Abstract 1889: CHIP-based Sequence Analysis of 34 Cardiomyopathy Genes Reveals New Genes Involved in HCM and DCM and Multiple Pathogenic Mutations in Single Patients
Inherited cardiomyopathy is a frequent cardiac disease with a prevalence of 1:500 (HCM) to 1: 2500 (DCM). Due to the large amount of genes involved, the clinical heterogeneity and the laborious screening methods, it is difficult to unravel rapidly the genetic cause in all cases. Current diagnostic screening solves only 60 –70% of the families by testing a limited number of genes in an often time-consuming sequential fashion and usually stops when a pathogenic mutation has been identified. However, double pathogenic mutations seem to be present in 5–10% of the familial cases. In order to create a fast, parallel genetic screening pipeline for inherited cardiomyopathy, we designed a resequencing array (CardioCHIP) covering 34 genes in duplicate (300Kb). We included genes known to be involved in DCM, HCM, LVNC and LGMD and candidate genes based on their presence in the sarcomere and Z-disc. All exons and flanking introns (38bp) were included on the CardioCHIP, covering the heart- and muscle-specific RNA-isoforms. The 5′UTR and 3′UTR regions and, for a selection of genes, the promoter regions were included. The genes, which were interrogated by the CardioCHIP, were amplified in 152 LR-PCR covering 395 exons, resulting in a sequence of 146.541 nucleotides. So far, 250 patients were sequenced for all 34 cardiomyopathy genes. The mutation detection rate is around 99% and about 98% of the novel exonic variants can be confirmed by conventional sequence analysis. In addition to mutations detected in the 13 genes routinely tested for HCM or DCM, we identified mutations in the 21 additional genes, some of which were the first for those new candidate genes. We identified in several patients up to 4 pathogenic mutations, involved in different pathogenic processes. Our data indicate that parallel analysis of multiple genes is a prerequisite for genetic testing in HCM and DCM to identify rapidly the genetic cause. Due to the potential presence of multiple mutations and to prevent misinterpretation, it is essential to test all genes in all patients and not proceed solely on the first genetic defect identified. This is also the case for the relatives at risk, which would imply that for proper prognosis and preventive treatment all candidate genes should be tested in parallel for each individual.