ABSENCE OF MUTATIONS IN THE INTERSPECIES CONSERVED REGIONS OF THE CFTR PROMOTER REGION IN CYSTIC-FIBROSIS (CF) AND CF RELATED PATIENTS

This study was aimed at testing if a 5.2 kb untranslated region on bot h sides of the first CFTR exon, shown to contain regulatory elements, could carry mutations responsible for cystic fibrosis (CF) or CF relat ed phenotypes. Selection of the DNA segments studied within this regio n was based upon the identification of conserved sequences throughout evolution (phylogenetic footprints, PFs). Comparison of the CFTR seque nces in eight species representing four orders of mammals (man, gibbon , rhesus monkey, squirrel, monkey, rabbit, cow, rat, and mouse) identi fied four clusters of PFs within the 3.9 kb of DNA sequence upstream f rom the initiation codon, as well as two nearby PFs at +1 kb within in tron 1. Six DNA segments containing PFs were scanned for mutations by denaturing gradient gel electrophoresis (DGGE) in patients with CF (n= 29), congenital bilateral absence of the vas deferens (n=143), or diss eminated bronchiectasis (n=33), for whom only one or no mutations had been identified despite extensive DGGE analysis of the 27 CFTR exons a nd exon/intron boundaries. Only one polymorphism (-966 T-->G) was iden tified with a frequency of 2.2% and no other sequence variations were found. This study reinforces the idea that the promoter region in the CFTR is not frequently mutated.