Inflammatory bowel disease gene hunting by linkage analysis: rationale, methodology, and present status of the field

A Case of Classical Polyarteritis Nodosa Complicated by Ulcerative Colitis

Classical polyarteritis nodosa (PAN) is a term that includes patients with necrotizing inflammation of medium-sized arteries and excludes those with microscopic vessel involvement. Although gastrointestinal manifestations are not unusual in patients with classical PAN, the association with ulcerative colitis has been reported only rarely. We describe a patient with classical PAN complicated by bilateral renal artery aneurysms with subsequent rapture and perirenal hemorrhages. He was successfully treated, and the bilateral renal aneurysms resolved with steroid therapy. Two years later, the patient presented with hematochezia. Colonoscopy revealed inflamed rectal mucosa with bleeding ulcers. Histologic findings of biopsy specimens showed severe mucosal inflammation and crypt abscess. The patient was diagnosed with ulcerative colitis, and the symptoms attenuated after meselazine therapy.

Identification of genetic loci for basal cell nevus syndrome and inflammatory bowel disease in a single large pedigree

Basal Cell Nevus Syndrome (BCNS) is an autosomal dominant disease. PTCH1 gene mutations have been found responsible in many but not all pedigrees. Inflammatory Bowel Disease (IBD) is a complex genetic disorder, disproportionate in Ashkenazim, and characterized by chronic intestinal inflammation. We revisited a large Ashkenazim pedigree, first reported in 1968, with multiple diagnoses of BCNS and IBD, and with a common genetic cause for both disorders proposed. We expanded the pedigree to four generations and performed a genome-wide linkage study for BCNS and IBD traits. Twelve members with BCNS, seven with IBD, five with both diagnoses and eight unaffected were genotyped. Both non-parametric (GENEHUNTER 2.1) and parametric (FASTLINK) linkage analyses were performed and a validation through simulation was performed. BCNS linked to chromosome 9q22 (D9S1120) just proximal to the PTCH1 gene (NPL=3.26, P=0.003; parametric two-point LOD=2.4, parametric multipoint LOD=3.7). Novel IBD linkage evidence was observed at chromosome 1p13 (D1S420, NPL 3.92, P=0.0047; parametric two-point LOD=1.9). Linkage evidence was also observed to previously reported IBD loci on 4q, (D4S2623, NPL 3.02, P=0.012; parametric two-point LOD=2.15), 10q23 (D10S1225 near DLG5, NPL 3.33, P=0.0085; parametric two-point LOD=1.3), 12 overlapping the IBD2 locus (D12S313, NPL 2.6, P=0.018; parametric two-point LOD=1.52), and 7q (D7S510 and D7S3046, NPL 4.06, P=0.0035; parametric two-point LOD=2.18). In this pedigree affected by both BCNS and IBD, the two traits and their respective candidate genetic loci segregate independently; BCNS maps to the PTCH1 gene and IBD maps to several candidate regions, mostly overlapping previously observed IBD loci.

MICB microsatellite polymorphism is associated with ulcerative colitis in Chinese population

The MHC class I-related molecules A and B (MICA and MICB) are stress-inducible cell surface antigens that are recognized by immunocytes bearing the receptor NKG2D, including intestinal epithelial Vdelta1 gammadelta T cells, which may play a role in immunological reaction in intestinal mucosa. The present study was aimed to investigate the association of the microsatellite polymorphisms in the intron 1 of MICB and the MICA-MICB haplotype with the susceptibility to ulcerative colitis (UC) in Chinese population. The microsatellite polymorphisms of MICB were genotyped in unrelated 127 Chinese patients with UC and 193 ethnically matched healthy controls by a semiautomatic fluorescently labeled PCR method. All the subjects were the Chinese with Han nationality. The frequency of MICB-CA18 was significantly higher in UC patients compared with the healthy controls (14.0% vs. 5.8%, P = 0.0016, Pc = 0.024, OR = 2.637, 95%CI: 1.443-4.820) and was increased in the female patients compared with the female healthy controls (18.3% vs. 4.1%, P = 0.0006, Pc = 0.0080, OR = 5.224, 95%CI: 1.940-14.069). Thus, MICB-CA18 is positively associated with UC and female UC patients in Chinese population.

Polymorphism of HLA-DRB1 gene shows no strong association with ulcerative colitis in Chinese patients

The genetic factors predisposing to ulcerative colitis (UC) have remained totally unclear to date. This study aimed to investigate the role of HLA-DRB1 genetic polymorphism in the susceptibility to develop UC in Chinese patients. HLA-DRB1 genotyping was carried out in 72 unrelated patients with UC and 314 healthy controls by using polymerase chain reaction-sequence-specific primers (PCR-SSP). All of the patients and healthy controls are Han people in China. The frequency of DRB1*07 allele was increased in UC patients compared with healthy controls (19.4% vs. 9.2%, P = 0.0229, OR = 2.372, 95%CI: 1.181-4.766), but the significance disappeared when given Bonferroni correction (P(C) = 0.2977). Furthermore, compared with healthy controls, although HLA-DRB1*07, DRB1*16/DRB1*09 and DRB1*07/DRB1*12 genotypes were increased in frequency in the patients with extensive colitis, and the patients without extraintestinal manifestations (EIMs) carried an increased frequency of HLA-DRB1*07 and DRB1*07/DRB1*12 genotypes, these differences did not reach statistical significance after Bonferroni correction. HLA-DRB1 alleles showed no strong association with UC, and no HLA-DRB1 alleles or genotypes were strongly associated with clinical subgroups of UC in Chinese patients.

Environment as a Critical Factor for the Pathogenesis and Outcome of Gastrointestinal Disease: Experimental and Human Inflammatory Bowel Disease and Helicobacter-Induced Gastritis

Environmental factors play an important role in the manifestation, course, and prognosis of diseases of the gastrointestinal tract such as inflammatory bowel disease (IBD) and Helicobacter pylori-induced gastritis. These two disease complexes were chosen for a discussion of the contribution of environmental factors to the disease outcome in humans and animal models. Dissecting complex diseases like IBD and Helicobacter-induced gastritis has shown that the outcome of disease depends on the allelic constellation of a host and the microbial and physical environments. Host alleles predisposing to a disease in one genomic and/or environmental milieu may not be deleterious in other constellations; on the other hand, microbes can have different effects in different hosts and under different environmental conditions. The impact of the complex interaction between host genetics and environmental factors, particularly microflora, also underlines the importance of a defined genetic background and defined environments in animal studies and is indicative of the difficulties in analyzing complex diseases in humans.

Recent advances in the etiology and treatment of inflammatory bowel disease

Crohn's disease and ulcerative colitis, together comprising the inflammatory bowel diseases, currently affect up to 2 million people in the western developed countries. The pathogenesis of the disease is a complex one in which genetic, immunogenic, microbial and environmental factors contribute to the etiology of the disease. Recent advances in understanding the molecular mechanisms that determine this complex entity have provided insight for promising new therapies.

Defective acute inflammation in Crohn's disease: a clinical investigation

BACKGROUND

The cause of Crohn's disease has not been mechanistically proven. We tested the hypothesis that the disease is a form of immunodeficiency caused by impaired innate immunity.

METHODS

We investigated inflammatory responses in patients and controls by quantifying neutrophil recruitment and cytokine production after acute trauma, interleukin 8 secretion by cultured monocyte-derived macrophages after exposure to inflammatory mediators, and local inflammatory and vascular changes in response to subcutaneous injection of heat-killed Escherichia coli.

FINDINGS

In patients with Crohn's disease, trauma to rectum, ileum, or skin led to abnormally low neutrophil accumulation (differences from healthy individuals of 79%, n=8, p=0.0003; 57%, n=3, p=0.05; 50%, n=13, p<0.0001, respectively) and lower production of proinflammatory interleukin 8 (63%, n=7, p=0.003; 63%, n=3, p=0.05; 45%, n=8, p<0.0001) and interleukin 1beta (50%, n=8, p=0.0005). Interleukin 8 secretion by cultured macrophages was reduced after exposure to acute wound fluid (38%, n=50, p<0.0001), C5a (48%, n=41, p=0.0005), or tumour necrosis factor alpha (52%, n=27, p<0.0001). Local inflammatory reaction to inoculation with E coli was attenuated, as quantified by changes in bloodflow (ileal disease 50%, n=6, p=0.01; colonic disease 77%, n=6, p=0.0003). This response was mediated by nitric oxide in controls, was increased by sildenafil in patients, and was not related to CARD15 genotype.

INTERPRETATION

In Crohn's disease, a constitutionally weak immune response predisposes to accumulation of intestinal contents that breach the mucosal barrier of the bowel wall, resulting in granuloma formation and chronic inflammation. Polymorphisms in CARD15 do not underlie this phenotype, but incapacitate the NOD2 pathway that can compensate for impairment of innate inflammation. Current treatment of secondary chronic inflammation might exaggerate the underlying lesion and promote chronic disease.

MHC class I chain-related gene A-A5.1 allele is associated with ulcerative colitis in Chinese population

The human MHC class I chain-related gene A (MICA) plays a role in regulating protective responses by intestinal epithelial Vdelta1 gamma delta T cells and the polymorphism of MICA were reported to be related to several autoimmune diseases. The present study aimed to investigate the association of the microsatellite polymorphisms of TM region of MICA gene with the susceptibility to ulcerative colitis (UC) in Chinese population. The microsatellite polymorphisms of the MICA were genotyped in unrelated 86 Chinese patients with UC and 172 ethnically matched healthy controls by a semiautomatic fluorenscently labelled PCR method. All the subjects were the Chinese with Han nationality. The frequency of MICA-A5.1 homozygous genotype and A5.1 allele were significantly increased in UC patients compared with healthy controls (22.1%versus 7%, P = 0.0009, Pc = 0.0126, OR = 3.781, 95%CI: 1.738-8.225 and 30.2%versus 17.4%, P = 0.0014, Pc = 0.007, OR = 2.051, 95%CI: 1.336-3.148, respectively). Adjusted the effects of gender and age at onset, MICA-A5.1 homozygous genotype and A5.1 allele were also increased in the UC patients. Moreover MICA-A5.1 allele was significantly increased in frequency in the female UC patients (38.2%versus 21.0%, P = 0.0095, Pc = 0.0475, OR = 2.326, 95%CI: 1.234-4.382). Logistic regression analysis also revealed that gender was independently associated with UC patients carried MICA-A5.1 allele (P = 0.046, OR (male) = 0.511, 95% CI: 0.264-0.987). Although the UC patients with extensive colitis (32.5%versus 17.4% in the healthy controls, P = 0.005, Pc = 0.025) and the UC patients with extraintestinal manifestations (36%versus 17.4% in the healthy controls, P = 0.0039, Pc = 0.0195) were more likely to carry the MICA-A5.1 allele, EIMs was associated with extent of disease (P < 0.0001, OR (with EIMs) = 3.511, 95% CI 1.747-7.056) and MICA-A5.1 allele was not associated with UC patients with extensive colitis or with EIMs in the logistic regression analysis. Therefore, the MICA-A5.1 homozygous genotype and A5.1 allele were closely associated with UC and the MICA-A5.1 allele was positively associated with the female UC patients in Chinese population.

Single nucleotide polymorphisms in TNFSF15 confer susceptibility to Crohn's disease

The inflammatory bowel diseases (IBDs), Crohn's disease (CD) and ulcerative colitis, are chronic inflammatory disorders of the digestive tract. The pathogenesis of IBD is complicated, and it is widely accepted that immunologic, environmental and genetic components contribute to its etiology. To identify genetic susceptibility factors in CD, we performed a genome-wide association study in Japanese patients and controls using nearly 80,000 gene-based single nucleotide polymorphism (SNP) markers and investigated the haplotype structure of the candidate locus in Japanese and European patients. We identified highly significant associations (P = 1.71 x 10(-14) with odds ratio of 2.17) of SNPs and haplotypes within the TNFSF15 (the gene encoding tumor necrosis factor superfamily, member 15) genes in Japanese CD patients. The association was confirmed in the study of two European IBD cohorts. Interestingly, a core TNFSF15 haplotype showing association with increased risk to the disease was common in the two ethnic groups. Our results suggest that the genetic variations in the TNFSF15 gene contribute to the susceptibility to IBD in the Japanese and European populations.

A recombined haplotype in the major histocompatibility region contains a cluster of genes conferring high susceptibility to ulcerative colitis in the Spanish population

BACKGROUND

The most consistently described associations in ulcerative colitis (UC) have been with human leukocyte antigen (HLA) class II alleles. Our aim was to look for associations among distinct genetic polymorphisms in the major histocompatibility complex (MHC) that might play a role in determining the susceptibility to UC and especially to the extensive form of the disease.

METHODS

A case-control study was performed with a total of 253 patients with UC and 315 healthy controls recruited from a single Spanish center. All the samples and 4 cell lines carrying DRB1*0103 or DRB1*1501 alleles were typed for the HLA-DRB1 class II gene and for a panel of HLA class III markers (D6S273, BAT_2, TNFa, b, c, d, e, IKBL+738, MICA).

RESULTS

The frequency of the alleles DRB1*0103, IKBL+738(C) (extending our previous results) and BAT_2-8 (newly typed) was increased in patients compared with controls (P=0.00001, odds ratio [OR]=5.90; P=0.002, OR=2.42; and P=0.0001, OR=3.04, respectively), and these associations were greatest in patients with extensive disease compared with patients with distal disease (P=0.02, OR=2.53; P=0.002, OR=3.06; and P=0.03, OR=2.08, respectively). The allelic combination DRB1*0103/D6S273-5/BAT_2-8/TNFa11b4c1d3e3/IKBL+738(C)/MICA5.1 that includes the telomeric class III markers of the 7.1 ancestral haplotype is highly increased in patients with UC (P=0.0001, OR=10.57), especially in those with the extensive form of the disease (P=0.02, OR=3.41 extensive versus distal).

CONCLUSIONS

The above-mentioned pattern, most likely formed by recombination of the telomeric fragment of the MHC 7.1 ancestral haplotype, seems to be the most important genetic determinant of susceptibility to the extensive form of UC in our population.

NOD2 and Crohn's disease: loss or gain of function?

The human nucleotide binding and oligomerization domain (NOD)-containing protein family consists of some 25 members related to the Apaf-1/Ced-4 family of apoptosis regulators and certain plant disease-resistance genes (Inohara et al., 2004). One member, NOD2 (CARD15), has gained recent prominence through its association with increased susceptibility to several clinically important human inflammatory diseases, especially Crohn's disease (CD). NOD2 is a cytoplasmic molecule involved in sensing microbial cell wall components and regulating inflammatory processes and apoptosis. This review focuses on recent insights into the functions of normal and variant NOD2 proteins and the pathogenetic mechanisms underlying NOD2-associated inflammatory diseases.

Involvement of epidermal growth factor receptor in chemically induced mouse bladder tumour progression

This study was designed to investigate the role of the epidermal growth factor receptor (EGFR) and its ligands in chemically induced mouse bladder cancer. Bladder tumours were induced in C57Bl/6 and B6D2F1 mice by treatment with the carcinogen, N:-butyl-N:-(4-hydroxybutyl) nitrosamine (BBN). The levels of mRNA for EGFR and its ligands were analysed by reverse transcription-polymerase chain reaction (RT-PCR) in bladder tumours and in normal bladder urothelia. EGFR mRNA was detected in all tumours, transforming growth factor alpha (TGFalpha) mRNA levels were similar to those in normal bladder urothelia or were decreased and mRNA levels for amphiregulin, heparin-binding epidermal growth factor-like factor (HB-EGF) and betacellulin were significantly higher than those in normal urothelia. Seven cell lines were derived from chemically induced tumours. These cell lines were able to grow in serum-free conditions. All the cell lines tested expressed the genes encoding EGFR and at least one of its ligands. Proliferation of these cell lines was inhibited by AG1478, a specific EGFR tyrosine kinase inhibitor, strongly suggesting that EGFR was involved in cell growth. As expected, EGFR was found to be phosphorylated in serum-free medium, this phosphorylation being inhibited by AG1478. Conditioned medium of a bladder cancer cell line had EGFR-stimulating activity and an antibody directed against EGFR inhibited proliferation by 45%. This suggests that tumour cell growth is stimulated by an autocrine loop involving EGFR and secreted growth factors. AG1478 decreased the expression of genes for amphiregulin, HB-EGF and betacellulin, showing that EGFR activation induces up-regulation of the EGFR ligands. These results suggest that EGFR plays a critical role in bladder tumour progression.