CFTR mutation analysis and haplotype associations in CF patients

Area of Science:

• Genetics
• Molecular Biology
• Public Health

Background:

• Newborn screening (NBS) laboratories commonly employ second-tier molecular tests for cystic fibrosis (CF) using dried blood spots (DBS).
• The Centers for Disease Control and Prevention (CDC) provides proficiency testing (PT) for CF transmembrane conductance regulator (CFTR) gene mutation detection in DBS.
• Accurate molecular characterization is crucial for quality assurance in CF newborn screening.

Purpose of the Study:

• To perform extensive molecular characterization of the CFTR gene in a U.S. population cohort.
• To identify and verify CF-associated mutations and sequence variations.
• To understand the haplotype background of CF mutations for improved genotype-phenotype studies and mutation phasing.

Main Methods:

• Comprehensive sequencing of coding regions, regulatory regions, and introns of the CFTR gene.
• Characterization of large insertions/deletions and intronic di-nucleotide microsatellites.
• Haplotype prediction using HapMap data for variants within a major haplotype block.

Main Results:

• Molecular characterization of 76 individuals (CF patients, family members, screen-positive newborns).
• Identification and verification of at least two mutations in CF patient samples, with four specimens containing three likely CF-associated mutations.
• Discovery of 34 sequence variations, including five novel variants, and prediction of haplotypes, revealing a common haplotype subgroup for F508del, G542X, and N1303K mutations.

Conclusions:

• The identified haplotype background of CF-associated mutations in the U.S. population provides a framework for future studies.
• This understanding will assist in determining the cis/trans phase of mutations without requiring parental studies.
• Enhanced molecular characterization supports improved accuracy and interpretation of cystic fibrosis newborn screening results.