Deletions of specific exons of FHOD3 detected by next-generation sequencing are associated with hypertrophic cardiomyopathy.

Despite new strategies, such as evaluating deep intronic variants and new genes in whole-genome-sequencing studies, the diagnostic yield of genetic testing in hypertrophic cardiomyopathy (HCM) is still around 50%. FHOD3 has emerged as a novel disease-causing gene for this phenotype, but the relevance and clinical implication of copy-number variations (CNVs) have not been determined. In this study, CNVs were evaluated using a comparative depth-of-coverage strategy by next-generation sequencing (NGS) in 5493 HCM probands and 2973 disease-controls. We detected three symmetrical deletions in FHOD3 that involved exons 15 and 16 in three HCM families (no CNVs were detected in the control group). These exons are part of the diaphanous inhibitory domain of FHOD3 protein, considered a cluster of mutations for HCM. The clinical characteristics of the affected carriers were consistent with those reported in FHOD3 in previous studies. This study highlights the importance of performing CNV analysis systematically in NGS genetic testing panels for HCM, and reinforces the relevance of the FHOD3 gene in the disease.

Clinical Relevance of the Systematic Analysis of Copy Number Variants in the Genetic Study of Cardiomyopathies.

Cardiomyopathies (CMs), one of the main causes of sudden death among the young population, are a heterogeneous group of myocardial diseases, usually with a genetic cause. Next-Generation Sequencing (NGS) has expanded the genes studied for CMs; however, the yield is still around 50%. The systematic study of Copy Number Variants (CNVs) could contribute to improving our diagnostic capacity. These alterations have already been described as responsible for cardiomyopathies in some cases; however, their impact has been rarely assessed. We analyzed the clinical significance of CNVs in cardiomyopathies by studying 11,647 affected patients, many more than those considered in previously published studies. We evaluated the yield of the systematic study of CNVs in a production context using NGS and a novel CNV detection software tool v2.0 that has demonstrated great efficacy, maximizing sensitivity and avoiding false positives. We obtained a CNV analysis yield of 0.8% that fluctuated depending on the type of cardiomyopathy studied (0.29% HCM, 1.41% DCM, 1.88% ARVC, 1.8% LVNC, 1.45% RCM), and we present the frequency of occurrence for 18 genes that agglutinate the 95 pathogenic/likely pathogenic CNVs detected. We conclude the importance of including in diagnostic tests a systematic study of these genetic alterations for the different cardiomyopathies.

Development and validation of a next-generation sequencing panel for clinical pharmacogenetics.

The rapid clinical implementation of next generation sequencing techniques is  due to its ability to sequence a large number of genetic regions at lower costs  than conventional techniques. However, its use in the field of pharmacogenetics  is still very limited. OBJECTIVE: Design, development, implementation and validation of a clinical  pharmacogenetics next-generation sequencing panel. METHOD: We developed a panel of hybrid capture probes (SureSelect®) for the  analysis of the genetic regions of clinical interest collected by literature search  and using Illumina HiSeq 1500® sequencing platform. We developed a  bioinformatic algorithm for variant annotation, haplotype inference and  determination of structural variants in the genes of interest. The results obtained were validated with Coriell® reference material from the pharmacogenetic  repositories. RESULTS: The developed panel allows the study of a total of 12,794 regions comprised in 389 genes. Validation results showed a sensitivity greater  than 99% for single nucleotide variants and small INDELs. Haplotype imputation was consistent with the consensus results in the characterized  reference materials. Furthermore, the developed tool was able to correctly  identify different types of CYP2D6 copy number variations as well as a wide  variety of HLA-B alleles. CONCLUSIONS: This technology represents an appropriate alternative for its  clinical use with advantages over conventional techniques in its throughput and  complex gene study capabilities (CYP2D6, HLA-B).

La rápida implantación clínica de las técnicas de secuenciación masiva en  paralelo se debe a su capacidad para secuenciar un gran número de regiones  genéticas con un coste menor a las técnicas convencionales. Sin embargo, su  uso en el ámbito de la farmacogenética es, todavía, muy escaso.Objetivo: Diseño, desarrollo, implementación y validación de un panel de  secuenciación masiva en paralelo de farmacogenética orientado a la práctica  clínica.Método: Se desarrolló un panel de sondas de captura híbrida (SureSelect ®)  para el análisis de las regiones genéticas de interés clínico recopiladas mediante  búsqueda bibliográfica. Se empleó la plataforma de secuenciación Illumina HiSeq 1500®. Se desarrolló un algoritmo de análisis bioinformático para la anotación  de variantes puntuales, inferencia de haplotipos y determinación de variantes  estructurales en los genes de interés. Los resultados obtenidos se validaron con  materiales de referencia Coriell® de los repositorios de farmacogenética.Resultados: El panel desarrollado permite el estudio de un total de 12.794  regiones comprendidas en 389 genes. Los resultados de validación mostraron  una sensibilidad superior al 99% para variantes puntuales e inserciones y  deleciones pequeñas. La imputación de haplotipos fue coherente con los  resultados consenso de los materiales de referencia caracterizados. Además, la  herramienta desarrollada pudo identificar correctamente diferentes tipos de  variaciones de número de copias de CYP2D6, así como una gran variedad de  alelos de HLA-B.Conclusiones: Esta tecnología representa una alternativa adecuada para su  empleo asistencial con ventajas frente a las técnicas convencionales en su  rendimiento de producción y sus capacidades de estudio de genes complejos  (CYP2D6, HLA-B).

Genetics of cardiomyopathies: novel perspectives with next generation sequencing.

Cardiomyopathies are a heterogeneous group of primary diseases of the myocardium usually of genetic origin and with familial presentation. The identification of multiple genetic causes for these diseases has opened a new window for early diagnosis, understanding of their natural history and improvement in risk stratification and management. However, in the past years, the clinical application of genetics has been limited by the prohibiting cost and restricted yield of the available genotyping technologies. The emergence of Next Generation Sequencing (NGS) has completely changed this scenario. This group of sequencing technologies allow the evaluation of hundreds or even thousands of genes in parallel at an affordable cost. Now the challenge is not genotyping per se but the interpretation of the complex results that NGS generates. In this paper we review the main aspects related to the application and impact of Next Generation Sequencing in the study of cardiomyopathies: technology, analysis procedures, bioinformatics, clinical validation and interpretation of results.