A novel donor splice site characterized by CFTR mRNA analysis induces a new pseudo-exon in CF patients

Background: The CFTR gene is tightly regulated and differentially expressed in many mucosal epithelial cell types. There is evidence of an increasing number of genomic variations in the intronic regions influencing mRNA splicing, and also the level of normal CFTR transcript. Methods: In the present study, we investigate the molecular defect by RT-PCR analyzing the mRNA of 25 cystic fibrosis (CF) patients in whom only one or no CF allele had been identified after DNA analysis (of all the exons of the CFTR gene). Results: mRNA analysis led to the detection of a cryptic exon in two patients: the new exon is a 104. bp insertion between exons 10 and 11 and is caused by a new point mutation c.1584. +. 18672. bp A. >G (http://www.hgvs.org/mutnomen/) discovered in intron 10; moreover, they showed the absence of exon 9 skipping. Conclusions: Our results confirm the utility of RNA analysis in discovering new mutations and in investigating their effect on normal splicing processes.