Gene Mutation in MicroRNA Target Sites of CFTR Gene: A Novel Pathogenetic Mechanism in Cystic Fibrosis?

Abstract

Cystic fibrosis (CF) is the most frequent lethal genetic disorder among Caucasians. It depends on alterations of a chloride channel expressed by most epithelial cells and encoded by CFTR gene. Also using scanning techniques to analyze the whole coding regions of CFTR gene, mutations are not identified in up to 10% of CF alleles, and such figure increases in CFTR-related disorders (CFTR-RD). Other gene regions may be the site of causing-disease mutations. We searched for genetic variants in the 1500 bp of CFTR 3′ untranslated region, typical target of microRNA (miRNA) posttranscriptional gene regulation, in either CF patients with the F508del homozygous genotype and different clinical expression (n = 20), CF (n = 32) and CFTR-RD (n = 43) patients with one or none mutation after CFTR scanning and in controls (n = 50). We identified three SNPs, one of which, the c.*1043A>C, was located in a region predicted to bind miR-433 and miR-509-3p. Such mutation was peculiar of a CFTR-RD patient that had Congenital Bilateral Absence of Vas Deferens (CBAVD), diffuse bronchiectasis, a borderline sweat chloride test and the heterozygous severe F508del mutation on the other allele. The expression analysis demonstrated that the c.*1043A>C increases the affinity for miR-509-3p and slightly decreases that for the miR-433. Both miRNAs cause in vitro a reduced expression of CFTR protein. Thus, the c.*1043A>C may act as a mild CFTR mutation enhancing the affinity for inhibitory miRNAs as a novel pathogenetic mechanism in CF.

Developmental control of CFTR: from bioinformatics to novel therapeutic approaches

“…This report adds significantly to our existing knowledge regarding miRNA regulation of CFTR [5- 10,13] and the developing field of miR-based CFTR therapeutics [15]. The data confirms previous studies implicating miR-145 and miR-101 as important modulators of CFTR expression [5,6,8,9] and build on them by demonstrating how MBBOs based on these miRNAs can affect CFTR gene expression and CFTR protein function.…”

The role of microRNAs in chronic respiratory disease: recent insights

“…Some discrepancy has arisen on the role of miR-101, as this miRNA targeted the CFTR 3′ UTR in some studies, but not in others (Gillen et al, 2011;Megiorni et al, 2011;Hassan et al, 2012). In addition, CF-causing mutations were identified in the 3′ UTR of CFTR, one of which (1043A → C) was recently found to alter the affinity of miR-433 and miR-509, suggesting these miRNAs to also have disease relevance (Amato et al, 2013).…”

Genotype–phenotype correlation and functional studies in patients with cystic fibrosis bearing CFTR complex alleles

“…Moreover, an increasing number of patients is diagnosed as CFTR-related disorders (CFTR-RD)2 generally characterised by a later onset of symptoms involving a single organ (ie, pancreatitis, disseminated bronchiectasis, obstructive azoospermia secondary to congenital bilateral absence of vas deferens (CBAVD)),3 usually associated to borderline SCL and mutations causing a different degree of CFTR protein dysfunction either in coding4–6 and in non-coding CFTR gene regions 7 8. Finally, the growing proportion of newborn screening (NBS) programmes revealed a large number of infants having a Cystic Fibrosis Screen Positive, Inconclusive Diagnosis (CFSPID) including those infants with discordance between immunoreactive trypsinogen at the NBS, SCL, CFTR genotype and clinical phenotype 9 10…”