Dysfunctions of the Cystic Fibrosis Transmembrane conductance regulator (CFTR) gene are responsible for the highly variable clinical presentation ranging from severe Cystic Fibrosis to male infertility due to congenital bilateral absence of the vas deferens (CBAVD). Despite extensive scanning, a small proportion of the CFTR mutations remains unidentified. We performed the functional analyses of a promoter sequence variation and 4-bp repeats in intron 9 identified in CBAVD patients. Results show that these variants significantly perturb the CFTR transcription and the binding affinity for the FOX proteins. Our findings strengthen the importance to search uncommon variants in the CFTR non-coding regions. (By Dr. Magali Taulan, http://jmg.bmj.com/content/early/2010/10/23/jmg.2010.081851.abstract?papetoc)