Variants in CFTR untranslated regions are associated with congenital bilateral absence of the vas deferens.
BACKGROUND
Congenital bilateral absence of the vas deferens (CBAVD), a frequent cause of obstructive azoospermia, is generated by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Despite extensive testing for point mutations and large rearrangements, a small proportion of alleles still remains unidentified in CBAVD patients.


RESULTS
Mutation scanning analysis of microsatellite variability in the CFTR gene identified two undescribed 4 bp sequence repeats (TAAA)(6) and (TAAA)(8) in intron 9 in two CBAVD patients heterozygote for either the -33G→A promoter transition or the classical [TG12T5] CBAVD mutation. This study explores the putative impact of this promoter variant by using a combination of web based prediction tools, reporter gene assays, and DNA/proteins interaction analyses. Results of transiently transfected vas deferens cells with either the -33G wild-type or the -33A variant CFTR directed luciferase reporter gene confirmed that the -33A variant, which alters the FOXI1 (Forkhead box I1) binding, significantly decreases the CFTR promoter activity. It was also investigated whether regulatory elements located within the intronic tetrarepeat might influence the CFTR expression. There was evidence that both the (TAAA)(6) and the (TAAA)(8) alleles modulate the CFTR transcription and the binding affinity for FOX transcription factors, involved in the chromatin architecture.


CONCLUSIONS
As the vas deferens seems to be one of the tissues most susceptible to a reduction in the normal CFTR transcripts levels, and as two mild mutations are sufficient to induce CBAVD phenotype, these findings raise the possibility that these uncommon variants may be a novel cause of CBAVD.
Université Montpellier1, UFR de Médecine, Montpellier, France.
Estelle
E
Lopez
Victoria
V
Viart
Caroline
C
Guittard
Carine
C
Templin
Céline
C
René
Déborah
D
Méchin
Marie
M
Des Georges
Mireille
M
Claustres
Marie-Catherine
MC
Romey-Chatelain
Magali
M
Taulan
D000483:Alleles; D002478:Cells, Cultured; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D004252:DNA Mutational Analysis; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006579:Heterozygote; D006801:Humans; D007248:Infertility, Male / Q000235:genetics*; D007438:Introns; D008297:Male; D018895:Microsatellite Repeats; D009154:Mutation; D010641:Phenotype; D011401:Promoter Regions, Genetic; D020506:Untranslated Regions; D014649:Vas Deferens / Q000002:abnormalities*
C505032:CFTR protein, human; C477894:FOXI1 protein, human; D051858:Forkhead Transcription Factors; D020506:Untranslated Regions; D019005:Cystic Fibrosis Transmembrane Conductance Regulator