Rapid detection of genetic variants in hypertrophic cardiomyopathy by custom DNA resequencing array in clinical practice.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease (1/500) and the most common cause of sudden cardiac death in young people. Pathogenic mutation detection of HCM is having a growing impact on the medical management of patients and their families. However, the remarkable genetic and allelic heterogeneity makes molecular analysis by conventional methods very time-consuming, expensive and difficult to realise in a routine diagnostic molecular laboratory. METHOD AND RESULTS: The authors used their custom DNA resequencing array which interrogates all possible single-nucleotide variants on both strands of all exons (n=160), splice sites and 5'-untranslated region of 12 HCM genes (27 000 nucleotides). The results for 122 unrelated patients with HCM are presented. Thirty-three known or novel potentially pathogenic heterozygous single-nucleotide variants were identified in 38 patients (31%) in genes MYH7, MYBPC3, TNNT2, TNNI3, TPM1, MYL3 and ACTC1. CONCLUSIONS: Although next-generation sequencing will replace all large-scale sequencing platforms for inherited cardiac disorders in the near future, this HCM resequencing array is currently the most rapid, cost-effective and reasonably efficient technology for first-tier mutation screening of HCM in clinical practice. Because of its design, the array is also an appropriate tool for initial screening of other inherited forms of cardiomyopathy.

A DNA resequencing array for pathogenic mutation detection in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a heterogeneous autosomal dominant cardiac disorder with a prevalence of 1 in 500. Over 450 different pathogenic mutations in at least 16 genes have been identified so far. The large allelic and genetic heterogeneity of HCM requires high-throughput, rapid, and affordable mutation detection technologies to efficiently integrate molecular screening into clinical practice. We developed a custom DNA resequencing array that contains both strands of all coding exons (160), splice-site junctions, and 5'UTR regions of 12 genes that have been clearly implicated in HCM (MYH7, MYBPC3, TNNT2, TPM1, TNNI3, MYL3, MYL2, CSRP3, PLN, ACTC, TNNC1, and PRKAG2). We analyzed a first series of 38 unrelated patients with HCM (17 familial, 21 sporadic). A total of 953,306 bp across the 38 patients were sequenced with a mean nucleotide call rate of 96.92% (range: 93-99.9%). Pathogenic mutations (single nucleotide substitutions) in MYH7, MYBPC3, TNNI3, and MYL3 (six known and six novel) were identified in 60% (10/17) of familial HCM and 10% of sporadic cases (2/21). The high-throughput HCM resequencing array is the most rapid and cost-effective tool for molecular testing of HCM to date; it thus has considerable potential in diagnostic and predictive testing, and prognostic stratification.

DNAI1 mutations explain only 2% of primary ciliary dykinesia.

BACKGROUND: Primary ciliary dyskinesia (PCD) is a rare recessive hereditary disorder characterized by dysmotility to immotility of ciliated and flagellated structures. Its main symptoms are respiratory, caused by defective ciliary beating in the epithelium of the upper airways (nose, bronchi and paranasal sinuses). Impairing the drainage of inhaled microorganisms and particles leads to recurrent infections and pulmonary complications. To date, 5 genes encoding 3 dynein protein arm subunits (DNAI1, DNAH5 and DNAH11), the kinase TXNDC3 and the X-linked RPGR have been found to be mutated in PCD. OBJECTIVES: We proposed to determine the impact of the DNAI1 gene on a cohort of unrelated PCD patients (n = 104) recruited without any phenotypic preselection. METHODS: We used denaturing high-performance liquid chromatography and sequencing to screen for mutations in the coding and splicing site sequences of the gene DNAI1. RESULTS: Three mutations were identified: a novel missense variant (p.Glu174Lys) was found in 1 patient and 2 previously reported variants were identified (p.Trp568Ser in 1 patient and IVS1+2_3insT in 3 patients). Overall, mutations on both alleles of gene DNAI1 were identified in only 2% of our clinically heterogeneous cohort of patients. CONCLUSION: We conclude that DNAI1 gene mutation is not a common cause of PCD, and that major or several additional disease gene(s) still remain to be identified before a sensitive molecular diagnostic test can be developed for PCD.