In monosymptomatic forms of cystic fibrosis such as congenital bilateral absence of vas deferens, variations in the TG m and T n polymorphic repeats at the 3 end of intron 8 of the cystic fibrosis transmembrane regulator (CFTR) gene are associated with the alternative splicing of exon 9, which results in a nonfunctional CFTR protein. Using a minigene model system, we have previously shown a direct relationship between the TG m T n polymorphism and exon 9 splicing. We have now evaluated the role of splicing factors in the regulation of the alternative splicing of this exon. Serine-arginine-rich proteins and the heterogeneous nuclear ribonucleoprotein A1 induced exon skipping in the human gene but not in its mouse counterpart. The effect of these proteins on exon 9 exclusion was strictly dependent on the composition of the TG m and T n polymorphic repeats. The comparative and functional analysis of the human and mouse CFTR genes showed that a region of about 150 nucleotides, present only in the human intron 9, mediates the exon 9 splicing inhibition in association with exonic regulatory elements. This region, defined as the CFTR exon 9 intronic splicing silencer, is a target for serine-arginine-rich protein interactions. Thus, the nonevolutionary conserved CFTR exon 9 alternative splicing is modulated by the TG m and T n polymorphism at the 3 splice region, enhancer and silencer exonic elements, and the intronic splicing silencer in the proximal 5 intronic region. Tissue levels and individual variability of splicing factors would determine the penetrance of the TG m T n locus in monosymptomatic forms of cystic fibrosis. Cystic fibrosis (CF),1 the most common life-shortening autosomal recessive disorder in Caucasians, is caused by mutations in the CF transmembrane regulator (CFTR) gene and is characterized by pathological features of variable severity at the level of lungs, pancreas, sweat glands, testis, ovaries, and intestine (1). Monosymptomatic forms of the disease such as congenital bilateral absence of vas deference (CBAVD), pancreatitis, nasal polyposis, disseminated bronchiectasies, and broncopulmonary allergic aspergillosis frequently present a peculiar allele at the polymorphic CFTR intron 8-exon 9 junction (2-8). At this locus a variable number of dinucleotide TG repeats (from 9 to 13) followed by a T repeat (T5, T7, or T9) can be found in the normal population, and it has been suggested that the T5 allele is a disease mutation with incomplete penetrance that could be modulated by the simultaneous presence of other mutations and/or polymorphisms (3). The pathologic effect of the T5 allele has been associated to the alternative splicing of the CFTR exon 9, which is extremely variable in humans among different individuals (9). Interestingly, exon 9 skipping is absent in mouse, and it has been reported not to be evolutionary conserved (10). This exon encodes part of the functionally important first nucleotide-binding domain, and its skipping produces a nonfunctional CFTR protein (10, 11). In CBAVD patients ...

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The benefits of early treatment of nutritional and respiratory problems in the CF infant and of genetic counselling for the parents are widely recognized. However, clinical diagnosis of CF is often delayed despite early onset of symptoms and the usefulness of neonatal population screening as a preventive measure is still under debate. This study analyses the clinical history of CF patients diagnosed exclusively on the basis of positive neonatal screening tests with the aim of identifying the earliest markers of the disease. We studied 103 CF infants born in north-east Italy, diagnosed following neonatal screening: assay of immunoreactive trypsin (IRT) from a heel-prick blood sample followed by a measurement of meconium lactase in cases with raised IRT. Diagnosis was confirmed by sweat test at an average age of 39 days. Eighty-one patients (79%) had symptoms strongly suggestive of CF at diagnosis, and signs and/or symptoms of pancreatic insufficiency were present in 16 of the remaining 22 cases. The most frequent symptom was growth failure (69% of infants) and of these, 44% weighed the same as at birth or less. Pancreatic insufficiency was confirmed by the low level of faecal chymotrypsin found in 85% of cases. IRT was elevated in all cases. CF had not been suspected in any symptomatic infant, although most of the infants had been monitored by a paediatrician. In conclusion, most infants with CF diagnosed by neonatal screening are already symptomatic in the first six weeks of life and the most frequent symptom is failure to thrive; pancreatic insufficiency was already present in most cases. In areas without CF neonatal screening programs, the disease should be excluded by differential diagnosis in all cases with growth failure notwithstanding adequate caloric intake in the first months of life. The high sensitivity, low cost and simple execution of IRT and fecal chymotrypsin tests make them an ideal first step in suspect cases before proceeding to the sweat test, often performed late because of limited availability.

We performed MBL2 genotyping in 47 CF patients-cared of at the regional CF Centre of Trieste-trying to establish a correlation within allelic variants of MBL2 and modification of patients' clinical outcome. FEV1 values were significantly lowered and a significantly earlier age at onset of Pseudomonas aeruginosa colonisation was found in CF patients with at least one MBL2 variant.

Evidence was found that antibiotic treatment can reduce the rate of positive cultures and of anti-PA antibody titres in asymptomatic CF patients with newly isolated PA. Different therapeutic options have not been directly compared: a multi-centre comparative study needs to be carried out.