Copy number variation in DRC1 is the major cause of primary ciliary dyskinesia in the Japanese population
Primary ciliary dyskinesia (PCD) is a rare genetic disorder caused by functional impairment of cilia throughout the body. The involvement of copy number variation (CNV) in the development of PCD is largely unknown. We examined 93 Japanese patients with clinically suspected PCD from 84 unrelated families. CNV was examined either by exome sequencing of a PCD gene panel or by whole-exome sequencing (WES). The identified alterations were validated by PCR and Sanger sequencing. Nasal ciliary ultrastructure was examined by electron microscopy. Analysis of CNV by the panel or WES revealed a biallelic deletion in the dynein regulatory complex subunit 1 (DRC1) gene in 21 patients, which accounted for 49% of the PCD patients in whom a disease-causing gene was found. Sanger sequencing of the PCR product revealed a 27,748-bp biallelic deletion including exons 1-4 of DRC1 with identical breakpoints in all 21 patients. The ciliary ultrastructure of the patients with this CNV showed axonemal disorganization and the loss or gain of central microtubules. The deletion of DRC1 is the major cause of PCD in Japan and this alteration can cause various ciliary ultrastructural abnormalities.