[Cystic fibrosis: molecular genetics and new perspectives of prevention and therapy]. / Fibrosi cistica: genetica molecolare e nuove prospettive di prevenzione e terapia.

Cystic fibrosis (CF) is the most common lethal autosomal recessive disorder among Caucasians, occurring with a frequency of 1/2000 newborn babies. This editorial will consider the clinical features of CF as well as the genomic structure of the CFTR gene and the functional properties of its product, mutations of the gene, correlations between genotypes and phenotypes, strategies for carrier screening, and recent advances in gene therapy. After isolation and cloning of the CFTR gene, different laboratories have characterized over 350 mutations responsible for CF, the most frequent being the delta F508 which accounts for 70% of all CF chromosomes. Studies on correlations between genotypes and phenotypes have confirmed that patients with the homozygous delta F508/delta F508 genotype are severely affected, with major involvement of pancreatic function. Patients with the delta F508/R117H genotype, on the other hand, evidence a mild phenotype with pancreatic sufficiency. Several pilot studies for carrier detection are now in progress. As recent experiments with somatic gene therapy, performed on knock-out mice for the CFTR gene have given satisfactory results, it is hoped that the same approach can soon be used for humans.

Analysis of CA/GT microsatellite polymorphism in IVS8 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene: a study of Italian CF families.

Forty-six CF Italian patients and their parents were screened for a highly polymorphic microsatellite consisting of a variable number of CA/GT repeats in intron 8 of the CFTR gene. A strong degree of association was found between alleles 2 and 6 and the CF mutation delta F508. Moreover, considering the haplotypes at the closely linked locus D7S23 and the microsatellite's alleles, a strong linkage disequilibrium was again found for delta F508 and also for non-delta F508 CF chromosomes and the eight commonest haplotypes (B2, B6, C7, A6, A7, B7, D2 and D7). These data, compared with those described in the Spanish population, further support the common origin of the delta F508 mutation in Southern European populations.

delta F508 deletion in cystic fibrosis in Italian families.

In 20 Italian families with cystic fibrosis (CF), restriction fragment length polymorphisms were detected by five linked markers; a strong linkage disequilibrium is observed between the haplotype B (alleles 2/1 with respect to KM19/XV2c) and CF. The frequency of the delta F508 deletion in CF chromosomes of this sample is 50%. A significant correlation is found between the absence of the delta F508 mutation and pancreatic sufficiency.

Carrier detection for prenatal diagnosis of hemophilia A in Italian families.

BACKGROUND: The results obtained from a comparative analysis between phenotypic bioassays as the ratio of factor VIII: C clotting activity to factor VIII: C-related antigen, and DNA haplotypes from RFLP's TaqI/St14 and BclI/F8A in 12 hemophilia A (HeA) families are described. METHODS: DNA from HeA patients and related at-risk women has been analyzed by Southern blotting with two probes: the intragenic F8A and the extragenic St14. Factor VIII: C coagulant activity was measured by a one-stage method, and the Factor VIII-related antigen (FVIII: RAg) was assayed with bidimensional electrophoresis. Linkage analysis was performed with the LINKAGE computer programs; in particular, the risks of carrying HeA were calculated using the MLINK program. RESULTS: The observed heterozygosity for the flanking marker DXS 52 (TaqI/St14 RFLP) in combination with intragenic BclI/F8A polymorphism was 0.94. A statistically significant difference in frequency was detected at the DXS 52 locus (allele 4) in comparison with other Caucasian populations. Linkage analysis made it possible to combine the plasma bioassay values with the DNA marker haplotypes to determine the probability of carriership; 22 females at risk were investigated: 4 of them were identified as carriers and 18 were excluded. The risk of carrying hemophilia A for some women at risk in six families is reported. CONCLUSIONS: This study compares a classic method and DNA analysis in genetic counselling for hemophilia A. In some cases the two methods may give different results when identifying carriers in at-risk families. From these data it is possible to conclude that DNA analysis combined with the phenotypic bioassays for carrier detection gives more information that the two analyses taken separately.

Congenital bilateral absence of vas deferens with a new missense mutation (P499A) in the CFTR gene.

We describe a congenital bilateral absence of the vas deferens (CBAVD) patient with a compound heterozygosity in the cystic fibrosis transmembrane regulator (CFTR) gene for a stop mutation W1282X and a new missense mutation P499A. The P499A is interpreted as a mild mutation whose phenotypic effects, in this case limited to the development of wolffian duct derivatives, are revealed only in combination with a severe CFTR mutation.

Polyvariant mutant CFTR genes in patients with chronic pancreatitis.

Several authors have reported an association between mutations of the cystic fibrosis transmembrane conductance regulator gene (CFTR) and chronic pancreatitis. CFTR gene transcription and protein efficiency are influenced by two polymorphic loci, (TG)m and M470V, other than the T5 allele, whose role is already well-established. The TG11/T5 haplotype is commonly found in healthy subjects, while the TG12/T5/V470 and TG13/T5/V470 haplotypes are present in congenital bilateral absence of the vas deferens (CBAVD) patients. While the T5 allele is a mutation that is over-represented in patients with chronic pancreatitis, no data are available concerning the possible allelic preference at the other two polymorphic loci, (TG)m and M470V, in these patients. For this reason, we screened 39 patients with chronic pancreatitis for the most common CFTR mutations found so far in the Italian population; in addition, we examined the length of the polypyrimidine (poly-T) tract in intron 8, the (TG)m length and the M or V codon at position 470. CFTR mutations were found in 3 patients. Poly-T variant typing identified genotype T5/T7 in 5 patients and T5/T9 in 1 patient. Direct sequencing of intron 8 in patients with the T5 variant revealed the TG12/T5/V470//TG11/T7/V470 genotype in 5 patients and TG10/T9//TG11,T5 genotype in 1 patient. In patients with chronic pancreatitis, the T5 allele is frequently associated with TG12 and V470, a haplotype already reported in CBAVD cases and quite uncommon in healthy subjects.