Mutational screening in Italian patients with primary ciliary dyskinesia by next-generation sequencing (NGS)

Abstract

Primary Ciliary Dyskinesia (PCD) is a rare genetic disorder that causes deficiency in mucociliary clearance, with consequent chronic disease of upper and lower airways. Currently, the diagnosis of PCD relies on cilium morphology, motility and ultrastructure, nasal nitric oxide measurement and genetic analysis. The latter is hampered by the high heterogeneity of the disease, as autosomal recessive causative mutations have been found in 33 different genes. In this study we clinically and molecularly characterized the first cohort of Italian PCD patients (44 probands) in order to gain insight into genes, mutations and associated clinical phenotypes. Genetic analysis has been performed by developing a custom NGS panel (Ion Torrent™ platform) for the simultaneous screening of the most frequently mutated PCD genes. For each subject we identified about 300 sequence variants that were filtered on the basis of frequency and functional annotation. Overall we found 5 homozygous and 14 compound heterozygous mutations, 21 of which were novel, reaching a molecular diagnosis rate of 43%. Our study highlights several issues relevant to the molecular diagnosis of PCD: i) the definition of mutation pathogenicity based on database data should be integrated with comprehensive segregation analyses and/or functional studies; ii) the identification of a single damaging DNA variant in 6 patients suggests the need of novel strategies to detect unconventional pathogenic mutations; iii) mutation frequencies confirm DNAH5 and DNAH11 as the most common causes of PCD also in Italy but some population specificities as well as founder or mutational hot spots have been identified. (RF-VEN-2008-1201767).