members were determined, and the clinical status of 212 family members with mutations in the gene for cardiac myosin-binding protein C was assessed. RESULTS: Twelve novel mutations were identified in probands from 16 families. Four were missense mutations; eight defects (insertions, deletions, and splice mutations) were predicted to truncate cardiac myosin-binding protein C. The clinical expression of either missense or truncation mutations was similar to that observed for other genetic causes of hypertrophic cardiomyopathy, but the age at onset of the disease differed markedly. Only 58 percent of adults under the age of 50 years who had a mutation in the cardiac myosin-binding protein C gene (68 of 117 patients) had cardiac hypertrophy; disease penetrance remained incomplete through the age of 60 years. Survival was generally better than that observed among patients with hypertrophic cardiomyopathy caused by other mutations in the genes for sarcomere proteins. Most deaths due to cardiac causes in these families occurred suddenly. CONCLUSIONS: The clinical expression of mutations in the gene for cardiac myosin-binding protein C is often delayed until middle age or old age. Delayed expression of cardiac hypertrophy and a favorable clinical course may hinder recognition of the heritable nature of mutations in the cardiac myosin-binding protein C gene. Clinical screening in adult life may be warranted for members of families characterized by hypertrophic cardiomyopathy.

Adolescent↗
PubMed1997

Effects of two hypertrophic cardiomyopathy mutations in alpha-tropomyosin, Asp175Asn and Glu180Gly, on Ca2+ regulation of thin filament motility.

The functional properties of wild type alpha-tropomyosin expressed in E. coli with an alanine-serine N-terminal leader (AS-alpha-Tm) were compared with those of AS-alpha-Tm with either of two missense mutations (Asp175Asn and Glu180Gly) shown to cause familial hypertrophic cardiomyopathy (FHC). Wild type AS-alpha-Tm and AS-alpha-Tm(Asp175Asn) binding to actin was indistinguishable from rabbit skeletal muscle ab-tropomyosin whilst the affinity of AS-alpha-Tm(Glu180Gly) was about threefold weaker. In vitro motility assays were performed with AS-alpha-tropomyosin incorporated into skeletal muscle actin-rhodamine phalloidin filaments moving over skeletal muscle heavy meromyosin. Under relaxing conditions (pCa9), troponin added to actin filaments containing AS-alpha-tropomyosin or mutant tropomyosins resulted in normal switch-off, with a decrease in the fraction filaments moving from >80% to <20%. Under activating conditions (pCa5), troponin had a minor effect upon actin-AS-alpha-tropomyosin filament velocity (increased by 5 +/- 1%, n=10), whereas the velocity increased by 18 +/- 3% (n=7) with actin filaments containing AS-alpha-tropomyosin(Asp175Asn) and by 21 +/- 2% (n=8) with filaments containing AS-alpha-tropomyosin(Glu180Gly) (p<0.05 compared with AS-alpha-tropomyosin). Thus FHC mutations in alpha-tropomyosin produce detectable changes in the Ca2+-regulation of thin filaments, presumably via altered interaction with troponin.

Actins↗
PubMed1997

Sudden death due to troponin T mutations.

OBJECTIVES: This study was designed to verify initial observations of the clinical and prognostic features of hypertrophic cardiomyopathy caused by cardiac tropnin T gene mutations. BACKGROUND: The most common cause of sudden cardiac death in the young is hypertrophic cardiomyopathy, which is usually familial. Mutations causing familial hypertrophic cardiomyopathy have been identified in a number of contractile protein genes, raising the possibility of genetic screening for subjects at risk. A previous report suggested that mutations in the cardiac troponin T gene were notable because they were associated with a particularly poor prognosis but only mild hypertrophy. Given the variability of some genotype:phenotype correlations, further analysis of cardiac troponin T mutations has been a priority. METHODS: Deoxyribonucleic acid from subjects with hypertrophic cardiomyopathy was screened for cardiac troponin T mutations using a ribonuclease protection assay. Polymerase chain reaction-based detection of a novel mutation was used to genotype members of two affected pedigrees. Gene carriers were examined by echocardiography and electrocardiology, and a family history was obtained. RESULTS: A novel cardiac troponin T gene mutation, arginine 92 tryptophan, was identified in 19 of 48 members of two affected pedigrees. The clinical phenotype was characterized by minimal hypertrophy (mean [+/-SD] maximal ventricular wall thickness 11.3 +/- 5.4 mm) and low disease penetrance by clinical criteria (40% by echocardiography) but a high incidence of sudden cardiac death (mean age 17 +/- 9 years). CONCLUSIONS: These data support the observation that apparently diverse cardiac troponin T gene mutations produce a consistent disease phenotype. Because this is one of poor prognosis, despite deceptively mild or undetectable hypertrophy, genotyping at this locus may be particularly informative in patient management and counselling.

Biomarkers↗
PubMed1997

Clinical features of hypertrophic cardiomyopathy caused by mutation of a "hot spot" in the alpha-tropomyosin gene.

OBJECTIVES: We studied the clinical and genetic features of familial hypertrophic cardiomyopathy (FHC) caused by an Asp175Asn mutation in the alpha-tropomyosin gene in affected subjects from three unrelated families. BACKGROUND: Correlation of genotype and phenotype has provided important information in FHC caused by beta-cardiac myosin and cardiac troponin T mutations. Comparable analyses of hypertrophic cardiomyopathy caused by alpha-tropomyosin mutations have been hampered by the rarity of these genetic defects. METHODS: The haplotypes of three kindreds with FHC due to an alpha-tropomyosin gene mutation, Asp175Asn, were analyzed. The cardiac histopathologic findings of this mutation are reported. Distribution of left ventricular hypertrophy in affected members was assessed by two-dimensional echocardiography, and patient survival rates were compared. RESULTS: Genetic studies defined unique haplotypes in the three families, demonstrating that independent mutations caused the disease in each. The Asp175Asn mutation caused cardiac histopathologic findings of myocyte hypertrophy, disarray and replacement fibrosis. The severity and distribution of left ventricular hypertrophy varied considerably in affected members from the three families (mean maximal wall thickness +/- SD: 24 +/- 4.5 mm in anterior septum of Family DT; 15 +/- 2.7 mm in anterior septum and free wall of Family DB; 18 +/- 2.1 mm in posterior septum of Family MI), but survival was comparable and favorable. CONCLUSIONS: Nucleotide residue 579 in the alpha-tropomyosin gene may have increased susceptibility to mutation. On cardiac histopathologic study, defects in this sarcomere thin filament component are indistinguishable from other genetic etiologies of hypertrophic cardiomyopathy. The Asp175Asn mutation can elicit different morphologic responses, suggesting that the hypertrophic phenotype is modulated not by genetic etiologic factors alone. In contrast, prognosis reflected genotype; near normal life expectancy is found in hypertrophic cardiomyopathy caused by the alpha-tropomyosin mutation Asp175Asn.

Adolescent↗
PubMed1997

Dimensions of quality of life expressed by men treated for metastatic prostate cancer.

Men who pursue active treatment for metastatic prostate cancer face a choice between medical or surgical castration. While both alternatives have documented side-effects (e.g. loss of libido, breast enlargement and tenderness, hot flashes, and nausea), their psychosocial impacts are not well understood. As part of a study of patients' treatment decision making, we have sought to construct a patient-based measure of the salient disease and treatment-related qualities of life experienced by these men subsequent to treatment. Focus groups (15 with patients, two with wives) were used to develop candidate Likert scale questionnaire items representing quality of life issues that patients said were important. These items were combined with assessments of symptoms, comorbidity, and generic measures of functional status and well-being in a mail survey of patients treated at the Houston VAMC and two other Houston hospitals (n = 201, response rate = 63%). Psychometric analyses (principal components and multitrait scaling) were used to identify distinct dimensions of life quality; correlations with generic measures, and symptom reports were used in validation analyses. Qualitative analyses of focus group data identified three major domains of life quality: self-perceptions, anxiety about the effects of treatment, and concern with the process of decision making and treatment. Psychometric analyses identified nine reliable and valid indicators of prostate cancer-related quality of life: body image, sexual problems, spouse affection, spouse worry, masculinity, cancer-related self-image, cancer distress, cancer acceptance, and regret of treatment decision. Internal consistency (alpha) ranged form 0.71 to 0.90. Correlations with reference scales (e.g. MOS Mental Health Index, Profile of Mood States) and symptom status supported concurrent validity. Prostate cancer patients perceive a number of important psychosocial consequences of their treatment. These consequences are represented by nine scales comprising a brief (35 items) disease and treatment sensitive health-related quality of life instrument, which we will use in monitoring the outcomes of patients' treatment choices.

Adaptation, Psychological↗
PubMed1997

The molecular genetics of hypertrophic cardiomyopathy.

The study of hypertrophic cardiomyopathy has been at the vanguard of molecular genetic investigation into inherited diseases of the cardiovascular system for the greater part of the last decade. These studies have shown it to be a disease of sarcomeric contractile proteins and have highlighted its genetic heterogeneity. There are now seven known genetic loci and six disease genes associated with the condition. The biology of the mutant polypeptides has been studied in vitro, and animal models are being developed. Increased understanding gained from these studies has clarified features of the condition at the clinical level and has had an impact on management of patients. It is hoped that this work will lead to the development of novel therapies for both hypertrophic cardiomyopathy and acquired forms of left ventricular hypertrophy.

Animals↗