Noncompaction of the Ventricular Myocardium Is Associated with a De Novo Mutation in the β-Myosin Heavy Chain Gene

Noncompaction of the ventricular myocardium (NVM) is the morphological hallmark of a rare familial or sporadic unclassified heart disease of heterogeneous origin. NVM results presumably from a congenital developmental error and has been traced back to single point mutations in various genes. The objective of this study was to determine the underlying genetic defect in a large German family suffering from NVM. Twenty four family members were clinically assessed using advanced imaging techniques. For molecular characterization, a genome-wide linkage analysis was undertaken and the disease locus was mapped to chromosome 14ptel-14q12. Subsequently, two genes of the disease interval, MYH6 and MYH7 (encoding the α- and β-myosin heavy chain, respectively) were sequenced, leading to the identification of a previously unknown de novo missense mutation, c.842G>C, in the gene MYH7. The mutation affects a highly conserved amino acid in the myosin subfragment-1 (R281T). In silico simulations suggest that the mutation R281T prevents the formation of a salt bridge between residues R281 and D325, thereby destabilizing the myosin head. The mutation was exclusively present in morphologically affected family members. A few members of the family displayed NVM in combination with other heart defects, such as dislocation of the tricuspid valve (Ebstein's anomaly, EA) and atrial septal defect (ASD). A high degree of clinical variability was observed, ranging from the absence of symptoms in childhood to cardiac death in the third decade of life. The data presented in this report provide first evidence that a mutation in a sarcomeric protein can cause noncompaction of the ventricular myocardium

Genetic counselling for hypertrophic cardiomyopathy: are we ready for it?

Abstract Hypertrophic cardiomyopathy (HCM) is a dominant genetic disorder of the myocardium associated with dysfunctional contractile proteins. The major risk of HCM is sudden cardiac death, which may occur even in asymptomatic carriers. Causes are highly heterogeneous. Over 140 different mutations in nine sarcomeric genes have been described to date. The majority of cases (80% or more) may eventually be traced to one of these genes. Although genetic counselling is suggested even if mutations are not known, molecular diagnosis implies new options such as carrier identification or - theoretically - preclinical risk stratification. A scheme according to which cardiologists and clinical and molecular geneticists could cooperate in counselling patients and managing HCM clinically is proposed.</p

The polymerase chain reaction: an improved method for the analysis of nucleic acids

The polymerase chain reaction (PCR) is a method for the selective amplification of DNA or RNA segments of up to 2 kilobase-pairs (kb) or more in length. Synthetic oligonucleotides flanking sequences of interest are used in repeated cycles of enzymatic primer extension in opposite and overlapping directions. The essential steps in each cycle are thermal denaturation of double-stranded target molecules, primer annealing to both strands and enzymatic synthesis of DNA. The use of the heat-stable DNA polymerase from the archebacterium Thermus aquaticus (Taq polymerase) makes the reaction amenable to automation. Since both strands of a given DNA segment are used as templates, the number of target sequences increases exponentially. The reaction is simple, fast and extremely sensitive. The DNA or RNA content of a single cell is sufficient to detect a specific sequence. This method greatly facilitates the diagnosis of mutations or sequence polymorphisms of various types in human genetics, and the detection of pathogenic components and conditions in the context of clinical research and diagnostics; it is also useful in simplifying complex analytical or synthetic protocols in basic molecular biology. This article describes the principles of the reaction and discusses the applications in different areas of biomedical research

The 2373insG mutation in the MYBPC3 gene is a founder mutation, which accounts for nearly one-fourth of the HCM cases in the Netherlands

AIMS: Hypertrophic cardiomyopathy (HCM) is caused by mutations in genes that encode sarcomeric proteins. In this study we investigated the involvement of the sarcomeric myosin binding protein C in the Dutch HCM population. METHODS AND RESULTS: We initially screened 22 Dutch index patients for mutations in the MYBPC3 gene, which revealed four different mutations in 14 patients. The 2373insG mutation was identified in 10 apparently unrelated patients. A subsequent screening for the 2373insG mutation in a group of another 237 unrelated HCM patients revealed 50 additional carriers of the same genetic defect. Genotyping with polymorphic repeat markers and intragenic SNPs of the 60 Dutch as well as two German and five North American 2373insG carriers indicated they all share the same haplotype. CONCLUSION: The 2373insG mutation accounts for almost one-fourth of all HCM cases in the Netherlands (60/259), which is predominantly present in the northwestern part of the country (22/66) and is a founder mutation probably originating from the Netherlands

Pedigree of family DU-11 with haplotypes on chromosome 14 and segregation of <i>MYH7</i> mutation R281T (c.842G>C).

<p>Family members are shown by filled black symbols (affected), by half filled symbols (partially affected), open symbols (unaffected) and gray symbols (unknown affection status). An arrow points to the index patient. The disease associated haplotype is shown by filled black bars. Markers within the minimum disease associated haplotype are boxed. Below the haplotypes of each individual the occurrence of wild-type (+) and mutant <i>MYH7</i> alleles (−) is indicated.</p