Combining RSPH9 founder mutation screening and next-generation sequencing analysis is efficient for primary ciliary dyskinesia diagnosis in Saudi patients

Abstract

Primary ciliary dyskinesia (PCD) is a clinically and genetically heterogeneous ciliopathy. Dysfunction of motile respiratory and nodal cilia results in sinopulmonary symptoms associated with laterality defects (LD) found in half of the patients. The molecular basis of the disease is insufficiently investigated in patients originating from the Arabian Peninsula. In a group of 16 unrelated Saudi patients clinically suspected of PCD and among whom only 5 (31%) had LD, we first screened by PCR-RFLP two founder mutations, RSPH9 c.804_806del and CCDC39 c.2190del previously identified in patients from the Arabian Peninsula and Tunisia, respectively. When negative, targeted panel or whole-exome sequencing was performed. Three patients were homozygous for the mutation in RSPH9, which encodes an axonemal protein that is absent from nodal cilia. None of the patients carried the CCDC39 founder mutation frequent in Tunisia. NGS analysis showed that nine patients had homozygous mutations in PCD genes. In total, sequential RFLP and NGS analysis solved 75% (12/16) of cases and identified ten distinct mutations, among which six are novel, in nine different genes. These results, which highlight the genetic heterogeneity of PCD in Saudi Arabia, show that the RSPH9 c.804_806del mutation is a prevalent mutation among Saudi patients, whereas the CCDC39 c.2190del ancestral allele is most likely related to the Berber population. This study shows that RSPH9 founder mutation first-line screening and NGS analysis is efficient for the genetic exploration of PCD in Saudi patients. The RSPH9 founder mutation accounts for the low rate of LD among Saudi patients.