Analysis of CFTR mutation spectrum in Yugra region (Russian Federation)

Rapid progress in both molecular diagnostics tools and targeted therapy for cystic fibrosis (CF) requires clear understanding of CFTR mutation spectrum in population constantly living in any large region of any country. There are still no published results of comprehensive genetic study of CF patients from the Yugra region (Western Siberian part of Russia). Three-step molecular genetic approach was used for gDNA samples derived from a group of 54 CF patients living in the Yugra region: (1) AFLP/RFLP was used for the panel of 35 major CFTR mutations; (2) NGS, for full sequencing of exons and exon-intron boundaries of CFTR gene; and (3) the MLPA technique, to search for large gene rearrangements. The search of major CFTR mutations in multiethnic Yugra population accounted for only 76.6 % of all CF-causing mutations. Most common were variants F508del (rs113993960), 1677delTA (rs121908776), CFTRdele2,3, E92K (rs121908751), R1066C (rs78194216). Genomic DNA samples from 19 CF patients from the tested group in which only one mutant allele was identified were analyzed by the NGS approach followed by MLPA. This allowed to reveal 19 rare pathogenic CFTR variants, including five new variants absent in CF mutation databases. Generally, three-tier molecular genetics approach applied for the first time for a Yugra-originated cohort of CF patients allowed to find 12 missense mutations, 9 nonsense ones, 6 in/dels, 4 splice-site variants, 1 CNV. Three alleles remained unidentified. Deciphering the genetic background for CF patients living in Yugra allowed to support rational administration of CFTR modulators with profound clinical effect. The need to develop a region-specific testing panel for common CFTR mutations is demonstrated.