Clinical and molecular characterization of S1118F-CFTR.

Abstract

BACKGROUND:

Cystic fibrosis is a lethal autosomal recessive disorder usually associated with lung disease, pancreatic insufficiency and high sweat chloride levels.

CLINICAL CASE:

A patient admitted to Le Bonheur Children's Medical Center (LBCMC, Memphis, TN) showed symptoms of meconium ileus which required exploratory laparotomy, bowel resection and ileostomy. Genotyping showed DeltaF508/I1027T on one chromosome and S1118F on the other. Sweat testing on three different occasions gave negative and intermediate results (22.7, 24.6 mmol/L; 55.1, 58.6 mmol/L and 55.1, 58 mmol/L) and pancreatic elastase testing showed normal levels.

OBJECTIVE:

To characterize S1118F-CFTR mutation at a molecular level to help understand the associated CF-phenotype.

METHODS:

Molecular characterization of S1118F-CFTR mutant was studied in HEK-293 cells at 37 degrees C. Various biochemical methods such as Western blotting, real-time PCR, Pulse chase labeling and iodide efflux assay were employed.

RESULTS:

S1118F-CFTR makes less than 10-15% of mature CFTR (band C) compared to WT-CFTR. The mRNA levels of S1118F-CFTR and WT-CFTR are comparable. S1118F-CFTR is functional but shows about 10-15% of WT-CFTR activity. S1118F-CFTR shows impaired maturation and CF-correctors can increase the amount of mature and functional CFTR by three- to fourfold.

CONCLUSION:

S1118F-CFTR shows impaired maturation and an individual with S1118F-CFTR paired with DeltaF508-CFTR exhibits atypical CF symptoms with intermediate sweat chloride level and meconium ileus despite documented pancreatic sufficiency.

• Authors: Himabindu Penmatsa, Carla A Frederick, Sunitha Nekkalapu, Veronica G Conoley, Weiqiang Zhang, Chunying Li, John Kappes, Dennis C Stokes, Anjaparavanda P Naren
• Journal: Pediatric pulmonology (Pediatr Pulmonol) Vol. 44 Issue 10 Pg. 1003-9 (Oct 2009) ISSN: 1099-0496 [Electronic] United States
• PMID: 19774621 (Publication Type: Case Reports, Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Chlorides
• cystic fibrosis transmembrane conductance regulator delta F508
• Cystic Fibrosis Transmembrane Conductance Regulator
• RNA

Topics

• Blotting, Western
• Cells, Cultured
• Chlorides (analysis)
• Cystic Fibrosis (genetics)
• Cystic Fibrosis Transmembrane Conductance Regulator (genetics)
• Exocrine Pancreatic Insufficiency (genetics)
• Female
• Genetic Predisposition to Disease
• Genetic Variation
• Genotype
• Humans
• Ileus (genetics)
• Male
• Mutation
• Phenotype
• Probability
• RNA (analysis)
• Reverse Transcriptase Polymerase Chain Reaction
• Sweat (chemistry, metabolism)