DLG5 R30Q variant is a female-specific protective factor in pediatric onset Crohn's disease

A double-edged sword: DLG5 in diseases

Discs large homolog 5 (DLG5), a key member of the membrane-associated guanylate kinase (MAGUKs) family, is a scaffold molecule for signal transduction complexes and is responsible for assembling receptors and adapters. This scaffold protein stabilizes adhesion and tight bonding complexes in many organs and tissues, and is involved of maintaining epithelial polarity. Although DLG5 plays a role in normal development in mice, it has also been linked to the onset and development of several diseases, particularly Crohn's disease and various malignancies. DLG5 has been shown to impact the progression of cancer through direct or indirect interactions with H-catenin, E-cadherin, Vimentin, p53, P21, Cyclin D1, TGF-β1, AKT, Hippo, and classic G protein signaling pathways. DLG5 and DLG5 variants has been found to have a dual role in human diseases. Although it is overexpressed in pancreatic adenocarcinoma, its expression is reduced in lung, liver, breast, prostate, and bladder cancers. However, two independent studies on glioblastoma (GBM) have shown the opposite effects of DLG5. Our study evaluates the existing literature on the role of DLG5 and DLG5 variants in disease processes, and summarizes the available data on the role of DLG5 in disease based on cell experiments, clinical samples, and animal models, while highlighting its future potential in disease treatment.

Impact of Female Gender in Inflammatory Bowel Diseases: A Narrative Review

Inflammatory bowel diseases show a gender bias, as reported for several other immune-mediated diseases. Female-specific differences influence disease presentation and activity, leading to a different progression between males and females. Women show a genetic predisposition to develop inflammatory bowel disease related to the X chromosome. Female hormone fluctuation influences gastrointestinal symptoms, pain perception, and the state of active disease at the time of conception could negatively affect the pregnancy. Women with inflammatory bowel disease report a worse quality of life, higher psychological distress, and reduced sexual activity than male patients. This narrative review aims to resume the current knowledge of female-related features in clinical manifestations, development, and therapy, as well as sexual and psychological implications related to inflammatory bowel disease. The final attempt is to provide gastroenterologists with a roadmap of female-specific differences, to improve patients' diagnosis, management, and treatment.

Gender-Based Differences in Response to Tumor Necrosis Factor Inhibitor Therapies for Ulcerative Colitis: Individual Participant Data Meta-Analyses of Clinical Trials

BACKGROUND

Gender-based differences are reported in inflammatory bowel diseases (IBD) pathogenesis, but their impacts on IBD outcomes are not well known. We determined gender-based differences in response to treatment with tumor necrosis factor inhibitor (TNFi) therapies in individuals with ulcerative colitis (UC).

METHODS

We used the Yale University Open Data Access (YODA) platform to abstract individual participant data from randomized clinical trials to study infliximab and golimumab as induction and maintenance therapies in moderately to severely active UC. Using multivariable logistic regression, we examined associations between gender and the endpoints of clinical remission, mucosal healing, and clinical response for each study individually and in a meta-analysis.

RESULTS

Of 1639 patients included in induction trials (Program of Ulcerative Colitis Research Studies Utilizing an Investigational Treatment-Subcutaneous [PURSUIT-SC], active ulcerative colitis trials [ACT] 1 and 2) and 1280 patients included in maintenance trials (Program of Ulcerative Colitis Research Studies Utilizing an Investigational Treatment-Maintenance [PURSUIT-IM], ACT 1 and 2), 696 (42.5%) and 534 (41.7%) were women, respectively. In a meta-analysis of induction trials, the adjusted odds ratios (aORs) of clinical remission (aOR, 0.55; 95% CI, 0.31-0.97), mucosal healing (aOR, 0.47; 95% CI, 0.27-0.83), and clinical response (aOR, 0.51; 95% CI, 0.29-0.90) in the treatment arm and of clinical remission in the placebo arm (aOR, 0.34; 95% CI, 0.15-0.82) were lower in men compared to women. There were no differences in outcomes by gender in the treatment and placebo arms in the meta-analysis of maintenance trials.

CONCLUSIONS

Men are less likely to achieve clinical remission, mucosal healing, and clinical response compared to women during induction treatment with TNFi for UC, but not during the maintenance phase. Future studies delineating the mechanisms underlying these observations would be informative.

Sex-based differences in inflammatory bowel diseases: a review

Sex-based differences in inflammatory bowel disease (IBD) pathogenesis, disease course, and response to therapy have been increasingly recognized, however, not fully understood. Experimental and translational models have been leveraged to investigate hypothesized mechanisms for these observed differences, including the potential modifying role of sex hormones and sex-dependent (epi)genetic and gut microbiome changes. The primary objective of this review is to comprehensively describe sex-based differences in IBD including epidemiology, pathogenesis, phenotypic differences, therapeutic response, and outcomes.

Overcoming difficulty in diagnosis and differential diagnosis of Crohn's disease: the potential role of serological and genetic tests

Crohn's disease (CD) represents a heterogeneous group of chronic inflammatory disorders with various phenotypes. Establishing a definite diagnosis of CD should be based upon a combined assessment of clinical, endoscopic, radiological and pathological features. Although segmental disease distribution, transmural inflammation and non-caseating epithelioid granulomas have been considered as a 'hallmarks' for CD, clear diagnosis of CD in some patients has been challenging, due to overlapping endoscopic, radiographic and histologic features with other inflammatory bowel disease-like conditions. Laboratory markers (serological and genetic tests) may provide additional clues for the diagnosis and differential diagnosis of CD. This review focuses on the application of the currently available serological and genomic markers and in diagnosis and differential diagnosis of CD.

Gender differences in paediatric patients of the swiss inflammatory bowel disease cohort study

PURPOSE

Gender differences in paediatric patients with inflammatory bowel disease (IBD) are frequently reported as a secondary outcome and the results are divergent. To assess gender differences by analysing data collected within the Swiss IBD cohort study database since 2008, related to children with IBD, using the Montreal classification for a systematic approach.

METHODS

Data on gender, age, anthropometrics, disease location at diagnosis, disease behaviour, and therapy of 196 patients, 105 with Crohn's disease (CD) and 91 with ulcerative or indeterminate colitis (UC/IC) were retrieved and analysed.

RESULTS

THE CRUDE GENDER RATIO (MALE : female) of patients with CD diagnosed at <10 years of age was 2.57, the adjusted ratio was 2.42, and in patients with UC/IC it was 0.68 and 0.64 respectively. The non-adjusted gender ratio of patients diagnosed at ≥10 years was 1.58 for CD and 0.88 for UC/IC. Boys with UC/IC diagnosed <10 years of age had a longer diagnostic delay, and in girls diagnosed with UC/IC >10 years a more important use of azathioprine was observed. No other gender difference was found after analysis of age, disease location and behaviour at diagnosis, duration of disease, familial occurrence of IBD, prevalence of extra-intestinal manifestations, complications, and requirement for surgery.

CONCLUSION

CD in children <10 years affects predominantly boys with a sex ratio of 2.57; the impact of sex-hormones on the development of CD in pre-pubertal male patients should be investigated.

Central role of the gut epithelial barrier in the pathogenesis of chronic intestinal inflammation: lessons learned from animal models and human genetics

The gut mucosa is constantly challenged by a bombardment of foreign antigens and environmental microorganisms. As such, the precise regulation of the intestinal barrier allows the maintenance of mucosal immune homeostasis and prevents the onset of uncontrolled inflammation. In support of this concept, emerging evidence points to defects in components of the epithelial barrier as etiologic factors in the pathogenesis of inflammatory bowel diseases (IBDs). In fact, the integrity of the intestinal barrier relies on different elements, including robust innate immune responses, epithelial paracellular permeability, epithelial cell integrity, as well as the production of mucus. The purpose of this review is to systematically evaluate how alterations in the aforementioned epithelial components can lead to the disruption of intestinal immune homeostasis, and subsequent inflammation. In this regard, the wealth of data from mouse models of intestinal inflammation and human genetics are pivotal in understanding pathogenic pathways, for example, that are initiated from the specific loss of function of a single protein leading to the onset of intestinal disease. On the other hand, several recently proposed therapeutic approaches to treat human IBD are targeted at enhancing different elements of gut barrier function, further supporting a primary role of the epithelium in the pathogenesis of chronic intestinal inflammation and emphasizing the importance of maintaining a healthy and effective intestinal barrier.

Dlg5 interacts with the TGF-β receptor and promotes its degradation

Discs large homolog 5 (Dlg5) is a member of the membrane-associated guanylate kinase adaptor family of proteins and is involved in epithelial-to-mesenchymal transition via transforming growth factor-β (TGF-β) signaling. However, the mechanism underlying the regulation of TGF-β signaling is unclear. We show here that Dlg5 interacts and colocalizes with both TGF-β type I (TβRI) and type II (TβRII) receptors at the plasma membrane. TβRI activation is not required for this interaction. Furthermore, the overexpression of Dlg5 enhances the degradation of TβRI. Proteasome inhibitors inhibited this enhanced degradation. These results suggest that Dlg5 interacts with TβRs and promotes their degradation.

Eosinophil associated genes in the inflammatory bowel disease 4 region: Correlation to inflammatory bowel disease revealed

AIM: To study the association between inflammatory bowel disease (IBD) and genetic variations in eosinophil protein X (EPX) and eosinophil cationic protein (ECP).

METHODS: DNA was extracted from ethylene diamine tetraacetic acid blood of 587 patients with Crohn’s disease (CD), 592 with ulcerative colitis (UC) and 300 healthy subjects. The EPX405 (G > C, rs2013109), ECP434 (G > C, rs2073342) and ECP562 (G > C, rs2233860) gene polymorphisms were analysed, by the 5’-nuclease allelic discrimination assay. For determination of intracellular content of EPX and ECP in granulocytes, 39 blood samples was collected and extracted with a buffer containing cetyltrimethylammonium bromide. The intracellular content of EPX was analysed using an enzyme-linked immunosorbent assay. The intracellular content of ECP was analysed with the UniCAP^® system as described by the manufacturer. Statistical tests for calculations of results were χ² test, Fisher’s exact test, ANOVA, Student-Newman-Keuls test, and Kaplan-Meier survival curve with Log-rank test for trend, the probability values of P < 0.05 were considered statistically significant.

RESULTS: The genotype frequency for males with UC and with an age of disease onset of ≥ 45 years (n = 57) was for ECP434 and ECP562, GG = 37%, GC = 60%, CC = 4% and GG = 51%, GC = 49%, CC = 0% respectively. This was significantly different from the healthy subject’s genotype frequencies of ECP434 (GG = 57%, GC = 38%, CC = 5%; P = 0.010) and ECP562 (GG = 68%, GC = 29%,CC = 3%; P = 0.009). The genotype frequencies for females, with an age of disease onset of ≥ 45 years with CD (n = 62), was for the ECP434 and ECP562 genotypes GG = 37%, GC = 52%, CC = 11% and GG = 48%, GC = 47% and CC = 5% respectively. This was also statistically different from healthy controls for both ECP434 (P = 0.010) and ECP562 (P = 0.013). The intracellular protein concentration of EPX and ECP was calculated in μg/10⁶ eosinophils and then correlated to the EPX 405 genotypes. The protein content of EPX was highest in the patients with the CC genotype of EPX405 (GG = 4.65, GC = 5.93, and CC = 6.57) and for ECP in the patients with the GG genotype of EPX405 (GG = 2.70, GC = 2.47 and CC = 1.90). ANOVA test demonstrated a difference in intracellular protein content for EPX (P = 0.009) and ECP (P = 0.022). The age of disease onset was linked to haplotypes of the EPX405, ECP434 and ECP562 genotypes. Kaplan Maier curve showed a difference between haplotype distributions for the females with CD (P = 0.003). The highest age of disease onset was seen in females with the EPX405CC, ECP434GC, ECP562CC haplotype (34 years) and the lowest in females with the EPX405GC, ECP434GC, ECP562GG haplotype (21 years). For males with UC there was also a difference between the highest and lowest age of the disease onset (EPX405CC, ECP434CC, ECP562CC, mean 24 years vs EPX405GC, ECP434GC, ECP562GG, mean 34 years, P = 0.0009). The relative risk for UC patients with ECP434 or ECP562-GC/CC genotypes to develop dysplasia/cancer was 2.5 (95%CI: 1.2-5.4, P = 0.01) and 2.5 (95%CI: 1.1-5.4, P = 0.02) respectively, compared to patients carrying the GG-genotypes.

CONCLUSION: Polymorphisms of EPX and ECP are associated to IBD in an age and gender dependent manner, suggesting an essential role of eosinophils in the pathophysiology of IBD.

Maternal imprinting and female predominance in familial Crohn's disease

BACKGROUND AND AIM

Although the genetic risk factors for familial and sporadic inflammatory bowel disease (IBD) seem identical, the relative risk for contracting IBD in the familial setting is larger as that seen in the population at large, suggesting an important role of epi- and/or paragenetic factors in familial IBD. Epidemiological data indicate a female predominance in IBD, but how this relates to familial IBD has not been assessed.

METHODS

Familial IBD patients (N=608) were compared with a cohort of 415 sporadic IBD patients with regards to the patterns of sex and disease type distribution. The imprinting pattern in 87 families in which both a parent and a child had IBD was tested using Galton binominal statistics.

RESULTS

The percentage of females in familial IBD population was significantly higher (61%; female/male ratio 1.5) compared with sporadic IBD (54%; female/male ratio 1.2; p=0.011). The analysis of offspring sex distribution pattern revealed significantly higher female to female transmission compared with female to male transmission rate (36 vs. 18, respectively; p=0.02). A significantly higher number of mother to child transmissions (55 vs. 32 of father to child transmissions) was observed (p=0.018). The female imprinting was specifically related to Crohn's disease (31 vs. 14 mother vs. father to child transmissions, respectively; p=0.016).

CONCLUSION

We propose that a female sex-specific epigenetic inheritance pattern for Crohn's disease is a major contributing factor in the family-specific risk in Crohn's disease. Sex-specific manifestation of familial Crohn's disease can partly explain the epidemiologically observed increased relative risk for females for contracting IBD.

Role of Dlg5/lp-dlg, a membrane-associated guanylate kinase family protein, in epithelial-mesenchymal transition in LLc-PK1 renal epithelial cells

Discs large homolog 5 (Dlg5) is a member of the membrane-associated guanylate kinase adaptor family of proteins, some of which are involved in the regulation of epithelial-to-mesenchymal transition (EMT). Dlg5 has been described as a susceptibility gene for Crohn's disease; however, the physiological function of Dlg5 is unknown. We show here that transforming growth factor-β (TGF-β)-induced EMT suppresses Dlg5 expression in LLc-PK1 cells. Depletion of Dlg5 expression by knockdown promoted the expression of the mesenchymal marker proteins, fibronectin and α-smooth muscle actin, and suppressed the expression of E-cadherin. In addition, activation of JNK and p38, which are stimulated by TGF-β, was enhanced by Dlg5 depletion. Furthermore, inhibition of the TGF-β receptor suppressed the effects of Dlg5 depletion. These observations suggest that Dlg5 is involved in the regulation of TGF-βreceptor-dependent signals and EMT.

Sex differences in disease risk from reported genome-wide association study findings

Men and women differ in susceptibility to many diseases and in responses to treatment. Recent advances in genome-wide association studies (GWAS) provide a wealth of data for associating genetic profiles with disease risk; however, in general, these data have not been systematically probed for sex differences in gene-disease associations. Incorporating sex into the analysis of GWAS results can elucidate new relationships between single nucleotide polymorphisms (SNPs) and human disease. In this study, we performed a sex-differentiated analysis on significant SNPs from GWAS data of the seven common diseases studied by the Wellcome Trust Case Control Consortium. We employed and compared three methods: logistic regression, Woolf's test of heterogeneity, and a novel statistical metric that we developed called permutation method to assess sex effects (PMASE). After correction for false discovery, PMASE finds SNPs that are significantly associated with disease in only one sex. These sexually dimorphic SNP-disease associations occur in Coronary Artery Disease and Crohn's Disease. GWAS analyses that fail to consider sex-specific effects may miss discovering sexual dimorphism in SNP-disease associations that give new insights into differences in disease mechanism between men and women.

Transmission distortion in Crohn's disease risk gene ATG16L1 leads to sex difference in disease association

BACKGROUND

Crohn's disease (CD), an inflammatory disease of the bowel, affects millions of people around the world. Evidence suggests that disease onset and pathogenesis differ between males and females. Yet no comprehensive efforts exist to assess the sex-specific genetic architecture of CD.

METHODS

We used genotyping data from a cohort of 1748 CD cases and 2938 controls to investigate 71 meta-analysis-confirmed CD risk loci for sex differences in disease risk. We further validated the significant results in separate cohorts of 968 CD cases and 2809 controls, and performed a meta-analysis across datasets.

RESULTS

The single nucleotide polymorphism (SNP) rs3792106 (C/T) in ATG16L1 showed a significant sex effect with P-value 6.9 × 10(-13) and allelic odds ratio 1.48 in females, and P-value 0.013 and odds ratio 1.22 in males (odds ratio heterogeneity P-value 0.037). Surprisingly, the difference was found to arise from a discrepancy in allele frequencies between male and female controls (P-value 0.0045) rather than cases. We found similar results for this SNP in the separate validation datasets. Using 155 HapMap 3 trios, we detected significant maternal overtransmission of the T allele at rs3792106 (P-value 0.027).

CONCLUSIONS

Our results indicate that different transmission patterns between sexes may sustain the disparate allele frequencies at rs3792106 in healthy populations, and furthermore that a virus-risk variant mechanism implicated in CD alters the distribution in diseased patients. To our knowledge, this is the first report of sex-specific CD association in ATG16L1. The possible implications in CD and basic human biology present interesting areas for future investigation.

Role of genetics in the diagnosis and prognosis of Crohn's disease

Considering epidemiological, genetic and immunological data, we can conclude that the inflammatory bowel diseases are heterogeneous disorders of multifactorial etiology in which hereditability and environment interact to produce the disease. It is probable that patients have a genetic predisposition for the development of the disease coupled with disturbances in immunoregulation. Several genes have been so far related to the diagnosis of Crohn's disease. Those genes are related to innate pattern recognition receptors, to epithelial barrier homeostasis and maintenance of epithelial barrier integrity, to autophagy and to lymphocyte differentiation. So far, the most strong and replicated associations with Crohn's disease have been done with NOD2, IL23R and ATG16L1 genes. Many genes have so far been implicated in prognosis of Crohn's disease and many attempts have been made to classify genetic profiles in Crohn's disease. CARD15 seems not only a susceptibility gene, but also a disease-modifier gene for Crohn's disease. Enriching our understanding on Crohn's disease genetics is important but when combining genetic data with functional data the outcome could be of major importance to clinicians.

Role of genetics in the diagnosis and prognosis of Crohn's disease

Considering the epidemiological, genetic and immunological data, we can conclude that the inflammatory bowel diseases are heterogeneous disorders of multifactorial etiology in which hereditability and environment interact to produce the disease. It is probable that patients have a genetic predisposition for the development of the disease coupled with disturbances in immunoregulation. Several genes have so far been related to the diagnosis of Crohn's disease. These genes are related to innate pattern recognition receptors, to epithelial barrier homeostasis and maintenance of epithelial barrier integrity, to autophagy and to lymphocyte differentiation. So far, the strongest and most replicated associations with Crohn's disease have been demonstrated with NOD2, IL23R and ATG16L1 genes. Many genes have so far been implicated in the prognosis of Crohn's disease and many attempts have been made for classification of genetic profiles in Crohn's disease. CARD15 seems to be not only a susceptibility gene, but also a disease-modifier gene for Crohn's disease. Enriching our understanding of Crohn's disease genetics is of value, but when combining genetic data with functional data the outcome could be of major importance to clinicians.

The functional -374T/A polymorphism of the receptor for advanced glycation end products may modulate Crohn's disease

The receptor for advanced glycation end products (RAGE) is involved in innate immune mechanisms. Polymorphisms of the RAGE gene have been described as a factor amplifying inflammation in susceptible patients, but the association with Crohn's disease (CD) is not known. The coding RAGE polymorphism G82S (rs2070600) and two promoter polymorphisms, -374T/A (rs1800624) and -429T/C (rs1800625), were studied in two samples from Germany and the United States consisting of 421 and 317 CD patients and 549 and 218 controls, respectively. To test the functional relevance, additional data on serum soluble RAGE (sRAGE), tissue RNA, and protein levels were collected and immunohistochemical stainings of bowel tissue of CD patients and healthy controls as well as models of experimental (dextran sodium sulfate-induced) colitis in RAGE knockout and wild-type mice were performed. The -374T/A RAGE promotor single nucleotide polymorphism (SNP) was negatively associated with CD (odds ratio = 0.708, 95% confidence interval = 0.535-0.938, P = 0.016) and with stenosis (OR = 0.627, P = 0.04) in the German sample. Transmission disequilibrium testing confirmed an undertransmission of the -374A allele. Serum sRAGE levels were higher in patients in complete remission of the -374AA/TA group (1,975 ± 299 pg/ml; -374TT group: 1,310 ± 153 pg/ml SE, P < 0.05) and showed a trend toward decreased levels in CD patients with active disease compared with CD patients in remission. Further in vitro and in vivo studies indicated that an increase of sRAGE ameliorates inflammation. The -429T/C and the G82S polymorphism were not associated with CD. The -374T/A RAGE polymorphism leading to facilitated RAGE gene transcription may to some degree protect from developing a stricturing subphenotype of CD, most likely by increasing levels of sRAGE, which neutralizes proinflammatory mediators.

Early-onset Crohn disease is associated with male sex and a polymorphism in the IL-6 promoter

AIMS

Pediatric onset of Crohn disease (CD) is characterized by male sex predominance while adult-onset disease demonstrates female sex predominance. It has been postulated that this phenomenon may be genetically determined or due to an effect of estrogen on age of onset. Interleukin (IL)-6 modulates the TH17 pathway, and the IL-6 promoter is modulated by estrogen, possibly linking genetically determined inflammation and the presence of estrogen. The aim of our study was to investigate whether differences in IL-6 promoter genotype could explain male sex in earlier disease onset.

PATIENTS AND METHODS

We genotyped 333 patients with CD and 100 controls, 162 pediatric-onset patients (age of onset 18 years and younger) for the IL-6-174 polymorphic site. Genotype, sex, and age of onset were compared.

RESULTS

Males with IL-6-174GG genotype (the wild-type allele) had an increased risk for a younger age of onset compared to males with IL-6-174GC or CC genotype (G --> C genotype), hazard ratio (HR) 1.49, P = 0.02, 95% confidence interval (CI) 1.07-2.09. Females with GG genotype were not found to have an increased risk for a younger age of onset compared with females with G --> C genotype, HR 1.01, P = 0.96, 95% CI 0.72-1.41.

CONCLUSIONS

Males with IL-6-174GG genotype are prone to develop CD at a younger age than males with the IL-6-174G --> C genotype. Our study suggests that age of onset may be modified by the IL-6-174GG genotype and this modification is sex dependent. This may be due to increased transcription of IL-6, an effect that may be repressed by estrogen in females.

The genetics of Crohn's disease

From epidemiological data, based on concordance data in family studies, via linkage analysis to genome-wide association studies, we and others have accumulated robust evidence implicating more than 30 distinct genomic loci involved in the genetic susceptibility to Crohn's disease (CD). These loci encode genes involved in a number of homeostatic mechanisms: innate pattern recognition receptors (NOD2/CARD15, TLR4, CARD9), the differentiation of Th17-lymphocytes (IL-23R, JAK2, STAT3, CCR6, ICOSLG), autophagy (ATG16L1, IRGM, LRRK2), maintenance of epithelial barrier integrity (IBD5, DLG5, PTGER4, ITLN1, DMBT1, XBP1), and the orchestration of the secondary immune response (HLA-region, TNFSF15/TL1A, IRF5, PTPN2, PTPN22, NKX2-3, IL-12B, IL-18RAP, MST1). While many of these loci also predispose to pediatric CD, an additional number of childhood-onset loci have been identified recently (e.g., TNFRSF6B). Not only has the identification of these loci improved our understanding of the pathophysiology of CD, this knowledge also holds real promise for clinical practice.

Research progress in susceptible genes of inflammatory bowel disease

The mechanism of inflammatory bowel disease (IBD) is partially understood, but it is certain that a genetic predisposition, through the inheritance of a number of contributory genetic polymorphisms, contributes to the pathogenesis of IBD. These variant forms of genes may be associated with an abnormal response to normal luminal bacteria. Those genes that have been consistently associated with IBD thus far primarily fall into one of three classes: those affecting bacterial recognition, those affecting immune response, and a third group affecting mucosal transport polarity or mucosal transporter function. This article reviews the IBD related genes mentioned above.

Interleukin-10 promoter polymorphisms influence susceptibility to ulcerative colitis in a gender-specific manner

OBJECTIVE

Pathological evidence supports a potential role of the pro- and anti-inflammatory cytokine network in the pathogenesis of inflammatory bowel disease (IBD). Moreover, associated studies suggest a possible involvement of cytokine-related genes in IBD susceptibility. In this study, we evaluated the effect of the anti-inflammatory interleukin-10 (IL10) gene on ulcerative colitis (UC).

MATERIAL AND METHODS

Two functional single nucleotide polymorphisms (-1082 G/A, -819 T/C) in the IL10 promoter in 203 Italian sporadic UC patients and 391 controls were determined using high-resolution melting analysis.

RESULTS

The frequency of the -1082A allele was significantly higher in the UC patients than in controls (p=0.00003); -1082 genotype frequencies were also significantly different between UC patients and controls (p=0.0001). Allele and genotype frequencies of -819 T/C were not significantly associated with UC. Furthermore, the frequencies of haplotypes -1082A/-819C and -1082A/-819T, which have been reported to have a lower promoter activity, were significantly higher in UC patients than in controls (p=0.0004). After gender stratification, we found a significant difference in the -1082A allele (p=0.00004) and genotype (p=0.0002) frequencies only between female UC patients and controls; the same result was obtained for the -1082A/-819C and -1082A/-819T haplotypes (p=0.0006).

CONCLUSIONS

A gender effect is observed, with women of AG/AA IL10 genotypes and AC/AT haplotypes having a higher risk of developing UC at a younger age. This finding could be related to the previously documented lower IL10 production associated with the -1082A allele and to the IL10 down-regulating effect of estrogens.

New global map of Crohn's disease: Genetic, environmental, and socioeconomic correlations

Seventy-five years after the initial characterization of Crohn's disease (CD), much remains obscure about its etiology. The authors sought to evaluate the incidence trends of the last 25 years worldwide, and the existence of potential correlations with genetic, environmental, and socioeconomic factors that could be etiologically implicated in the pathogenesis of CD. Relevant medical literature for individual countries on the incidence of CD, on the incidence of associated genetic mutations, and on the incidence of suggested etiologic infectious agents such as Mycobacterium avium paratuberculosis were retrieved from published medical literature, reports from relevant international congresses, and through official reports from national health authorities. Increasing trends have been observed almost worldwide, with a broad north-south gradient still prevailing in Europe. Distinct regions of New Zealand, Canada, Scotland, France, the Netherlands, and Scandinavia represent the highest incidence areas. Industrialized status and affluence are the common denominators between endemic areas, but are too broad as terms to strongly indicate any particular etiological role. The increasing trends observed in Asia still account for a low prevalence of the disease and may represent increased detection and diagnostic ability of local health systems. Genetic associations are variably reproduced worldwide, in a manner inconsistent with a strong etiologic relationship. Data on paratuberculosis incidence are scarce, and the existing ones are ambivalent regarding an even indirect correlation between CD and an infectious trigger.

The Crohn's disease susceptibility gene DLG5 as a member of the CARD interaction network

Discs large homolog 5 (DLG5), a member of the membrane-associated guanylate kinase (MAGUK) family of scaffolding proteins, has been associated with Crohn's disease (CD), but its role in the pathogenesis of this inflammatory bowel disease is disputed. Here, we used sequence comparisons and phylogenies to analyse the DLG5 gene and its protein product. We identified a 5' exon, which codes for an N-terminal caspase recruitment domain (CARD) and experimentally confirmed its expression in colonic tissue. DLG5 shares this new domain with nucleotide-binding oligomerisation domain containing 2 (NOD2); the first CD susceptibility factor identified in genetic studies. An extensive phylogenetic analysis redefines the family organisation of the MAGUK proteins: DLG5 is closely related to CARD10, CARD11 and CARD14, CARD-containing proteins which initiate pro-inflammatory NFkappaB signalling, but not to DLG1-4, previously considered the closest related proteins. Therefore, we suggest renaming DLG5 to correctly annotate the gene in its phylogenetic and functional context. Our study provides evidence that the scaffolding protein DLG5 belongs to the CARD protein family. Thus, DLG5 likely acts in the regulation of NFkB activation or caspase activation as part of host defence mechanisms. As there is substantial crosstalk between CARD-mediated pathways, both CD susceptibility genes, NOD2 and DLG5, may interact functionally to contribute to CD risk.

Epidemiology, genes and inflammatory bowel diseases in childhood

There is evidence that inflammatory bowel disease is immunologically mediated and that genetic factors play an important aetiological role. The identification of disease susceptibility genes has led to significant progress in our understanding of the pathogenesis of Crohn's disease. Genes linked to Crohn's disease play critical roles in the normal function of the innate immune system, and genes linked to epithelial integrity may play a role in the pathogenesis of inflammatory bowel disease as well. However, the dynamic epidemiology of both Crohn's disease and ulcerative colitis suggests that extrinsic environmental factors acting at the population level may be involved in their pathogenesis. These environmental factors may be responsible for the rising incidence of inflammatory bowel disease.

The genetics of inflammatory bowel disease

Great progress in the understanding of the molecular genetics of inflammatory bowel disease (IBD) has been made over the last 10 years. Strong epidemiological evidence, based initially on concordance data in twin/family studies, led to the application of genome-wide linkage analysis involving multiply affected families and the identification of a number of susceptibility loci. Further characterization of the IBD1 locus on chromosome 16 led to the discovery of the NOD2/CARD15 gene as the first susceptibility gene in Crohn's disease for 2001. This landmark finding has led to a redirection of basic research in IBD with interest focused principally on regulation of the innate immune response and mucosal barrier function. Within the last year, the use of genome-wide association studies has provided new insights into primary pathogenetic mechanisms; several new genes such as the Interleukin-23 receptor (IL23R) and ATG16L1 (autophagy-related 16-like 1) genes are strongly implicated. Overall, these studies promise to change our fundamental understanding of IBD pathophysiology and to have implications for clinical practice.

Pediatric inflammatory bowel disease: clinical and molecular genetics

Pediatric-onset inflammatory bowel disease (IBD) is characterized by distinct phenotypic differences compared to adult-onset IBD. This raises the question whether early (pediatric) onset IBD represents the same disease process occurring in adults but merely at an earlier age or does IBD in children have a very different etiology and pathogenesis but with the same clinical presentation as adults. The use of techniques such as whole genome association studies to perform broad, unbiased screening for the contributions of common genetic variations to complex disease has rapidly assisted in the identification of several novel susceptibility loci associated with pediatric-onset Crohn's disease such as IL23R and ATG16L1. These genes join the already confirmed IBD susceptibility genes such as NOD2/CARD15, IBD5, and DLG5. Therefore, there is hope that advances in the field of clinical and molecular genetics will assist in answering the fundamental question of whether pediatric IBD has a different etiology and pathogenesis compared to adult IBD. This review examines the current status of clinical and molecular genetics of pediatric IBD, and highlights the differences between pediatric and adult IBD in disease phenotypes and genotypes. Finally, the future directions of genetic investigations in pediatric IBD are discussed.

TNFSF15 is an ethnic-specific IBD gene

BACKGROUND

Inflammatory bowel disease (IBD) is a clinically and, likely, genetically heterogeneous group of disorders. A recent report suggests that genetic variations in the TNFSF15 gene contribute to the susceptibility of IBD in both Japanese and Caucasian populations. The aim was to confirm the association between TNFSF15 high- and low-risk haplotypes and IBD in a Caucasian population.

METHODS

Five single-nucleotide polymorphisms (SNPs) that comprise the 2 common haplotypes were genotyped in 599 Caucasian patients with Crohn's disease (CD), 382 Caucasian patients with ulcerative colitis (UC), and 230 ethnically matched healthy controls, including both Jews and non-Jews.

RESULTS

The previously reported 'risk' haplotype was not associated with CD or UC (88.2% in CD cases versus 88.3% in controls, P = 0.96; 88.1% in UC cases versus 88.3% in controls, P = 0.78). We did, however, observe an increased frequency of the "protective" haplotype in non-Jewish controls for both CD and UC (38.8% CD cases versus 50% controls, P = 0.01; 37.3% UC cases versus 50% controls, P = 0.01) with no such effect observed in the Jewish samples. There was an interactive effect between ethnicity and the protective haplotype in CD (P = 0.04).

CONCLUSIONS

We observed a protective haplotype, consisting of the minor alleles for all 5 markers, to have a higher frequency in the non-Jewish controls than in CD and UC. Of further interest, the haplotype frequency was in the opposite direction in our Jewish case-control panels (both CD and UC), leading us to conclude 1) that TNFSF15 is indeed an IBD susceptibility gene, and 2) the disease susceptibility is ethnic-specific.

Evaluation of the interleukin-23 receptor gene coding variant R381Q in pediatric and adult Crohn disease

BACKGROUND

Pediatric-onset Crohn disease (CD) may differ in genotype or phenotype from adult-onset CD. Genome-wide screening recently identified a protective mutation (R381Q) in the interleukin-23 (IL-23) receptor gene located on chromosome 1. The aims of our study were to evaluate whether this mutation is associated with CD in our population and to find whether it may have an impact on age of onset or a specific location phenotype in a pediatric- and adult-onset CD population.

PATIENTS AND METHODS

A total of 438 individuals (143 with pediatric-onset CD [age <18 years], 139 with adult-onset CD, and 157 control subjects) evaluated for age at onset and disease location were genotyped for the R381Q mutation in the IL-23 receptor gene by pyrosequencing.

RESULTS

Mutant allele incidences were 5.7% in the normal cohort and only 2.28% in the CD cohort (P = 0.01). Carriers were found to constitute 8.9% of the normal cohort and only 4.6% of the CD cohort (P = 0.029). Homozygotes were found in only the control cohort. The mean age of onset for all of the patients with the mutation (including both age groups) was 17.8 +/- 6.1 years versus 21.3 +/- 12.4 years for patients without the mutation (P =0.08). The mutation was not associated with differences in sex, site of disease, or ethnicity. We did not find evidence of allelic interaction with CARD15.

CONCLUSIONS

We confirmed the findings that the IL-23 receptor gene coding variant allele R381Q appears to decrease susceptibility to CD in an Israeli Jewish population. We found a trend toward earlier age of onset, but no interactions with CARD15 or modifying effect on disease location.

Genetic susceptibility has a more important role in pediatric-onset Crohn's disease than in adult-onset Crohn's disease

BACKGROUND

Genetic susceptibility may play a more important role in the etiology of early-onset inflammatory bowel disease (IBD) than in late-onset IBD, and therefore pediatric-onset IBD patients can be expected to have a higher frequency of gene mutations. We aimed to determine genotypes and phenotypes of patients with pediatric-onset IBD, to compare them with those of patients with adult-onset IBD and with controls, and to identify genotype-phenotype associations.

METHODS

Polymorphisms R702W, G908R, and 3020insC of CARD15 (caspase activating recruitment domain 15); Asp299Gly and Thr399Ile of TLR4; -207G-->C, 1672C-->T (L503F), rs3792876, rs274551, rs272893, and rs273900 of SLC22A4/5; and 113G-->A as well as rs2289311, rs1270912, and rs2165047 of DLG5 (Drosophila discs large homologue 5) were assessed in 103 pediatric-onset and 696 adult-onset IBD patients. Phenotypic classification was based on disease localization and behavior.

RESULTS

Homozygosity for 3020insC in CARD15 was significantly higher in patients with pediatric-onset Crohn's disease (CD) than in patients with adult-onset CD (4.2% versus 0.6%, 95% confidence interval [CI] 1.2-42.0). Homozygosity for single-nucleotide polymorphism (SNP) rs3792876 in SLC22A4/5 was significantly higher in patients with pediatric-onset CD than in patients with adult-onset CD (6.1% versus 1.1%, P=0.02). Polymorphism 3020insC in CARD15 was associated with ileal involvement (1.9% versus 13.3%, CI 1.0-53.8) and a positive family history (6.1% versus 20%, CI 1.2-9.0). DLG5 SNP rs2165047 was significantly associated with perianal disease (50% versus 21.2%, CI 1.4-4).

CONCLUSIONS

Polymorphisms 3020insC in CARD15 and SNP rs3792876 in SLC22A4/5 occurred statistically significantly more often in patients with pediatric-onset CD than in patients with adult-onset CD. Polymorphisms 3020insC in CARD15 and SNP rs2165047 in DLG5 were associated with specific phenotypes in this pediatric-onset CD cohort.

Systematic association mapping identifies NELL1 as a novel IBD disease gene

Crohn disease (CD), a sub-entity of inflammatory bowel disease (IBD), is a complex polygenic disorder. Although recent studies have successfully identified CD-associated genetic variants, these susceptibility loci explain only a fraction of the heritability of the disease. Here, we report on a multi-stage genome-wide scan of 393 German CD cases and 399 controls. Among the 116,161 single-nucleotide polymorphisms tested, an association with the known CD susceptibility gene NOD2, the 5q31 haplotype, and the recently reported CD locus at 5p13.1 was confirmed. In addition, SNP rs1793004 in the gene encoding nel-like 1 precursor (NELL1, chromosome 11p15.1) showed a consistent disease-association in independent German population- and family-based samples (942 cases, 1082 controls, 375 trios). Subsequent fine mapping and replication in an independent sample of 454 French/Canadian CD trios supported the authenticity of the NELL1 association. Further confirmation in a large German ulcerative colitis (UC) sample indicated that NELL1 is a ubiquitous IBD susceptibility locus (combined p<10⁻⁶; OR = 1.66, 95% CI: 1.30–2.11). The novel 5p13.1 locus was also replicated in the French/Canadian sample and in an independent UK CD patient panel (453 cases, 521 controls, combined p<10⁻⁶ for SNP rs1992660). Several associations were replicated in at least one independent sample, point to an involvement of ITGB6 (upstream), GRM8 (downstream), OR5V1 (downstream), PPP3R2 (downstream), NM_152575 (upstream) and HNF4G (intron).

Identification of sex-specific associations between polymorphisms of the osteoprotegerin gene, TNFRSF11B, and Paget's disease of bone

We studied the role of TNFRSF11B polymorphisms on the risk to develop Paget's disease of bone in a Belgian study population. We observed no association in men, but a highly significant association was found in women, and this was confirmed in a population from the United Kingdom.

INTRODUCTION

Juvenile Paget's disease has been shown to be caused by mutations in TNFRSF11B encoding osteoprotegerin. Although mutations in this gene have never been found in patients with typical Paget's disease of bone (PDB), there are indications that polymorphisms in TNFRSF11B might contribute to the risk of developing PDB.

MATERIALS AND METHODS

We recruited a population of 131 Belgian patients with sporadic PDB and 171 Belgian controls. By means of the HapMap, we selected 17 SNPs that, in combination with four multimarker tests, contain most information on common genetic variation in TNFRSF11B. To replicate the findings observed in the Belgian study population, genotyping data of SNPs generated in a UK population were reanalyzed.

RESULTS

In our Belgian study population, associations were found for two SNPs (rs11573871, rs1485286) and for one multimarker test involving rs1032129. When subsequently analyzing men and women separately, these associations turned out to be driven by women (56 cases, 78 controls). In addition, three other tagSNPs turned out to be associated in women only. These were rs2073617 (C950T), rs6415470, and rs11573869. Reanalysis of genotyping data from a UK study population indicated that the associations found for C950T and C1181G were also exclusively driven by women (146 cases, 216 controls). Meta-analysis provided evidence for risk increasing effects of the T allele of C950T and the G allele of C1181G in the female population (p = 0.002 and 0.003, respectively). The haplotypes formed by the SNPs associated in the Belgian population were also distributed differentially between female cases and controls.

CONCLUSIONS

We showed for the first time that SNPs influencing the risk to develop PDB could be sex-specific. Further research is necessary to identify the causative variants in TNFRSF11B and to elucidate the molecular pathogenic mechanism.