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Calum A MacRae

Publications and source records attributed to Calum A MacRae.

9 recordsLinked to original sources
PubMed2004

Mutations in the desmosomal protein plakophilin-2 are common in arrhythmogenic right ventricular cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with fibrofatty replacement of cardiac myocytes, ventricular tachyarrhythmias and sudden cardiac death. In 32 of 120 unrelated individuals with ARVC, we identified heterozygous mutations in PKP2, which encodes plakophilin-2, an essential armadillo-repeat protein of the cardiac desmosome. In two kindreds with ARVC, disease was incompletely penetrant in most carriers of PKP2 mutations.

Adolescent↗
PubMed2004

Chemical suppression of a genetic mutation in a zebrafish model of aortic coarctation.

Conventional drug discovery approaches require a priori selection of an appropriate molecular target, but it is often not obvious which biological pathways must be targeted to reverse a disease phenotype. Phenotype-based screens offer the potential to identify pathways and potential therapies that influence disease processes. The zebrafish mutation gridlock (grl, affecting the gene hey2) disrupts aortic blood flow in a region and physiological manner akin to aortic coarctation in humans. Here we use a whole-organism, phenotype-based, small-molecule screen to discover a class of compounds that suppress the coarctation phenotype and permit survival to adulthood. These compounds function during the specification and migration of angioblasts. They act to upregulate expression of vascular endothelial growth factor (VEGF), and the activation of the VEGF pathway is sufficient to suppress the gridlock phenotype. Thus, organism-based screens allow the discovery of small molecules that ameliorate complex dysmorphic syndromes even without targeting the affected gene directly.

Animals↗
PubMed2004

Integrin-linked kinase regulates endothelial cell survival and vascular development.

Integrin-linked kinase (ILK) is a phosphoinositide 3-kinase-dependent serine/threonine kinase that interacts with beta integrins. Here we show that endothelial cell (EC)-specific deletion of ILK in mice confers placental insufficiency with decreased labyrinthine vascularization, yielding no viable offspring. Deletion of ILK in zebra fish using antisense morpholino oligonucleotides results in marked patterning abnormalities of the vasculature and is similarly lethal. To dissect potential mechanisms responsible for these phenotypes, we performed ex vivo deletion of ILK from purified EC of adult mice. We observed downregulation of the active-conformation of beta1 integrins with a striking increase in EC apoptosis associated with activation of caspase 9. There was also reduced phosphorylation of the ILK kinase substrate, Akt. However, phenotypic rescue of ILK-deficient EC by wild-type ILK, but not by a constitutively active mutant of Akt, suggests regulation of EC survival by ILK in an Akt-independent manner. Thus, endothelial ILK plays a critical role in vascular development through integrin-matrix interactions and EC survival. These data have important implications for both physiological and pathological angiogenesis.

Animals↗
PubMed2003

Carotid intima-media thickness is associated with premature parental coronary heart disease: the Framingham Heart Study.

BACKGROUND: A family history of coronary heart disease (CHD) is an independent risk factor for cardiovascular events. However, the mechanisms underlying this susceptibility have not been fully elucidated. We hypothesized that an important mediator of the familial predisposition to CHD is subclinical atherosclerosis, which is detectable by noninvasive imaging. METHODS AND RESULTS: We studied 1662 subjects (mean age 57, 51% women) in the Framingham Offspring Study who underwent carotid ultrasonography and had both biological parents in the original (parental) cohort. Parental CHD events were validated prospectively by a physician endpoint committee. The associations of carotid intima-media thickness (IMT) with premature parental CHD (occurring before age 60) and any parental CHD (no age restriction) were examined in age- and multivariable-adjusted analyses. Age-adjusted mean internal carotid IMT was higher in subjects who had at least one parent with premature CHD than in those without a validated parental history of premature CHD (men 1.13 versus 1.04 mm, P<0.01; women 0.92 versus 0.85 mm, P=0.03). In both sexes, these differences remained significant after adjustment for cardiovascular risk factors. In analyses without a restriction on parental age of CHD onset, the association between carotid IMT and parental CHD was not statistically significant. There was also no significant association of common carotid IMT with premature or any parental CHD. CONCLUSIONS: These findings suggest that subclinical atherosclerosis, assessed in the carotid arteries, is more prevalent in individuals with a family history of CHD. Early-onset parental CHD, in particular, identifies offspring with a strong familial predisposition to atherosclerosis.

Adult↗
PubMed2003

Locus for atrial fibrillation maps to chromosome 6q14-16.

BACKGROUND: Atrial fibrillation (AF), the most common clinical arrhythmia, is a major cause of morbidity and mortality. Although AF is often associated with other cardiovascular conditions, many patients present without an obvious etiology. Inherited forms of AF exist, but the causative gene has been defined only in a single family. We have identified a large family (family FAF-1) in which AF segregates as a Mendelian trait. METHODS AND RESULTS: Thirty-four family members were evaluated by 12-lead ECG, echocardiogram, 24-hour Holter monitoring, and laboratory studies. Individuals with electrocardiographically documented AF were defined as affected. Subjects were considered unaffected if they were >60 years of age, had no personal history of AF, and had no offspring with a history of AF. DNA was extracted and genotypic analyses were performed using polymorphic microsatellite markers. Evidence of linkage was obtained on chromosome 6, with a peak 2-point logarithm of the odds (LOD) score of 3.63 (theta=0) at the marker D6S1021. A maximal multipoint LOD score of 4.9 was obtained between D6S286 and D6S1021, indicating odds of approximately 100 000:1 in favor of this interval as the location of the gene defect responsible for AF in this family. The LOD scores were robust to changes in penetrance and allele frequency. Haplotype analyses further supported this minimal genetic interval. CONCLUSIONS: We have mapped a novel locus for AF to chromosome 6q14-16. The identification of the causative gene in this interval will be an important step in understanding the fundamental mechanisms of AF.

Adult↗
PubMed2003

Drugs that induce repolarization abnormalities cause bradycardia in zebrafish.

BACKGROUND: Drug-induced QT prolongation and torsades de pointes remain significant and often unpredictable clinical problems. Current in vitro preclinical assays are limited by biological simplicity, and in vivo models suffer from expense and low throughput. METHODS AND RESULTS: During a screen for the effects of 100 small molecules on the heart rate of the zebrafish, Danio rerio, we found that drugs that cause QT prolongation in humans consistently caused bradycardia and AV block in the zebrafish. Of 23 such drugs tested, 18 were positive in this initial screen. Poor absorption explained 4 of 5 false-negative results, as demonstrated by microinjection. Overall, 22 of 23 compounds that cause repolarization abnormalities were positive in this assay. Antisense "knockdown" of the zebrafish KCNH2 ortholog yielded bradycardia in a dose dependent manner confirming the effects of reduction of repolarizing potassium current in this model. Classical drug-drug interactions between erythromycin and cisapride, as well as cimetidine and terfenadine, were also reproduced. CONCLUSION: This simple high-throughput assay is a promising addition to the repertoire of preclinical tests for drug-induced repolarization abnormalities. The genetic tractability of the zebrafish will allow the exploration of heritable modifiers of such drug effects.

Animals↗