Cystic fibrosis is the most common autosomal recessive disorder in white people, with a frequency of about 1 in 2500 livebirths. Discovery of the mutated gene encoding a defective chloride channel in epithelial cells--named cystic fibrosis transmembrane conductance regulator (CFTR)--has improved our understanding of the disorder's pathophysiology and has aided diagnosis, but has shown the disease's complexity. Gene replacement therapy is still far from being used in patients with cystic fibrosis, mostly because of difficulties of targeting the appropriate cells. Life expectancy of patients with the disorder has been greatly increased over past decades because of better notions of symptomatic treatment strategies. Here, we summarise advances in understanding and treatment of cystic fibrosis, focusing on pulmonary disease, which accounts for most morbidity and deaths.

Cystic Fibrosis

The ATP-binding cassette (ABC) transporter superfamily contains membrane proteins that translocate a variety of substrates across extra- and intra-cellular membranes. Genetic variation in these genes is the cause of or contributor to a wide variety of human disorders with Mendelian and complex inheritance, including cystic fibrosis, neurological disease, retinal degeneration, cholesterol and bile transport defects, anemia, and drug response. Conservation of the ATP-binding domains of these genes has allowed the identification of new members of the superfamily based on nucleotide and protein sequence homology. Phylogenetic analysis is used to divide all 48 known ABC transporters into seven distinct subfamilies of proteins. For each gene, the precise map location on human chromosomes, expression data, and localization within the superfamily has been determined. These data allow predictions to be made as to potential functions or disease phenotypes associated with each protein. In this paper, we review the current state of knowledge on all human ABC genes in inherited disease and drug resistance. In addition, the availability of the complete Drosophila genome sequence allows the comparison of the known human ABC genes with those in the fly genome. The combined data enable an evolutionary analysis of the superfamily. Complete characterization of all ABC from the human genome and from model organisms will lead to important insights into the physiology and the molecular basis of many human disorders.

The Human ATP-Binding Cassette (ABC) Transporter Superfamily

Barrier properties of mucus.

Micro- and macrorheology of mucus.

Fertility and infertility: Definition and epidemiology.

Abnormal distribution of CF ΔF508 allele in azoospermic men with congenital aplasia of epididymis and vas deferens

To the Editor: We have previously described an increased frequency of the δF508 mutation of the cystic fibrosis gene in a group of patients with congenital absence of the vas deferens1. This sugges...

High Frequency of the R117H Cystic Fibrosis Mutation in Patients with Congenital Absence of the Vas Deferens

To assess better the link between congenital bilateral absence of the vas deferens (CBAVD) and cystic fibrosis (CF), we compared sweat chloride values, analysis of the CFTR intron 8 poly(T) tract length and analysis of 10 exons in a population of 38 patients with CBAVD. The data indicate that this population can be divided into three groups of patients. In the first group of 15 patients with abnormal sweat chloride (> 60 mmol/l), the frequency of CF mutations is high. In the second group of 18 patients with equivocal sweat chloride (between 40 and 60 mmol/l), the frequency of the 5T variant is high; 6 patients have a ΔF508 mutation and a 5T variant and 1 patient is homozygous for the 5T variant; a 5T variant has been detected in 3 other patients, and a ΔF508 mutation in another patient. A third group of 5 patients is probably not related to CF: these patients have other congenital abnormalities of the urogenital tract, low chloride values (< 40 mmol/l) and apparently no abnormality of the CF gene.

Congenital bilateral absence of the vas deferens (CBAVD) and cystic fibrosis transmembrane regulator (CFTR): correlation between genotype and phenotype

Cystic fibrosis and congenital absence of the vas deferens.

An apparently balanced reciprocal translocation 46,X,t(Y;6) (q11.23 ∼ q12;p11.1) was observed in an infertile man with severe oligozooteratozoospermia. Different mitotic chromosome banding patterns were performed and fluorescence in situ hybridization indicated a breakpoint in the fluorescent Yq heterochromatin. Molecular genetic deletion experiments for the azoospermia factor region in distal Yq11 showed the retention of the DAZ gene and meiotic pairing configurations suggested that the man’s infertility could be due to the pairing behaviour of the Y;6 translocation chromosome with the X chromosome visualised by synaptonemal complex analysis at the electron microscopy level. The morphological appearance of the normal chromosome 6 and the Y;6 translocated chromosome included in the compartment of the sex vesicle may allow an explanation of the degeneration of most spermatocytes after the pachytene stage.

Jean-Marc Rigot

Papers

Abnormal distribution of CF ΔF508 allele in azoospermic men with congenital aplasia of epididymis and vas deferens

High Frequency of the R117H Cystic Fibrosis Mutation in Patients with Congenital Absence of the Vas Deferens

Congenital bilateral absence of the vas deferens (CBAVD) and cystic fibrosis transmembrane regulator (CFTR): correlation between genotype and phenotype

Cystic fibrosis and congenital absence of the vas deferens.

Y-autosome translocation and infertility: usefulness of molecular, cytogenetic and meiotic studies.