The epithelial sodium channel is a modifier of the long-term nonprogressive phenotype associated with F508del CFTR mutations

Pankaj B. Agrawal, Ruobing Wang, Hongmei Lisa Li, Klaus Schmitz-Abe, Chantelle Simone-Roach, Jingxin Chen, Jiahai Shi, Tin Louie, Shaohu Sheng, Meghan C. Towne, Christine F. Brainson, Michael A. Matthay, Carla F. Kim, Michael Bamshad, Mary J. Emond, Norma P. Gerard, Thomas R. Kleyman, Craig Gerard

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Cystic fibrosis (CF) remains the most lethal genetic disease in the Caucasian population. However, there is great variability in clinical phenotypes and survival times, even among patients harboring the same genotype. We identified five patients with CF and a homozygous F508del mutation in the CFTR gene who were in their fifth or sixth decade of life and had shown minimal changes in lung function over a longitudinal period of more than 20 years. Because of the rarity of this long-term nonprogressive phenotype, we hypothesized these individuals may carry rare genetic variants in modifier genes that ameliorate disease severity. Individuals at the extremes of survival time and lung-function trajectory underwent whole-exome sequencing, and the sequencing data were filtered to include rare missense, stopgain, indel, and splicing variants present with a mean allele frequency of ,0.2% in general population databases. Epithelial sodium channel (ENaC) mutants were generated via site-directed mutagenesis and expressed for Xenopus oocyte assays. Four of the five individuals carried extremely rare or never reported variants in the SCNN1D and SCNN1B genes of the ENaC. Separately, an independently enriched rare variant in SCNN1D was identified in the Exome Variant Server database associated with a milder pulmonary disease phenotype. Functional analysis using Xenopus oocytes revealed that two of the three variants in d-ENaC encoded by SCNN1D exhibited hypomorphic channel activity. Our data suggest a potential role for d-ENaC in controlling sodium reabsorption in the airways, and advance the plausibility of ENaC as a therapeutic target in CF.

Original languageEnglish
Pages (from-to)711-720
Number of pages10
JournalAmerican Journal of Respiratory Cell and Molecular Biology
Issue number6
StatePublished - Dec 2017

Bibliographical note

Publisher Copyright:
Copyright © 2017 by the American Thoracic Society.


  • Cystic fibrosis
  • ENaC
  • Epithelial sodium channel
  • Genetic modifier
  • SCNN1D

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry
  • Cell Biology


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