title: Molecular and functional characterization of CBAVD-causing mutations located in CFTR nucleotide-binding domains.
abstract: BACKGROUND
  About 98% of male affected with cystic fibrosis (CF [MIM 219700]) are infertile due to bilateral absence of vas deferens (CBAVD [MIM 277180]), which makes up 1-2 % of all cases with male infertility. A previous screening of the entire coding region of the cystic fibrosis transmembrane conductance regulator gene (CFTR [MIM 602421]) in CBAVD patients identified three novel mutations: P439S is located in the first nucleotide binding domain (NBD1) of CFTR, whereas P1290S and E1401K are located in NBD2.
  
  
  METHODS
  We analysed the effects of these novel mutations on CFTR processing and chloride (Cl(-)) channel activity.
  
  
  RESULTS
  Although maturation patterns were not affected, total amounts of mature P439S-CFTR and P1290S-CFTR were reduced. Confocal microscopy showed correct membrane localisation of E1401K-CFTR, whereas P439S-CFTR and P1290S-CFTR mutants were located mainly in the cytoplasm. Iodide influx assay and whole-cell patch clamp demonstrated significantly reduced cAMP-dependent anion conductances for all three mutants.
  
  
  CONCLUSIONS
  Dysfunction of CFTR is caused by either defective CFTR trafficking (P439S and P1290S) or/and Cl- channel function (P1290S and E1401K). Thus reduced Cl- conductance caused by the three CFTR mutations affects normal development of vas deferens and leads to CBAVD, but the remaining function is sufficient to prevent other typical CF symptoms.
authors.affiliation: Department of Genetics, Faculty of Medicine, University of Porto, Portugal. anafg@med.up.pt
authors.forename: Ana
authors.initials: A
authors.lastname: Grangeia
authors.forename: René
authors.initials: R
authors.lastname: Barro-Soria
authors.forename: Filipa
authors.initials: F
authors.lastname: Carvalho
authors.forename: Ana M
authors.initials: AM
authors.lastname: Damas
authors.forename: Ana Colette
authors.initials: AC
authors.lastname: Maurício
authors.forename: Karl
authors.initials: K
authors.lastname: Kunzelmann
authors.forename: Alberto
authors.initials: A
authors.lastname: Barros
authors.forename: Mário
authors.initials: M
authors.lastname: Sousa