Mutational screening of the cationic trypsinogen gene in a large cohort of subjects with idiopathic chronic pancreatitis

Several missense mutations, including R122H, N29I, K23R, A16V and D22G, in the cationic trypsinogen gene (PRSS1), have been associated with certain forms of hereditary pancreatitis (HP). Their occurrence in the idiopathic chronic pancreatitis (ICP) and whether novel mutations could be identified in PRSS1 remain to be further evaluated. These were addressed by the mutational screening of the entire coding sequence and the intronic/exonic boundaries of the PRSS1 gene in 221 ICP subjects, using a previously established denaturing gradient gel electrophoresis technique. Among the known PRSS1 mutations, only the R122H was detected in a single subject and the A16V in two subjects in the cohort, strengthening that HP-associated PRSS1 mutations are rare in ICP. Additional missense mutations, including P36R, E79K, G83E, K92N and V123M, were identified once separately. By analogy with the known PRSS1 mutations, predisposition to pancreatitis by some of them, particularly the V123M autolysis cleavage site mutation, is suspected. Functional analysis is expected to clarify their possible medical consequences.

Nramp2 analysis in hemochromatosis probands

The mechanism that leads to iron overload in hereditary hemochromatosis is not yet fully understood and genes other than HFE may be involved. Nramp2 is an intestinal iron transporter, upregulated by dietary iron deficiency, which also colocalizes with transferrin in recycling endosomes. The purpose of the present study was to analyze the coding region of the Nramp2 gene in 14 hemochromatosis probands which did not carry any HFE mutations on both chromosomes. We confirmed the existence of a polymorphism (1254 T --> C), which presumably is not associated with hereditary hemochromatosis, but we did not find any mutation. On the other hand, we identified 17 splice variants of the Nramp2 mRNA. Eight corresponded to activation of cryptic splicing sequences between exons 3 and 4. They were observed in a majority of hemochromatosis probands and control subjects. This indicates the existence of an important splicing instability in this region. At this stage, the biological significance of these variants is unclear. Our study did not find evidence for the involvement of the Nramp2 gene in hereditary hemochromatosis. The remaining question is whether hemochromatosis probands in our study have iron overload because of environmental factors or due to mutation in gene(s) other than HFE and Nramp2.

Mutation analysis in the HFE gene in patients with hereditary haemochromatosis in Saguenay-Lac-Saint-Jean (Quebec, Canada)

A mutation analysis of the HFE gene followed, when applicable, by sequencing was performed on 47 patients with hereditary haemochromatosis (HH) living in Saguenay-Lac-Saint-Jean. The C282Y and H63D mutations were present on 50% and 20.3% of the HH chromosomes respectively. These frequencies were very different from those found in other populations and could be, at least partially, the result of a founder effect. No new mutation was identified among the remaining 28.1% of the HH chromosomes. Five of the eight probands with no mutation in the HFE gene had a severe and early onset suggestive of juvenile haemochromatosis.

Clinical and molecular aspects of juvenile hemochromatosis in Saguenay-Lac-Saint-Jean (Quebec, canada)

We report the clinical, biochemical, and genetic characteristics of 13 hemochromatosis patients from Saguenay-Lac-Saint-Jean in whom the first symptoms appeared before age 30. Although the mean age at onset of the first symptoms was 21. 5 years, their mean age at diagnosis was 23.8 years; the diagnosis was particularly delayed among women. Seventy-seven percent of the patients had hypogonadotrophic hypogonadism and 69% heart failure and/or cardiac arrhythmias. Genetic analysis of the HFE gene revealed heterozygosity for the C282Y mutation in 2 patients and for the S65C mutation in 2 others and homozygosity for the H63D mutation in 1 patient. The remaining 8 patients had no identified mutation in the HFE gene, although sequencing of all seven codons and intron-exon junctions was performed (5 patients). All 13 patients fulfill the clinical criteria of juvenile hemochromatosis and represent the largest cluster thus far reported.

HFE mutations analysis in 711 hemochromatosis probands: evidence for S65C implication in mild form of hemochromatosis

Hereditary hemochromatosis (HH) is a common autosomal recessive genetic disorder of iron metabolism. The HFE candidate gene encoding an HLA class I-like protein involved in HH was identified in 1996. Two missense mutations have been described: C282Y, accounting for 80% to 90% of HH chromosomes, and H63D, which is associated with a milder form of the disease representing 40% to 70% of non-C282Y HH chromosomes. We report here on the analysis of C282Y, H63D, and the 193A-->T substitution leading to the S65C missense substitution in a large series of probands and controls. The results confirm that the C282Y substitution was the main mutation involved in hemochromatosis, accounting for 85% of carrier chromosomes, whereas the H63D substitution represented 39% of the HH chromosomes that did not carry the C282Y mutation. In addition, our screening showed that the S65C substitution was significantly enriched in probands with at least one chromosome without an assigned mutation. This substitution accounted for 7.8% of HH chromosomes that were neither C282Y nor H63D. This enrichment of S65C among HH chromosomes suggests that the S65C substitution is associated with the mild form of hemochromatosis.

[The hemochromatosis gene (HFE). Molecular analysis--diagnostic applications]

Hemochromatosis is the most common single gene disorder in Caucasian populations. Regulation of iron balance by intestine is impaired, leading to a widespread deposition of iron, and the disease is associated with an increased risk of hepatocellular carcinoma. Typically the excess of iron treated by phlebotomies is performed in our Blood Center. In 1996 an original paper identifying HFE as a strong candidate gene for hemochromatosis was published and two mutations were described (C282Y and H63D). The former results in a cysteine to tyrosine substitution at amino acid 282 and was found in different patient populations up to 80-90% of patients homozygous for the C282Y mutation. The frequency of the second variant H63D is also increased in hemochromatosis patients but its penetrance is probably not complete. Assessing clinical implications is a new way of identifying patients at risk for this frequent and probably underdiagnosed disease, and important because treatment by venesections is safe with a proven benefit in preventing development of the disease. Four hundred and eighty patients were included in our study and we have shown in this work a correlation between the genotype and the phenotypic presentation of the disorder, with patients homozygous for the C282Y mutation having a greater excess of iron.

Phenotype-genotype correlation in haemochromatosis subjects

Haemochromatosis is a common autosomal recessive genetic disorder of iron metabolism. A candidate gene was recently identified (HLA-H) and two amino acid substitutions (C282Y and H63D) were characterized. Haemochromatosis probands (n = 478) from Brittany were selected from their iron status markers, primarily serum iron, serum ferritin and transferrin saturation. We investigated the relationships between haemochromatosis phenotype and genotypes at the HLA-H locus and surrounding markers. As already reported, we observed that the C282Y substitution is unambiguously associated with the haemochromatosis phenotype, haemochromatosis patients homozygous for the substitution (Tyr/Tyr) accounting for 81.2% of all haemochromatosis patients. A clear heterogeneity in serum ferritin and transferrin saturation values, and in iron removed by phlebotomy was observed among haemochromatosis patients that is correlated with the presence of two subgroups of individuals homozygous and non-homozygous for the mutant allele C282Y, the latter being characterized by lower phenotypic values. In this subgroup, sequencing did not reveal any other mutation in the HLA-H gene, hence the genotype remained unclear. Thus, an additional non-genetic cause, other mutations or another gene can not be excluded as explanations for the results in these patients.

Identical intragenic microsatellite haplotype found in cystic fibrosis chromosomes bearing mutation G551D in Irish, English, Scottish, Breton and Czech patients

Mutation G551D of exon 11 of the cystic fibrosis transmembrane conductance regulator gene is one of the most common mutations in patients of European origin. In order to test the hypothesis that the mutation is identical by descent in these patients, we have studied haplotypes for the three intragenic microsatellite markers IVS8CA, IVS17bTA and IVS17bCA from 92 patients bearing this mutation, who had been referred to laboratories in Ireland, Scotland, England, France (Brittany) and the Czech Republic. In all cases we found that only haplotype 16-7-17 is associated with mutation G551D. Our results support the hypothesis of identity by descent of all cystic fibrosis chromosomes bearing mutation G551D in these patient populations, and suggest that given the combined mutation rate of the microsatellite markers, there is a low probability (p < 0.05) that the haplotype where mutation G551D first occurred remained unaltered for more than 170 generations.

HLA-DRB and -DBQ typing by PCR amplification using sequence-specific primers (PCR-SSP): assessment after 1 year of routine use by three laboratories

Using sequence-specific amplifications, a practical and fast technique for DRB and DQB typing has been developed. The primers are chosen in order to amplify groups of alleles corresponding to the same serological specificity. In a second step, precise allelic determination is obtained by studying the restriction fragment length polymorphism of the PCR products. The experience of three laboratories using this technique in the context of organ or bone marrow transplantation is reported.

Prenatal diagnosis of cystic fibrosis in different European populations: application of denaturing gradient gel electrophoresis

The cystic fibrosis transmembrane regulator gene, one of the most commonly mutated in the European population, was cloned in 1989 and since then has been extensively analysed in patients of various ethnic backgrounds. We have screened the entire coding sequences of the cystic fibrosis transmembrane regulator gene and identified many mutations and polymorphisms. In this paper we propose a general strategy to improve prenatal diagnosis and genetic counselling of cystic fibrosis (CF). As this approach based on denaturing gradient gel electrophoresis is adaptable to different populations, it greatly increases the sensibility and specificity of CF prenatal diagnosis.