Association of FCGR2A, JAK2 or HNF4A variants with ulcerative colitis in Koreans

Investigating the shared genetic basis of inflammatory bowel disease and systemic lupus erythematosus using genetic overlap analysis

BACKGROUND

Inflammatory bowel disease (IBD) and systemic lupus erythematosus (SLE) are autoimmune diseases that often coexist clinically. This phenomenon might be due to shared genetic components.

METHODS

Genome-wide association study (GWAS) data for IBD and SLE were analyzed to determine both global and local genetic correlations using three methodologies: linkage disequilibrium score regression (LDSC), genetic covariance analyzer (GNOVA), and SUPERGNOVA. The genetic overlap and risk loci were subsequently examined using the conditional/conjunctional false discovery rate (cond/conjFDR) statistical framework. Furthermore, a multi-trait analysis of MTAG was employed to validate the loci, followed by an LDSC analysis focusing on tissue-specific gene expression.

RESULTS

GWAS findings demonstrated a marked global genetic correlation between IBD (including Crohn's disease and ulcerative colitis) and SLE. Locally, SLE showed a strong association with IBD and Crohn's disease on chromosomes 10, 19, and 22. ConjFDR analysis confirmed the genetic overlap and identified relevant genetic risk loci. MTAG further validated several shared susceptibility genes. Additionally, the LDSC-SEG analysis results indicate that IBD (including CD and UC) and SLE are jointly enriched in the tissues of Spleen and Whole Blood.

CONCLUSION

This study confirms a genetic overlap between IBD and SLE, identifying marked comorbid genes and offering new insights for treating these diseases.

Evaluating the causal effect of circulating proteome on the risk of inflammatory bowel disease-related traits using Mendelian randomization

Objective

This study sought to identify circulating proteins causally linked to Inflammatory Bowel Disease (IBD) traits through a Mendelian Randomization (MR) analytical framework.

Methods

Using a large-scale, two-sample MR approach, we estimated the genetic links of numerous plasma proteins with IBD and its subtypes, leveraging information from the Inflammatory Bowel Disease Genetics Consortium. To assess the robustness of MR findings, methods like Bayesian colocalization, and Steiger filtering analysis, evaluation of protein-altering variants. Further insights into IBD's underlying mechanisms and therapeutic targets were gleaned from single-cell sequencing analyses, protein-protein interaction assessments, pathway enrichment analyses, and evaluation of drug targets.

Results

By cis-only MR analysis, we identified 83 protein-phenotype associations involving 27 different proteins associated with at least one IBD subtype. Among these proteins, DAG1, IL10, IL12B, IL23R, MST1, STAT3 and TNFRSF6B showed overlapping positive or negative associations in all IBD phenotypes. Extending to cis + trans MR analysis, we further identified 117 protein-feature associations, including 44 unique proteins, most of which were not detected in the cis-only analysis. In addition, by performing co-localization analysis and Steiger filtering analysis on the prioritized associations, we further confirmed the causal relationship between these proteins and the IBD phenotype and verified the exact causal direction from the protein to the IBD-related feature.

Conclusion

MR analysis facilitated the identification of numerous circulating proteins associated with IBD traits, unveiling protein-mediated mechanisms and promising therapeutic targets.

Multiple roles and regulatory mechanisms of the transcription factor HNF4 in the intestine

Hepatocyte nuclear factor 4-alpha (HNF4α) drives a complex array of transcriptional programs across multiple organs. Beyond its previously documented function in the liver, HNF4α has crucial roles in the kidney, intestine, and pancreas. In the intestine, a multitude of functions have been attributed to HNF4 and its accessory transcription factors, including but not limited to, intestinal maturation, differentiation, regeneration, and stem cell renewal. Functional redundancy between HNF4α and its intestine-restricted paralog HNF4γ, and co-regulation with other transcription factors drive these functions. Dysregulated expression of HNF4 results in a wide range of disease manifestations, including the development of a chronic inflammatory state in the intestine. In this review, we focus on the multiple molecular mechanisms of HNF4 in the intestine and explore translational opportunities. We aim to introduce new perspectives in understanding intestinal genetics and the complexity of gastrointestinal disorders through the lens of HNF4 transcription factors.

JAK-STAT signaling pathway-related gene single nucleotide polymorphisms and susceptibility to ankylosing spondylitis in eastern Chinese Han population

OBJECTIVE

A case-control study was utilized to investigate the relationship between genetic variation of JAK-STAT signaling pathway-related genes and the susceptibility to ankylosing spondylitis (AS).

METHODS

Fifteen SNPs in the JAK-STAT signaling pathway-related genes from 660 AS patients and 646 healthy controls were genotyped using iMLDR technology (JAK1: rs2230587, rs2230588, rs2780815, rs310241; JAK2: rs2274472, rs2230722, rs2230724, rs10758669; STAT1: rs10199181, rs1547550, rs2066802, rs45463799, rs6718902; STAT3: rs3744483; STAT5A: rs1135669).

RESULTS

Allele analysis revealed that the T allele of STAT1 rs6718902 was a protective agent for male AS patients (OR = 0.765, 95% CI = 0.644-0.909). Inheritance models showed that GG + CG as well as GG genotypes of STAT1 rs1547550 had a significant risk of developing AS in males (OR = 5.374, 95%CI = 2.505-11.526; OR = 5.186, 95%CI = 2.412-11.153). The TT + CT and TT genotypes at STAT1 rs6718902 were observed to be associated with a significantly decreased risk of AS compared to CC genotypes among male patients and male controls (OR = 0.637, 95%CI = 0.485-0.837; OR = 0.597, 95%CI = 0.422-0.845). Furthermore, the genotypes of JAK1 gene rs2230588, rs2780815, and rs310241 were correlated with the severity of clinical conditions in female AS patients, while the JAK2 rs2230724 genotypes may affect disease ability in male AS patients.

CONCLUSION

These findings indicated that JAK-STAT signaling pathway-related gene single nucleotide polymorphisms may be associated with AS susceptibility in eastern Chinese Han population. Key Points • The T allele of rs6718902 on the STAT1 gene may be a protective agent for male AS patients. • STAT1 rs1547550 GG + CG and GG genotypes were observed to be connected with a risk of male AS patients. However, STAT1 rs6718902 TT + CT and TT genotypes reduced the susceptibility risk of male AS patients compared to wild-type CC. • The JAK1 genes rs2230588, rs2780815, and rs310241 may affect disease functional status in female AS patients, while the JAK2 rs2230724 genotype was related to disease activity in male AS patients.

Unilateral panuveitis secondary to JAK2 mutation-associated lymphoproliferative disease

A woman in her 70s experienced painless vision loss in the right eye for 1 month. Acute retinal necrosis-induced panuveitis was the referral diagnosis. With dense vitreous haze, a vitrectomy was performed for vitreous biopsy followed by multimodal imaging. Vitreous biopsy yielded negative PCR results for herpes viruses and only inflammatory cells. Post-vitrectomy imaging showed involuted but pervasive pigmentary foci in the outer retina and the retinal pigment epithelium. Concurrently, peripheral blood showed pancytosis with giant platelets and a Janus kinase 2 (JAK2) mutation, which prompted a haematological evaluation. CT and MRI revealed a right frontal lobe intra-axial mass, diagnosed as diffuse large B cell lymphoma (DLBCL). Subsequently, bone marrow aspirate confirmed the pathogenic V617F JAK2 mutation. Following chemotherapy, the patient achieved lymphoma regression and uveitic quiescence. This is the first case report of acute unilateral panuveitis in a patient with JAK2 mutation and DLBCL but without evidence of intraocular involvement.

Transcriptional Integration of Distinct Microbial and Nutritional Signals by the Small Intestinal Epithelium

BACKGROUND & AIMS

The intestine constantly interprets and adapts to complex combinations of dietary and microbial stimuli. However, the transcriptional strategies by which the intestinal epithelium integrates these coincident sources of information remain unresolved. We recently found that microbiota colonization suppresses epithelial activity of hepatocyte nuclear factor 4 nuclear receptor transcription factors, but their integrative regulation was unknown.

METHODS

We compared adult mice reared germ-free or conventionalized with a microbiota either fed normally or after a single high-fat meal. Preparations of unsorted jejunal intestinal epithelial cells were queried using lipidomics and genome-wide assays for RNA sequencing and ChIP sequencing for the activating histone mark H3K27ac and hepatocyte nuclear factor 4 alpha.

RESULTS

Analysis of lipid classes, genes, and regulatory regions identified distinct nutritional and microbial responses but also simultaneous influence of both stimuli. H3K27ac sites preferentially increased by high-fat meal in the presence of microbes neighbor lipid anabolism and proliferation genes, were previously identified intestinal stem cell regulatory regions, and were not hepatocyte nuclear factor 4 alpha targets. In contrast, H3K27ac sites preferentially increased by high-fat meal in the absence of microbes neighbor targets of the energy homeostasis regulator peroxisome proliferator activated receptor alpha, neighbored fatty acid oxidation genes, were previously identified enterocyte regulatory regions, and were hepatocyte factor 4 alpha bound.

CONCLUSIONS

Hepatocyte factor 4 alpha supports a differentiated enterocyte and fatty acid oxidation program in germ-free mice, and that suppression of hepatocyte factor 4 alpha by the combination of microbes and high-fat meal may result in preferential activation of intestinal epithelial cell proliferation programs. This identifies potential transcriptional mechanisms for intestinal adaptation to multiple signals and how microbiota may modulate intestinal lipid absorption, epithelial cell renewal, and systemic energy balance.

Slc26a3 (DRA) in the Gut: Expression, Function, Regulation, Role in Infectious Diarrhea and Inflammatory Bowel Disease

BACKGROUND

The transport of transepithelial Cl- and HCO3- is crucial for the function of the intestinal epithelium and maintains the acid-based homeostasis. Slc26a3 (DRA), as a key chloride-bicarbonate exchanger protein in the intestinal epithelial luminal membrane, participates in the electroneutral NaCl absorption of intestine, together with Na+/H+ exchangers. Increasing recent evidence supports the essential role of decreased DRA function or expression in infectious diarrhea and inflammatory bowel disease (IBD).

METHOD

In this review, we give an overview of the current knowledge of Slc26a3, including its cloning and expression, function, roles in infectious diarrhea and IBD, and mechanisms of actions. A better understanding of the physiological and pathophysiological relevance of Slc26a3 in infectious diarrhea and IBD may reveal novel targets for future therapy.

CONCLUSION

Understanding the physiological function, regulatory interactions, and the potential mechanisms of Slc26a3 in the pathophysiology of infectious diarrhea and IBD will define novel therapeutic approaches in future.

Cinnamaldehyde and hesperetin attenuate TNBS-induced ulcerative colitis in rats through modulation of the JAk2/STAT3/SOCS3 pathway

Ulcerative colitis is an autoimmune inflammatory disorder with a negative impact on the life quality of patients. Cinnamaldehyde and hesperetin were chosen due to their antioxidants and anti-inflammatory effects. This study explored the protective effects of cinnamaldehyde (40 and 90 mg/kg, po) and hesperetin (50 and 100 mg/kg, po) on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced ulcerative colitis in rats. Cinnamaldehyde and hesperetin significantly improved macroscopic and histopathological examinations with a significant reduction in myeloperoxidase and intracellular adhesion molecule-1 expression. They significantly reduced colon oxidative stress by a significant elevation in both reduced glutathione content and superoxide dismutase activity with a significant reduction of NO content. Furthermore, cinnamaldehyde and hesperetin alleviated the inflammatory injury by a significant reduction in interleukin-6 along with suppression of nuclear factor-κB, receptor for advanced glycation end products, and tumor necrosis factor-α expression. Moreover, cinnamaldehyde and hesperetin significantly decreased p-JAK2 and p-STAT3 while significantly increased suppressors of cytokine signaling 3 (SOCS3) protein expression. In conclusion, cinnamaldehyde and hesperetin counteracted TNBS-induced ulcerative colitis through antioxidant, anti-inflammatory properties as well as modulation of the JAk2/STAT3/SOCS3 pathway.

Differential regulation of JAK/STAT-signaling in patients with ulcerative colitis and Crohn’s disease

In 2018, the pan-Janus kinase (JAK) inhibitor tofacitinib was launched for the treatment of ulcerative colitis (UC). Although tofacitinib has proven efficacious in patients with active UC, it failed in patients with Crohn’s disease (CD). This finding strongly hints at a different contribution of JAK signaling in both entities. Here, we review the current knowledge on the interplay between the JAK/signal transducer and activator of transcription (STAT) pathway and inflammatory bowel diseases (IBD). In particular, we provide a detailed overview of the differences and similarities of JAK/STAT-signaling in UC and CD, highlight the impact of the JAK/STAT pathway in experimental colitis models and summarize the published evidence on JAK/STAT-signaling in immune cells of IBD as well as the genetic association between the JAK/STAT pathway and IBD. Finally, we describe novel treatment strategies targeting JAK/STAT inhibition in UC and CD and comment on the limitations and challenges of the new drug class.

Anti-commensal IgG Drives Intestinal Inflammation and Type 17 Immunity in Ulcerative Colitis

Inflammatory bowel disease is a chronic, relapsing condition with two subtypes, Crohn's disease (CD) and ulcerative colitis (UC). Genome-wide association studies (GWASs) in UC implicate a FCGR2A variant that alters the binding affinity of the antibody receptor it encodes, FcγRIIA, for immunoglobulin G (IgG). Here, we aimed to understand the mechanisms whereby changes in FcγRIIA affinity would affect inflammation in an IgA-dominated organ. We found a profound induction of anti-commensal IgG and a concomitant increase in activating FcγR signaling in the colonic mucosa of UC patients. Commensal-IgG immune complexes engaged gut-resident FcγR-expressing macrophages, inducing NLRP3- and reactive-oxygen-species-dependent production of interleukin-1β (IL-1β) and neutrophil-recruiting chemokines. These responses were modulated by the FCGR2A genotype. In vivo manipulation of macrophage FcγR signal strength in a mouse model of UC determined the magnitude of intestinal inflammation and IL-1β-dependent type 17 immunity. The identification of an important contribution of IgG-FcγR-dependent inflammation to UC has therapeutic implications.

IgG and Fcγ Receptors in Intestinal Immunity and Inflammation

Fcγ receptors (FcγR) are cell surface glycoproteins that mediate cellular effector functions of immunoglobulin G (IgG) antibodies. Genetic variation in FcγR genes can influence susceptibility to a variety of antibody-mediated autoimmune and inflammatory disorders, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). More recently, however, genetic studies have implicated altered FcγR signaling in the pathogenesis of inflammatory bowel disease (IBD), a condition classically associated with dysregulated innate and T cell immunity. Specifically, a variant of the activating receptor, FcγRIIA, with low affinity for IgG, confers protection against the development of ulcerative colitis, a subset of IBD, leading to a re-evaluation of the role of IgG and FcγRs in gastrointestinal tract immunity, an organ system traditionally associated with IgA. In this review, we summarize our current understanding of IgG and FcγR function at this unique host-environment interface, from the pathogenesis of colitis and defense against enteropathogens, its contribution to maternal-fetal cross-talk and susceptibility to cancer. Finally, we discuss the therapeutic implications of this information, both in terms of how FcγR signaling pathways may be targeted for the treatment of IBD and how FcγR engagement may influence the efficacy of therapeutic monoclonal antibodies in IBD.

A Case-Control Study on Association of Ulcerative Colitis with FCGR2A Gene Polymorphisms in Chinese Patients

BACKGROUND AND AIMS

The Fc gamma receptor IIa (FcγRIIa), encoded by FCGR2A gene, has been suggested to play a crucial role in immunity by linking immunoglobulin G antibody-mediated responses with cellular effector and regulatory functions. Polymorphisms in FCGR2A have been shown to affect FcγRIIa/antibody interactions and have been potentially implicated in several autoimmune and inflammatory conditions. This study was designed to analyze the association between ulcerative colitis (UC) and FCGR2A polymorphisms in the Chinese population.

MATERIALS AND METHODS

A total of 422 patients with UC and 710 unaffected controls were recruited. Five single nucleotide polymorphisms of FCGR2A (rs1801274, rs10800309, rs4657039, rs511278, and rs6696854) were genotyped by SNaPshot. Analyses for linkage disequilibrium (LD) and haplotype studies of FCGR2A were performed for all study subjects.

RESULTS

The frequency of the minor homozygote (CC) of the rs1801274 SNP of FCGR2A was shown to be significantly lower in patients with UC than in controls (7.1% vs. 12.1%, p = 0.008). Two haplotype blocks, formed by FCGR2A (rs4657039, rs6696854, and rs10800309) and FCGR2A (rs1801274 and rs511278), respectively, were observed in the subsequent LD analysis. The TC haplotype constructed by the major allele of FCGR2A (rs1801274 and rs511278) was more prevalent in UC patients compared with controls (65.2% vs. 60.2%, p = 0.017).

CONCLUSIONS

The minor homozygote (CC) of FCGR2A (rs1801274) may contribute to decrease the susceptibility to UC and the TC haplotype formed by FCGR2A (rs1801274 and rs511278) may increase the risk of UC in the Chinese population.

Association of ulcerative colitis with solute-linked carrier family 26 member A3 gene polymorphisms and its expression in colonic tissues in Chinese patients

PURPOSE

Abnormalities of the solute-linked carrier family 26 member A3 (SLC26A3) are implicated in the pathogenesis of several diseases including ulcerative colitis (UC). The short communication aimed at investigating the associations of UC with SLC26A3 (rs17154444, rs7810937, rs7785539, rs2108225 and rs6951457) polymorphisms and its expression in colonic tissues.

METHODS

The techniques of SNaPshot method, quantitative real-time PCR and immunohistochemical analysis were conducted.

RESULTS AND CONCLUSION

We found that the rs2108225 variation in SLC26A3 might increase the risk of UC and affect its expression at both the mRNA and protein levels in colonic tissues of patients with UC. Moreover, the rs17154444 variation might influence the severity of UC.

Identification of key genes in non‑alcoholic fatty liver disease progression based on bioinformatics analysis

Due to economic development and lifestyle changes, the incidence of non-alcoholic fatty liver disease (NAFLD) has gradually increased in recent years. However, the pathogenesis of NAFLD is not yet fully understood. To identify candidate genes that contribute to the development and progression of NAFLD, two microarray datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified and functional enrichment analyses were performed. A protein-protein interaction network was constructed and modules were extracted using the Search Tool for the Retrieval of Interacting Genes and Cytoscape. The enriched functions and pathways of the DEGs included ‘cellular macromolecule biosynthetic process’, ‘cellular response to chemical stimulus’, ‘extracellular matrix organization’, ‘metabolic pathways’, ‘insulin resistance’ and ‘forkhead box protein O1 signaling pathway’. The DEGs, including type-1 angiotensin II receptor, formin-binding protein 1-like, RNA-binding protein with serine-rich domain 1, Ras-related C3 botulinum toxin substrate 1 and polyubiquitin-C, were identified using multiple bioinformatics methods and validated in vitro with reverse transcription-quantitative polymerase chain reaction analysis. In conclusion, five hub genes were identified in the present study, and they may aid in understanding of the molecular mechanisms underlying the development and progression of NAFLD.

Association of FCGR2A rs1801274 polymorphism with susceptibility to autoimmune diseases: A meta-analysis

OBJECTIVES

The aim of this meta-analysis was to estimate the association between the FCGR2A rs1801274 polymorphism and the susceptibility to autoimmune diseases more precisely.

METHODS

A meta-analysis was conducted on the association between the FCGR2A gene variants and ADs by allelic contrast, homozygote contrast, the recessive model, and the dominant model.

RESULTS

A total of 17 studies with 30 comparisons in different populations and genotype-methods were available for this meta-analysis, including 10 Kawasaki disease (KD), 7 Ulcerative colitis (UC), 6 Crohn's disease (CD), 3 Rheumatoid arthritis (RA), 2 Systemic lupus erythematosus (SLE), 1 Autoimmune thyroid disease (ATD) and 1 diabetes mellitus type 1 (T1D). A significant association between FCGR2A rs1801274 polymorphism were found in KD (OR = 1.409, P < 0.001) and UC (OR = 1.237, P < 0.001). A overall meta-analysis increased risk of AD significant association between FCGR2A rs1801274 gene polymorphism and ADs under allelic (OR = 1.378, P=0.000), homozygous (OR: 1.866, P=0.001), dominant (OR = 1.667, P = 0.000) and recessive (OR = 1.434, P=0.000) in Asian population. Meanwhile, a decreased risk of AD was detected in the allelic (OR= 0.882, P = 0.011), homozygous (OR = 0.777, P = 0.013), dominant (OR = 0.850, P = 0.032) and recessive (OR = 0.840, P = 0.048) in African-American population.

CONCLUSIONS

This meta-analysis demonstrates that the FCGR2A rs1801274 G-allele confers susceptibility to KD and UC. Data also suggests that the FCGR2A rs1801274 polymorphism may be associated with the susceptibility of multiple ADs in Asian and African-American populations.

Lack of Association between Genetic Polymorphisms of JAK-STAT Signaling Pathway Genes and Acute Anterior Uveitis in Han Chinese

Purpose. This study aimed to investigate the association between single nucleotide polymorphisms (SNPs) of JAK-STAT signaling pathway genes and acute anterior uveitis (AAU) with or without ankylosing spondylitis (AS) in the Han Chinese population. Methods. Eleven SNPs of the JAK1, JAK2, STAT1, IRF1, and NOS2 genes were analyzed in 443 AAU patients with AS, 486 AAU patients without AS, and 714 healthy controls. Genotyping was performed by PCR-RFLP assay or TaqMan® probe assay. The Chi-squared (χ²) test and multivariate logistic regression analysis were used to compare the distributions of alleles and genotypes between patients and controls. P values were adjusted using Bonferroni correction. Results. We did not observe significant differences in the genotype and allele frequencies of any SNP between AAU patients with or without AS and healthy controls. Stratification analyses by gender and HLA-B27 status showed a boundary significant association between two SNPs (rs10975003 and rs10758669) in JAK2 and AAU (P = 0.052 and P = 0.053, resp.). Conclusions. Our results indicated that genetic polymorphisms of the JAK-STAT signaling pathway genes may not be associated with AAU in the Han Chinese population.

Genetic characteristics of inflammatory bowel disease in a Japanese population

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are two major forms of inflammatory bowel disease (IBD). Meta-analyses of genome-wide association studies (GWAS) have identified 163 susceptibility loci for IBD among European populations; however, there is limited information for IBD susceptibility in a Japanese population.

METHODS

We performed a GWAS using imputed genotypes of 743 IBD patients (372 with CD and 371 with UC) and 3321 controls. Using 100 tag single-nucleotide polymorphisms (SNPs) (P < 5 × 10(-5)), a replication study was conducted with an independent set of 1310 IBD patients (949 with CD and 361 with UC) and 4163 controls. In addition, 163 SNPs identified by a European IBD GWAS were genotyped, and genetic backgrounds were compared between the Japanese and European populations.

RESULTS

In the IBD GWAS, two East Asia-specific IBD susceptibility loci were identified in the Japanese population: ATG16L2-FCHSD2 and SLC25A15-ELF1-WBP4. Among 163 reported SNPs in European IBD patients, significant associations were confirmed in 18 (8 CD-specific, 4 UC-specific, and 6 IBD-shared). In Japanese CD patients, genes in the Th17-IL23 pathway showed stronger genetic effects, whereas the association of genes in the autophagy pathway was limited. The association of genes in the epithelial barrier and the Th17-IL23R pathways were similar in the Japanese and European UC populations.

CONCLUSIONS

We confirmed two IBD susceptibility loci as common for CD and UC, and East Asian-specific. The genetic architecture in UC appeared to be similar between Europeans and East Asians, but may have some differences in CD.

Genes involved in the regulation of intestinal permeability and their role in ulcerative colitis

OBJECTIVE

Genome-wide association studies have identified single nucleotide polymorphisms in genes that might influence intestinal barrier function (HNF4A, ECM1, CDH1 and LAMB1) to increase the risk for ulcerative colitis (UC). The aim of our study was to detect causative sequence alterations and provide a functional link to a disturbed intestinal permeability (IP) in UC.

METHODS

A total of 19 UC patients with increased IP (lactulose/mannitol ratio measured by sugar drink test) were identified from a large database, and exon/intron boundaries, coding and promoter regions of HNF4A, ECM1, CDH1 and LAMB1 were sequenced. Variants with putative protein alterations were studied for an association with IP in 82 UC patients. A case-control analysis including a genotype phenotype correlation was performed in 743 patients with inflammatory bowel disease (IBD) and 473 healthy controls.

RESULTS

In UC patients, we identified 11 missense-mutations, 12 synonymous mutations, one putative promoter variant and three variants in introns close to the intron/exon boundaries (CDH1, HNF4A). For several variants prediction tools revealed damaging protein alterations. None of the studied variants, however, showed an association with an increased IP in UC. In the case-control analysis, the frequency of all investigated variants did not differ between UC or Crohn's disease and healthy controls. Furthermore, no significant association was found to a distinct phenotype.

CONCLUSIONS

Despite our large sequencing approach, we could not identify protein altering variants in the genes HNF4A, ECM1, CDH1 and LAMB1 which could explain an impaired intestinal barrier function in UC. The functional relevance of these genes in IBD remains unknown.

Congenital chloride-losing diarrhea in a Mexican child with the novel homozygous SLC26A3 mutation G393W

Congenital chloride diarrhea is an autosomal recessive disease caused by mutations in the intestinal lumenal membrane Cl⁻/HCO⁻₃ exchanger, SLC26A3. We report here the novel SLC26A3 mutation G393W in a Mexican child, the first such report in a patient from Central America. SLC26A3 G393W expression in Xenopus oocytes exhibits a mild hypomorphic phenotype, with normal surface expression and moderately reduced anion transport function. However, expression of HA-SLC26A3 in HEK-293 cells reveals intracellular retention and greatly decreased steady-state levels of the mutant polypeptide, in contrast to peripheral membrane expression of the wildtype protein. Whereas wildtype HA-SLC26A3 is apically localized in polarized monolayers of filter-grown MDCK cells and Caco2 cells, mutant HA-SLC26A3 G393W exhibits decreased total polypeptide abundance, with reduced or absent surface expression and sparse punctate (or absent) intracellular distribution. The WT protein is similarly localized in LLC-PK1 cells, but the mutant fails to accumulate to detectable levels. We conclude that the chloride-losing diarrhea phenotype associated with homozygous expression of SLC26A3 G393W likely reflects lack of apical surface expression in enterocytes, secondary to combined abnormalities in polypeptide trafficking and stability. Future progress in development of general or target-specific folding chaperonins and correctors may hold promise for pharmacological rescue of this and similar genetic defects in membrane protein targeting.

JAK2 rs10758669 polymorphisms and susceptibility to ulcerative colitis and Crohn's disease: a meta-analysis

In this meta-analysis, we aimed to clarify the impact of Janus kinase 2 (JAK2) rs10758669 polymorphisms on ulcerative colitis (UC) and Crohn's disease (CD) risk. Data were extracted, and pooled odd ratios (ORs) as well as 95% confidence intervals (95%CIs) were calculated. Eleven studies with 7009 CD patients, 7929 UC patients, and 19235 controls were included. The results showed that JAK2 rs10758669 polymorphism was associated with CD (AC vs. AA, OR = 1.16, 95%CI, 1.08-1.24; CC vs. AA, OR = 1.29, 95%CI, 1.17-1.43; AC + CC vs. AA, OR = 1.19, 95%CI, 1.11-1.27; CC vs. AA + AC, OR = 1.19, 95%CI, 1.09-1.31; C vs. A, OR = 1.14, 95%CI, 1.09-1.20) and UC susceptibility (AC vs. AA, OR = 1.14, 95%CI, 1.06-1.22; CC vs. AA, OR = 1.33, 95%CI, 1.20-1.47; AC + CC vs. AA, OR = 1.18, 95%CI, 1.10-1.27; CC vs. AA + AC, OR = 1.24, 95%CI, 1.12-1.36; C vs. A, OR = 1.15, 95%CI, 1.10-1.21). But no significant association was found between JAK2 rs10758669 polymorphism with CD in Asian. Either in adult-onset group or multi-age group, hospital-based group or population-based group, JAK2 rs10758669 polymorphism was associated with CD and UC susceptibility. This meta-analysis indicated that JAK2 rs10758669 polymorphism was a risk factor both for CD and UC, especially in Caucasian. The differences in age of onset and study design did not influence the associations obviously. Gene-gene and gene-environment interactions should be investigated in the future.

Probiotic Bifidobacterium species stimulate human SLC26A3 gene function and expression in intestinal epithelial cells

SLC26A3, or downregulated in adenoma (DRA), plays a major role in mediating Cl(-) absorption in the mammalian intestine. Disturbances in DRA function and expression have been implicated in intestinal disorders such as congenital Cl(-) diarrhea and gut inflammation. We previously showed that an increase in DRA function and expression by Lactobacillus acidophilus and its culture supernatant (CS) might underlie antidiarrheal effects of this probiotic strain. However, the effects of Bifidobacterium species, important inhabitants of the human colon, on intestinal Cl(-)/HCO3 (-) exchange activity are not known. Our current results demonstrate that CS derived from Bifidobacterium breve, Bifidobacterium infantis, and Bifidobacterium bifidum increased anion exchange activity in Caco-2 cells (∼1.8- to 2.4-fold). Consistent with the increase in DRA function, CS also increased the protein, as well as the mRNA, level of DRA (but not putative anion transporter 1). CS of all three Bifidobacterium sp. increased DRA promoter activity (-1,183/+114 bp) in Caco-2 cells (1.5- to 1.8-fold). Furthermore, the increase in DRA mRNA expression by CS of B. breve and B. infantis was blocked in the presence of the transcription inhibitor actinomycin D (5 μM) and the ERK1/2 MAPK pathway inhibitor U0126 (10 μM). Administration of live B. breve, B. infantis, and B. bifidum by oral gavage to mice for 24 h increased DRA mRNA and protein levels in the colon. These data demonstrate an upregulation of DRA via activation of the ERK1/2 pathway that may underlie potential antidiarrheal effects of Bifidobacterium sp.

Genetic update on inflammatory factors in ulcerative colitis: Review of the current literature

Ulcerative colitis (UC) is one of the main types of inflammatory bowel disease, which is caused by dysregulated immune responses in genetically predisposed individuals. Several genetic factors, including interleukin and interleukin receptor gene polymorphisms and other inflammation-related genes play central role in mediating and modulating the inflammation in the human body, thereby these can be the main cause of development of the disease. It is clear these data are very important for understanding the base of the disease, especially in terms of clinical utility and validity, but summarized literature is exiguous for challenge health specialist that can used in the clinical practice nowadays. This review summarizes the current literature on inflammation-related genetic polymorphisms which are associated with UC. We performed an electronic search of Pubmed Database among publications of the last 10 years, using the following medical subject heading terms: UC, ulcerative colitis, inflammation, genes, polymorphisms, and susceptibility.

Chromatin profiling reveals regulatory network shifts and a protective role for hepatocyte nuclear factor 4α during colitis

Transcriptional regulatory mechanisms likely contribute to the etiology of inflammatory bowel disease (IBD), as genetic variants associated with the disease are disproportionately found at regulatory elements. However, the transcription factors regulating colonic inflammation are unclear. To identify these transcription factors, we mapped epigenomic changes in the colonic epithelium upon inflammation. Epigenetic marks at transcriptional regulatory elements responded dynamically to inflammation and indicated a shift in epithelial transcriptional factor networks. Active enhancer chromatin structure at regulatory regions bound by the transcription factor hepatocyte nuclear factor 4α (HNF4A) was reduced during colitis. In agreement, upon an inflammatory stimulus, HNF4A was downregulated and showed a reduced ability to bind chromatin. Genetic variants that confer a predisposition to IBD map to HNF4A binding sites in the human colon cell line CaCo2, suggesting impaired HNF4A binding could underlie genetic susceptibility to IBD. Despite reduced HNF4A binding during inflammation, a temporal knockout model revealed HNF4A still actively protects against inflammatory phenotypes and promotes immune regulatory gene expression in the inflamed colonic epithelium. These findings highlight the potential for HNF4A agonists as IBD therapeutics.

The SLC26 gene family of anion transporters and channels

The phylogenetically ancient SLC26 gene family encodes multifunctional anion exchangers and anion channels transporting a broad range of substrates, including Cl(-), HCO3(-), sulfate, oxalate, I(-), and formate. SLC26 polypeptides are characterized by N-terminal cytoplasmic domains, 10-14 hydrophobic transmembrane spans, and C-terminal cytoplasmic STAS domains, and appear to be homo-oligomeric. SLC26-related SulP proteins of marine bacteria likely transport HCO3(-) as part of oceanic carbon fixation. SulP genes present in antibiotic operons may provide sulfate for antibiotic biosynthetic pathways. SLC26-related Sultr proteins transport sulfate in unicellular eukaryotes and in plants. Mutations in three human SLC26 genes are associated with congenital or early onset Mendelian diseases: chondrodysplasias for SLC26A2, chloride diarrhea for SLC26A3, and deafness with enlargement of the vestibular aqueduct for SLC26A4. Additional disease phenotypes evident only in mouse knockout models include oxalate urolithiasis for Slc26a6 and Slc26a1, non-syndromic deafness for Slc26a5, gastric hypochlorhydria for Slc26a7 and Slc26a9, distal renal tubular acidosis for Slc26a7, and male infertility for Slc26a8. STAS domains are required for cell surface expression of SLC26 proteins, and contribute to regulation of the cystic fibrosis transmembrane regulator in complex, cell- and tissue-specific ways. The protein interactomes of SLC26 polypeptides are under active investigation.

Genome-wide association study of ulcerative colitis in Koreans suggests extensive overlapping of genetic susceptibility with Caucasians

BACKGROUND

Recent genome-wide association studies and meta-analyses have identified 47 susceptibility loci for ulcerative colitis (UC) in Caucasian populations. A previous genome-wide association study of UC in a Japanese population suggested marginal sharing of susceptibility loci between Caucasian and Asian populations. We performed a genome-wide association studies to identify UC susceptibility loci in a Korean population and further comparative study.

METHODS

We analyzed 581,060 autosomal single-nucleotide polymorphisms (SNPs) in 388 individuals with UC and 739 control subjects in the discovery stage. For the validation, 64 suggestive SNPs were analyzed in an additional 417 affected individuals and 732 control subjects.

RESULTS

Three genetic loci were validated for significant association, and all were previously reported in Caucasians including the major histocompatibility complex region (top SNP, rs9271366; P = 1.03 × 10(-18), odds ratio [OR] = 2.10), 16q24.1 (rs16940186; P = 4.39 × 10(-10), OR = 1.56), and RNF186-OTUD3-PLA2G2E at chromosome arm 1p36.13 (top SNP, rs4654903 in OTUD3; P = 7.43 × 10(-9), OR = 0.64). Although failed to reach genome-wide statistical significance, 2 additional loci previously reported in Caucasians including rs17085007 at chromosome arm 13q12 and JAK2 at chromosome arm 9p24 were significant after Bonferroni correction (P(corrected) = 0.0016 and P(corrected) = 0.0056, respectively). FOS, UBE2L3, the JAK2 gene region, and rs1297265 at chromosome arm 21q21.1 likely play a role in both Crohn's disease and UC.

CONCLUSIONS

Our data support the biologic significance of the overlapping loci for UC between Caucasian and Korean populations. Our data suggest that genetic associations for UC tend to overlap more extensively among different ethnic groups than those for Crohn's disease, which shows well-established dependence on ethnicity.