Liver expression in cystic fibrosis could be modulated by genetic factors different from the cystic fibrosis transmembrane regulator genotype.

During a multicentric study conducted in Southern Italy, we studied five sets of cystic fibrosis siblings bearing a strongly discordant liver phenotype, three with genotype DeltaF508/R553X, one with genotype DeltaF508/unknown, and one with genotype unknown/unknown. The siblings of each set were raised in the same family environment, and there were no interpair differences in nutritional state or in therapy compliance. All siblings had pancreatic insufficiency and moderate respiratory expression. One sibling of each of the five sets was free of liver involvement, and the other had severe liver expression. Other causes of liver disease (viral, metabolic, and genetic other than cystic fibrosis) were ruled out. Therefore, environmental factors, nutritional state, and therapy compliance are not involved in the liver expression of cystic fibrosis in the five unrelated sibships. This suggests that modifier genes, inherited independently of the cystic fibrosis transmembrane regulator gene, could modulate the liver expression in cystic fibrosis patients.

Prenatal diagnosis of cystic fibrosis: a case of twin pregnancy diagnosis and a review of 5 years' experience.

We performed prenatal diagnoses for cystic fibrosis in 32 high risk (1:4) couples (including a dizygotic pregnancy). Chorionic villi sampling did not cause abortion or fetal malformation in any case. The preliminary analysis of 9 short tandem repeats always excluded maternal contamination of the DNA extracted from chorionic villi and confirmed paternity. Twenty-two prenatal diagnoses were made by direct analysis of the mutations. In seven cases diagnosis was made by the analysis of intragenic polymorphisms; in three cases, we analyzed two extragenic polymorphisms. The prenatal diagnosis (including genetic counselling) was completed within 24 h from the sampling. Seven prenatal diagnoses revealed an affected fetus; all couples opted for therapeutic abortion. In 17 cases the fetus was heterozygote, and in seven cases it was non carrier of mutated alleles. In the twin pregnancy, mutations were DeltaF508/N1303K. Direct analysis of the DNA extracted from the two independent samples of chorionic villi revealed one fetus non carrier of mutated alleles and the other a carrier of the N1303K mutation. Analysis of the HPRT locus predicted both the fetuses as males. Furthermore, the genotype of each fetus was defined after birth. The prenatal diagnosis with chorionic villi sampling plays a key role in the prevention of cystic fibrosis. The laboratories must be equipped for both the direct analysis of mutations and for the analysis of a large number of polymorphisms. The preliminary analysis of short tandem repeats is recommended both to exclude maternal contamination and to confirm parentage.

Detection of five rare cystic fibrosis mutations peculiar to Southern Italy: implications in screening for the disease and phenotype characterization for patients with homozygote mutations.

BACKGROUND: The search for the eight most frequent mutations (i.e., DeltaF508, G542X, W1282X, N1303K, 1717-1G-->A, R553X, 2183AA-->G, and I148T) by allele-specific oligonucleotide dot-blot analysis revealed 78% of 396 cystic fibrosis alleles in Southern Italy. The observation of frequent haplotypes on the unidentified cystic fibrosis alleles suggested that a few mutations could account for a large number of unidentified alleles. METHODS: We screened most of the coding sequence of the cystic fibrosis transmembrane regulator gene by denaturing gradient gel electrophoresis to determine the spectrum of these mutations in 68 unrelated cystic fibrosis patients bearing one or both unidentified mutations. RESULTS: The screening revealed five mutations, R1158X, 711+1G-->T, 4016insT, L1065P, and G1244E, each of which had a frequency of 1.3-1.8% (7% collectively). The 7% increase in the detection rate (85% vs 78%) reduces by >50% the residual risk of being cystic fibrosis carriers for couples who had tested negative by molecular analysis. We therefore designed a second allele-specific oligonucleotide set to analyze the five mutations. Among the patients analyzed, one patient homozygous for the L1065P mutation expressed a mild pulmonary and intestinal form of the disease with pancreatic insufficiency. Two other patients, homozygous for mutations R1158X and 4016insT, both expressed a severe cystic fibrosis phenotype. CONCLUSIONS: Five cystic fibrosis mutations are peculiar to patients from Southern Italy. The method described for their analysis is efficient, inexpensive, and can be semi-automated by use of a robotic workstation. The results obtained in patients from Southern Italy may have an impact on laboratories in other countries, given the large migrations of populations from Southern Italy to other countries in the last two centuries.

Lactase persistence versus decline in human adults: multifactorial events are involved in down-regulation after weaning.

BACKGROUND & AIMS: In nonhuman mammals, lactase activity declines during or after weaning. In contrast, about one half of the human species maintains high lactase activity even in adulthood. To clarify this difference, this study examined some parameters for which contrasting observations have been reported in connection with lactase decline. METHODS: Lactase activity, lactase messenger RNA (mRNA) levels, and in vitro lactase biosynthesis were determined in normal jejunal samples from a large group of white adults, all born in or near Naples. RESULTS: Of 44 individuals, 10 were lactase persistent and 34 were hypolactasic. Biosynthesis of prolactase correlated well with lactase mRNA levels, indicating transcriptional control; it did less so with steady-state lactase activity. Examination of lactase mRNA levels and lactase activity/lactase mRNA ratios revealed a heterogeneous pattern of lactase mRNA level, lactase synthesis, and activity in both lactase persistent and hypolactasic subjects. CONCLUSIONS: Both transcriptional and posttranscriptional factors cause the decline of intestinal lactase. This probably explains the multifarious observations that most studies on adult-type hypolactasia have reported. The single overriding factor distinguishing lactase-persistent subjects from hypolactasic subjects is the high rate of lactase biosynthesis.