Genetic Modifiers of Cystic Fibrosis Lung Disease Severity: Whole-Genome Analysis of 7,840 Patients

Rationale: Lung disease is the major cause of morbidity and mortality in persons with cystic fibrosis (pwCF). Variability in CF lung disease has substantial non-CFTR genetic influence. Identification of genetic modifiers has prognostic and therapeutic importance. Objectives: Identify genetic modifier loci and genes/pathways associated with pulmonary disease severity. Methods: Whole genome sequencing (WGS) data on 4,248 unique pwCF with pancreatic insufficiency (PI) and lung function measures were combined with imputed genotypes from an additional 3,592 PI patients from the US, Canada, and France. This report describes association of ~15.9 million single nucleotide polymorphisms (SNPs), using the quantitative Kulich Normal Residual Mortality Adjusted (KNoRMA) lung disease phenotype in 7,840 pwCF using pre-modulator lung function data. Measurements and Main Results: Testing included common and rare SNPs, transcriptome-wide association, gene level, and pathway analyses. Pathway analyses identified novel associations with genes that have key roles in organ development, and we hypothesize these genes may relate to dysanapsis and/or variability in lung repair. Results confirmed and extended previous GWAS findings. These WGS data provide finely mapped genetic information to support mechanistic studies. No novel primary associations with common single variants or with rare variants were found. Multi-locus effects at chr5p13 (SLC9A3/CEP72) and chr11p13 (EHF/APIP) were identified. Variant effect size estimates at associated loci were consistently ordered across the cohorts, indicating possible age or birth cohort effects. Conclusions: This pre-modulator genomic, transcriptomic, and pathway association study of 7,840 pwCF will facilitate mechanistic and post-modulator genetic studies and, development of novel therapeutics for CF lung disease.