Highly preferential association of NonF508del CF mutations with the M470 allele.

BACKGROUND: On the basis of previous findings on random individuals, we hypothesized a preferential association of CF causing mutations with the M allele of the M470V polymorphic site of the CFTR gene. METHODS: We have determined the M/V-CF mutation haplotype in a series of 201 North East Italian and 73 Czech CF patients who were not F508del homozygotes, as F508del was already known to be fully associated with the M allele. RESULTS: Out of 358 not F508del CF genes, 84 carried the V allele and 274 the less common M allele. In the N-E Italian population, MM subjects have a risk of carrying a CF causing mutation 6.9x greater than VV subjects when F508del is excluded and 15.4x when F508del is included. In the Czech population a similar, although less pronounced, association is observed. CONCLUSIONS: Besides the possible biological significance of this association, the possibility of exploiting it for a pilot screening program has been explored in a local North East Italian population for which CF patients were characterized for their CF mutation. General M470V genotyping followed by common CF mutation screening limited to couples in which each partner carries at least one M allele would need testing only 39% of the couples, which contribute 89% of the total risk, with a cost benefit.

A new approach for identifying non-pathogenic mutations. An analysis of the cystic fibrosis transmembrane regulator gene in normal individuals.

Given q as the global frequency of the alleles causing a disease, any allele with a frequency higher than q minus the cumulative frequency of the previously known disease-causing mutations (threshold) cannot be the cause of that disease. This principle was applied to the analysis of cystic fibrosis transmembrane conductance regulator (CFTR) mutations in order to decide whether they are the cause of cystic fibrosis. A total of 191 DNA samples from random individuals from Italy, France, and Spain were investigated by DGGE (denaturing gradient gel electrophoresis) analysis of all the coding and proximal non-coding regions of the gene. The mutations detected by DGGE were identified by sequencing. The sample size was sufficient to select essentially all mutations with a frequency of at least 0.01. A total of 46 mutations was detected, 20 of which were missense mutations. Four new mutations were identified: 1341+28 C/T, 2082 C/T, L1096R, and I11131V. Thirteen mutations (125 G/C, 875+40 A/G, TTGAn, IVS8-6 5T, IVS8-6 9T, 1525-61 A/G, M470V, 2694 T/G, 3061-65 C/A, 4002 A/G, 4521 G/A, IVS8 TG10, IVS8 TG12) were classified as non-CF-causing alleles on the basis of their frequency. The remaining mutations have a cumulative frequency far exceeding q; therefore, most of them cannot be CF-causing mutations. This is the first random survey capable of detecting all the polymorphisms of the coding sequence of a gene.

Allele and haplotype frequency distribution of the EcoRI, RsaI, and MspI COL1A2 RFLPs among various human populations.

The EcoRI, RsaI, and MspI RFLPs (restriction fragment length polymorphisms) of the COL1A2 gene, one of the two genes that encode for the polypeptides of type I collagen, have been studied in four West African and two Asian populations to evaluate their potential effectiveness as anthropological markers. All three RFLPs were in Hardy-Weinberg equilibrium. The comparisons between present data on two of the major human groups and those on Europeans and Amerindians show a considerable heterogeneity for each of the three RFLPs under study. EcoRI, in particular, appears to be highly effective in distinguishing Africans, Europeans, and Asians from each other. As expected, the analysis at the haplotype level considerably improves the discriminating efficiency of these three markers by creating a clear-cut distinction between Tharus and Indonesians, the two Asian populations of the present survey. In fact, even though these two populations exhibit the same frequencies for the RsaI and MspI alleles, the frequency of the MspI(-) allele among the RsaI(-) chromosomes is 0.5 +/- 0.14 in the Indonesian sample and 0 + 0.04 in the Tharu sample.