First Joint Meeting BeSHG / NVHG location:Leuven date:4-5 February 2016
Cardiomyopathies (CMP) and primary arrhythmia syndromes (PAS) are characterized by a
significant genetic heterogeneity, rendering classical sequencing expensive and very
laborious. As a proof of concept, we evaluated targeted massive parallel sequencing (MPS)
as a fast and efficient diagnostic method.
An in-solution NimbleGen SeqCap EZ capture was designed in order to capture the coding
region of 75 genes associated with arrhythmias and cardiomyopathies. The probe design
covers approximately 850 kb of genomic sequence, corresponding to 94% of the targeted
region. Targeted sequencing was performed on the Illumina Hiseq 2500 platform as 150bp
paired-end reads. Variant annotation and classification into 5 classes was achieved according
to a stringent scoring system, taking into account different in silico analyses, population
frequencies, paralogous/orthologous conservation and supportive literature.
From January 2014 till June 2015, 532 patients suspected of CMP or PAS were screened with
targeted sequencing. In total, 25% and 18% had a pathogenic mutation in a gene related to
CMP or PAS respectively. In addition, 27% and 17% showed variants of unknown significance
(VUS) for CMP or PAS. For patients carrying a VUS, segregation analysis will be performed
(if possible) in order to elucidate their role.
Our results show that targeted sequencing for CMP and PAS works as an efficient and costeffective
tool for genetic diagnosis of these heterogeneous disorders in a diagnostic setting.
The mutations are mostly located in the so-called ‘core genes’, indicating that the extra yield
of additional genes is limited. The lower yield of ‘solved’ cases in comparison with the
literature is mainly due to the fact that genetic testing for CMP or PAS is easy accessible for
medical specialists in Belgium. Given the huge amount of information generated by MPS, a
rigorous filtering strategy of variants together with multidisciplinary collaboration is crucial to
determine the potential pathogenic role of identified variants in the cause of CMP and PAS.