A patient with hereditary hemochromatosis, ulcerative colitis, and primary sclerosing cholangitis: genetic aspects

This report describes a family in which the rare combination of hereditary hemochromatosis, ulcerative colitis and primary sclerosing cholangitis was found. Subsequent to the index patient, who had all three diseases, a screening was done in his parents and siblings that included HLA-DR, HLA-DQ and HFE typing, ANCAs, liver tests and sigmoidoscopy with histology. On the basis of HLA and HFE typing, three probable haplotypes could be distinguished. The genetics of inflammatory bowel disease and hereditary hemochromatosis are discussed.

Analysis of a positional candidate gene for inflammatory bowel disease: NRAMP2

Genome scans have identified a region spanning 40 cM on the long arm of chromosome 12 as a susceptibility locus for inflammatory bowel disease (IBD). This locus contains several candidate genes for IBD, one of which is the gene for the natural resistance associated macrophage protein 2 (NRAMP2). This protein is a divalent cation transporter and is expressed in many cells and tissues. The putative role of this protein in innate immunity prompted us to investigate a possible relationship between NRAMP2 and IBD. We assessed the frequency of four restriction fragment length polymorphisms (IVS2+11A/G, IVS4+44C/A, 1254T/C, and IVS15Ex16-16C/G) in a group of 155 Crohn's disease (CD) patients, 114 ulcerative colitis (UC) patients, and 189 healthy controls. Linkage analysis was performed in a group of 70 families with multiple members suffering from IBD. We searched for additional intragenic markers and mutations by sequence analysis of the natural resistance-associated macrophage 2 gene of 33 CD patients, with a positive family history for IBD. We identified one novel restriction fragment length polymorphism in intron 15 of the gene. The frequency of the rare allele is: 0.08 in our control population. An increased frequency of this allele was found in CD patients but this difference did not reach statistical significance. A weak association between CD and homozygosity for the G allele of the IVS2+11A/G was found (OR [odds ratio] = 2.2, CI [confidence interval] = 1.3-3.9, chi2 = 8.4, p = 1.013). Nonparametric linkage analysis and transmissions disequilibrium tests did not provide evidence for linkage of NRAMP2 to IBD, UC, or CD. Sequence analysis of the exons and the iron-responsive element in a panel of 33 CD patients did not reveal any mutations in NRAMP2. Our association, linkage, and sequence analysis in IBD shows that the putative genetic risk factor on chromosome 12 likely is not NRAMP2. The weak association between the G/G genotype of IVS2+11A/G and CD may be due to linkage disequilibrium with a nearby disease-causing gene.

HLA-DR and -DQ phenotypes in inflammatory bowel disease: a meta-analysis

BACKGROUND

Susceptibility to inflammatory bowel disease (IBD) is partially genetically determined and the HLA class II genes are candidates for a role in genetic susceptibility to IBD, because their products play a central role in the immune response. Multiple studies have reported associations between HLA-DR or -DQ phenotypes and either ulcerative colitis or Crohn's disease, but much of the data are still controversial.

AIMS

To estimate overall associations between HLA class II phenotypes and IBD, and to establish the relative risk conferred by HLA-DR and -DQ phenotypes by meta-analysis.

METHODS

Medline was searched for publications reporting on the relation between IBD and HLA class II phenotypes. Raw data were extracted by recalculating the number of phenotypes or the number of alleles of the main antigens. Odds ratios and confidence intervals were calculated according to the Mantel-Haenszel method.

RESULTS

DR2, DR9, and DRB1*0103 were positively associated with ulcerative colitis, and a negative association was found for DR4 and ulcerative colitis. For Crohn's disease a positive association was found with DR7, DRB3*0301, and DQ4 and a negative association with DR2 and DR3.

CONCLUSIONS

Both ulcerative colitis and Crohn's disease are associated with specific HLA class II phenotypes. Further analysis of these phenotypes and subgroup analysis may elucidate how these alleles contribute to susceptibility to IBD.

Inflammatory bowel disease and the genes for the natural resistance-associated macrophage protein-1 and the interferon-gamma receptor 1

The genes for the interferon-gamma receptor 1 and the natural resistance-associated macrophage protein 1 (NRAMP1) control the immune response to intracellular microbial pathogens. Such pathogens, in particular Mycobacterium paratuberculosis, have been implicated in the pathogenesis of Crohn's disease. We studied markers in the genes for NRAMP1 and two mutations in the interferon-gamma receptor in relation to inflammatory bowel disease (IBD) in the following groups: 270 healthy individuals, 74 patients with Crohn's disease, 72 patients with ulcerative colitis, and 40 patients with primary sclerosing cholangitis. We studied the allele frequencies of two restriction fragment length polymorphisms in the gene for NRAMP1 and the prevalence of two mutations in the interferon-gamma receptor 1 gene. The markers in the NRAMP1 gene were not associated with inflammatory bowel disease. Also, the mutations in the interferon-gamma receptor 1 were not found in the 186 IBD patients. Genetic markers in NRAMP1 are thus not associated with IBD. Therefore this gene is not likely to play a role in the pathogenesis of IBD. The mutation in the interferon-gamma receptor was not found in our IBD patients group.

Five genetic markers in the interleukin 1 family in relation to inflammatory bowel disease

BACKGROUND

An imbalance between the proinflammatory cytokine interleukin 1 beta (IL-1 beta) and the anti-inflammatory cytokine IL-1 receptor antagonist (IL-1ra) has been postulated as a pathogenic factor in inflammatory bowel disease (IBD).

AIMS

To study allelic frequencies of novel polymorphisms in the genes for IL-1 beta and IL-1ra in patients with IBD and to assess the relation between ex vivo cytokine production and allelic variants of the IL-1 beta and IL-1ra genes.

SUBJECTS

Two hundred and seventy healthy controls, 74 patients with ulcerative colitis (UC), 72 with Crohn's disease (CD), 40 with primary sclerosing cholangitis for the allelic frequencies, and 60 healthy individuals for the ex vivo stimulation test.

METHODS

Genotyping was performed by polymerase chain reaction and subsequent cleavage with specific endonucleases (Mwo1, MspAI1, Alu1, Taq1, BsoF1) for five novel restriction fragment length polymorphisms (RFLPs) in the genes for IL-1ra and IL-1 beta.

RESULTS

No significant differences were found in the allelic frequencies or allele carriage rates of the markers in the IL-1 beta and IL-1ra genes between CD, UC, and healthy controls. No association between the genetic markers and cytokine production levels was observed. Patients with UC carried the combination of both the infrequent allele of the Taq1 RFLP and the Mwo1 RFLP significantly more frequently (35.2% in UC versus 71.1% in controls).

CONCLUSIONS

UC is associated with carriage of both infrequent alleles of the Taq1 and Mwo1 RFLPs. However, it could not be confirmed whether the association reflects a pathogenic mechanism underlying UC.

Developmental regulation of epidermal growth factor receptor kinase in rat intestine

BACKGROUND/AIMS

Intraluminal epidermal growth factor (EGF) may regulate intestinal growth and function. The ontogeny, localization, and phosphorylation of the EGF receptor in rat small intestine were studied.

METHODS

EGF-receptor phosphorylation was assayed by antiphosphotyrosine Western blot after EGF administration in vivo and EGF incubation to everted sacs in vitro. EGF-receptor abundance and localization were assayed by Western blot and immunofluorescence using anti-EGF-receptor antibodies.

RESULTS

In vivo, orogastric EGF enhanced EGF-receptor phosphorylation in newborn rat jejunum and liver. However, intraluminal EGF had no effect on EGF-receptor phosphorylation in adult intestine or liver. In vitro, mucosal EGF stimulated a fourfold increase in EGF-receptor phosphorylation in suckling jejunum but not in weanling or adult jejunum. In Western blot, EGF-receptor abundance was similar in 22-day-old fetal, 8-day-old suckling, and adult jejunum. In both crypt and villus, EGF-receptor was localized to the basolateral membrane but not to the apical membrane in fetal, suckling, and adult jejunum.

CONCLUSIONS

Mucosal EGF stimulates EGF-receptor phosphorylation in immature but not in mature intestine. These differences are not explained by EGF-receptor abundance or localization and suggest that the greater mucosal permeability of the immature gut may allow EGF to bind to the EGF-receptor in the basolateral membrane to mediate its effects in suckling rat intestine.

Orogastric EGF enhances c-neu and EGF receptor phosphorylation in suckling rat jejunum in vivo

Epidermal growth factor (EGF) in rat milk stimulates intestinal growth. We examined the role of EGF-stimulated tyrosine kinase activity in vivo in this process using an affinity-purified anti-phosphotyrosine antibody in Western blot. Jejunal sacs from fasted 8-day-old rat pups were incubated with intraluminal EGF and were then assayed for phosphotyrosyl proteins (p-Tyr) by Western blot. A 170-kDa p-Tyr was present in EGF-treated sacs but not in control. A 190-kDa p-Tyr was constitutively present in control but increased in abundance in EGF-treated sacs. Dose-response experiments demonstrated that the increase in p-Tyr was present at 100 ng/ml EGF, which is within the physiological range. The 170- and 190-kDa p-Tyr was confirmed by immunoprecipitation to be the EGF receptor and c-neu, respectively. A similar response was also observed in the jejunum after orogastric gavage feeding of EGF. By use of indirect immunofluorescence, the EGF receptor was localized primarily to the basolateral membrane of both the crypt and villus epithelium. c-neu was localized primarily in the villus enterocyte basolateral membrane. These data demonstrate that intraluminal EGF stimulates rapid tyrosine phosphorylation of the EGF receptor in vivo and that c-neu is a major substrate of the EGF receptor in suckling jejunum. The basolateral membrane localization of the EGF receptor and c-neu suggests that EGF is rapidly transported across the intestinal epithelium in suckling rat jejunum.