Exome sequencing identifies DLG1 as a novel gene for potential susceptibility to Crohn's disease in a Chinese family study

In Vitro Models for Investigating Intestinal Host-Pathogen Interactions

Infectious diseases are increasingly recognized as a major threat worldwide due to the rise of antimicrobial resistance and the emergence of novel pathogens. In vitro models that can adequately mimic in vivo gastrointestinal physiology are in high demand to elucidate mechanisms behind pathogen infectivity, and to aid the design of effective preventive and therapeutic interventions. There exists a trade-off between simple and high throughput models and those that are more complex and physiologically relevant. The complexity of the model used shall be guided by the biological question to be addressed. This review provides an overview of the structure and function of the intestine and the models that are developed to emulate this. Conventional models are discussed in addition to emerging models which employ engineering principles to equip them with necessary advanced monitoring capabilities for intestinal host-pathogen interrogation. Limitations of current models and future perspectives on the field are presented.

Molecular Foundations of Inflammatory Diseases: Insights into Inflammation and Inflammasomes

Inflammatory diseases are a global health problem affecting millions of people with a wide range of conditions. These diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), osteoarthritis (OA), gout, and diabetes, impose a significant burden on patients and healthcare systems. A complicated interaction between genetic variables, environmental stimuli, and dysregulated immune responses shows the complex biological foundation of various diseases. This review focuses on the molecular mechanisms underlying inflammatory diseases, including the function of inflammasomes and inflammation. We investigate the impact of environmental and genetic factors on the progression of inflammatory diseases, explore the connection between inflammation and inflammasome activation, and examine the incidence of various inflammatory diseases in relation to inflammasomes.

A DLG1-ARHGAP31-CDC42 axis is essential for the intestinal stem cell response to fluctuating niche Wnt signaling

A central factor in the maintenance of tissue integrity is the response of stem cells to variations in the levels of niche signals. In the gut, intestinal stem cells (ISCs) depend on Wnt ligands for self-renewal and proliferation. Transient increases in Wnt signaling promote regeneration after injury or in inflammatory bowel diseases, whereas constitutive activation of this pathway leads to colorectal cancer. Here, we report that Discs large 1 (Dlg1), although dispensable for polarity and cellular turnover during intestinal homeostasis, is required for ISC survival in the context of increased Wnt signaling. RNA sequencing (RNA-seq) and genetic mouse models demonstrated that DLG1 regulates the cellular response to increased canonical Wnt ligands. This occurs via the transcriptional regulation of Arhgap31, a GTPase-activating protein that deactivates CDC42, an effector of the non-canonical Wnt pathway. These findings reveal a DLG1-ARHGAP31-CDC42 axis that is essential for the ISC response to increased niche Wnt signaling.

Polymorphisms of the TNF Gene and Three Susceptibility Loci Are Associated with Crohn's Disease and Perianal Fistula Crohn's Disease: A Study among the Han Population from South China

Background

Although 90 susceptibility loci of Crohn’s disease (CD) have been confirmed in the Asian population, susceptibility genes for perianal fistula of CD (pCD) in this population remain unknown. This study explored susceptibility genes for CD and pCD in the Han population from South China.

Material/Methods

In total, 490 patients diagnosed with CD between July 2012 and June 2016 at the Sixth Affiliated Hospital of Sun Yat-sen University were included and divided into the CD group (n=240) and the pCD group (n=250). The healthy control group was composed of 260 volunteers. Peripheral blood samples were taken, and single nucleotide polymorphism (SNP) locus sequencing was used to screen for susceptibility loci. SNPs were sequenced using matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

Results

Nine SNPs in TNFSF1 on chromosome 9 were associated with CD. Among them, the rs6478106 locus is a risk locus for CD. The distribution frequency of the T allele of the rs6478106 SNP was significantly different between cases and controls (32.49% versus 18.27%, P<0.001). Rs72553867, located in the IRGM gene on chromosome 5, rs4409764, located in the NKX2–3 gene on chromosome 10, and rs3731772, located in the AOX1 gene on chromosome 2, were susceptibility factors for pCD. Nine SNPs located in TNFSF15 on chromosome 9 were related to CD in Han individuals from Southern China.

Conclusions

The rs6478106 T allele is associated with the risk of CD in the investigated population. SNPs rs72553867 (IRGM gene), rs4409764 (NKX2–3 gene), and rs3731772 (AOX1 gene) increase the risk of pCD.

Genetic Studies of Inflammatory Bowel Disease-Focusing on Asian Patients

The pathogenesis of inflammatory bowel disease (IBD) is not well-understood; however, increased and persistent intestinal inflammation, due to inappropriate immune responses that are caused by interactions between genetic factors, gut microbiota, and environmental factors, are thought to lead to IBD. Various studies have identified more than 240 genetic variants related to IBD. These genetic variants are involved in innate and adaptive immunity, autophagy, defective bacterial handing, interleukin-23 and 10 signaling, and so on. According to several epidemiological and clinical studies, the phenotypes and clinical course of IBD differ between Asians and Europeans. Although the risk loci for IBD typically overlap between Asians and Westerners, genetic heterogeneity has been detected in many loci/genes, such as NOD2/CARD15, TNFSF15 and human leukocyte antigen, contributing to the risk of IBD. Thus, although common pathways exist between Westerners and Asians in the development of IBD, their significance may differ for individual pathways. Although genetic studies are not universally applicable in the clinical field, they may be useful for diagnosing and categorizing IBD, predicting therapeutic responses and toxicity to drugs, and assessing prognosis by risk modeling, thereby enabling precision medicine for individual patients.

Regulation of spermatid polarity by the actin- and microtubule (MT)-based cytoskeletons

It is conceivable that spermatid apico-basal polarity and spermatid planar cell polarity (PCP) are utmost important to support spermatogenesis. The orderly arrangement of developing germ cells in particular spermatids during spermiogenesis are essential to obtain structural and nutrient supports from the fixed number of Sertoli cells across the limited space of seminiferous epithelium in the tubules following Sertoli cell differentiation by ∼17 day postpartum (dpp) in rodents and ∼12 years of age at puberty in humans. Yet few studies are found in the literature to investigate the role of these proteins to support spermatogenesis. Herein, we briefly summarize recent findings in the field, in particular emerging evidence that supports the concept that apico-basal polarity and PCP are conferred by the corresponding polarity proteins through their effects on the actin- and microtubule (MT)-based cytoskeletons. While much research is needed to bridge our gaps of understanding cell polarity, cytoskeletal function, and signaling proteins, a critical evaluation of some latest findings as summarized herein provides some important and also thought-provoking concepts to design better functional experiments to address this important, yet largely expored, research topic.

Investigation of inflammatory bowel disease risk factors in 4 families in central China

The prevalence of inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is increasing markedly in China. The present study performed pedigree analysis of 4 families with a history of IBD and investigated the association of genetic and environmental factors with susceptibility to IBD. A total of 10 IBD patients (8 CD patients and 2 UC patients) and 90 family members were included in the present study. The clinical characteristics of familial subjects were compared with those of patients with sporadic IBD. Previously reported mutations, namely interleukin-10 receptor (IL10R)-A Thr84Ile, IL10RA Gly141Arg, IL10RB Trp159X, X-linked inhibitor of apoptosis (XIAP) Cys203Tyr, nucleotide-binding oligomerization domain-containing protein 2 (NOD2) Arg702Trp, NOD2 Gly908Arg and NOD2 Leu1007fsinsC, were screened in the patients with IBD, and selected demographic factors were compared between the patients and their unaffected family members. It was observed that single-gene and multi-gene inheritance patterns contributed to IBD in Chinese families. Based on data from the registry system, the ratio of patients with a family history of IBD was 1.25%, which was lower than that in the Western population. First-degree relatives were found to be more susceptible to IBD, and siblings were affected more frequently. Furthermore, the median age of diagnosis was younger in familial patients than in sporadic patients (29.0 vs. 36.0 for CD; 35.5 vs. 41.0 for UC). However, none of the 7 susceptibility loci were present in any of the familial patients. Immigration was a significant risk factor of IBD (odds ratio: 4.667; 95% confidence interval: 1.165-18.690; P=0.021). In conclusion, genetic heterogeneity exits between Chinese families with IBD and the Western population. The present findings suggest that genetic background and environmental factors serve a role in the pathogenesis of IBD.

Mechanisms of Cell Polarity-Controlled Epithelial Homeostasis and Immunity in the Intestine

Intestinal epithelial cell polarity is instrumental to maintain epithelial homeostasis and balance communications between the gut lumen and bodily tissue, thereby controlling the defense against gastrointestinal pathogens and maintenance of immune tolerance to commensal bacteria. In this review, we highlight recent advances with regard to the molecular mechanisms of cell polarity-controlled epithelial homeostasis and immunity in the human intestine.

The Same Intestinal Inflammatory Disease despite Different Genetic Risk Factors in the East and West?

Background

Inflammatory bowel disease (IBD) is a chronic inflammatory disease with unknown etiology. It is likely caused by a complex interplay between genetic, immunologic and environmental factors. Although IBD is still relatively uncommon in Asia, a multitude of studies have shown that it is an emerging disease around the world. Recent insights have highlighted both the similarities and differences amongst Asian and Western IBD patients.

Summary

The annual incidence of IBD in the East is still low compared with the West, but there are differences between different regions of Asia. Time trend studies have shown that the incidence of IBD is on the rise. Some notable differences in the clinical manifestations of IBD between the East and West have also been noted. 'Westernization' of lifestyle may encompass various social and environmental changes that account for the emergence of IBD in our population, although genetics also plays a role in disease pathogenesis. Diagnosis and treatment challenges include limited access to medical care in certain areas, limited availability and high cost of medications, lack of insurance reimbursement, paucity of multidisciplinary teams for the management of complicated IBD cases, and a high prevalence of endemic infections. Currently, the risk of colorectal cancer is lower in the East than in the West, but cancer rates will likely approach that of the West in the future as the prevalence of IBD continues to rise.

Key Messages

Measures to improve access to diagnostic tools, increase the availability of medication, and provide adequate multidisciplinary care for IBD patients will become increasingly important in Asia. Differences between the East and West will provide a unique opportunity for global collaboration in basic and clinical research to further our understanding of the disease entity and also provide more locoregional data to healthcare providers and policymakers to make informed decisions and policy changes when tackling the rising burden of IBD in Asia.

Gene Co-Expression Network Analysis for Identifying Modules and Functionally Enriched Pathways in Type 1 Diabetes

Type 1 diabetes (T1D) is a complex disease, caused by the autoimmune destruction of the insulin producing pancreatic beta cells, resulting in the body’s inability to produce insulin. While great efforts have been put into understanding the genetic and environmental factors that contribute to the etiology of the disease, the exact molecular mechanisms are still largely unknown. T1D is a heterogeneous disease, and previous research in this field is mainly focused on the analysis of single genes, or using traditional gene expression profiling, which generally does not reveal the functional context of a gene associated with a complex disorder. However, network-based analysis does take into account the interactions between the diabetes specific genes or proteins and contributes to new knowledge about disease modules, which in turn can be used for identification of potential new biomarkers for T1D. In this study, we analyzed public microarray data of T1D patients and healthy controls by applying a systems biology approach that combines network-based Weighted Gene Co-Expression Network Analysis (WGCNA) with functional enrichment analysis. Novel co-expression gene network modules associated with T1D were elucidated, which in turn provided a basis for the identification of potential pathways and biomarker genes that may be involved in development of T1D.

Risk Genes of Inflammatory Bowel Disease in Asia: What Are the Most Important Pathways Affected?

Genetic factors play an important role in the pathogenesis of inflammatory bowel disease (IBD), and IBD is now recognized as a complex disease that results from interplay between genetic and environment factors. To date, over 160 IBD-susceptible loci have been identified using genome-wide association studies (GWAS). The risk genes identified in these studies are involved in various pathways in innate and adaptive immune response such as innate bacterial sensing, autophagy and interleukin-23 receptor/T-helper cell 17 pathway. It was initially believed that the genetic backgrounds of Asian IBD patients differ from that of other populations. Recent GWAS and meta-analysis found that there is pervasive sharing of risk loci between the East and West. Overlapping risk genes between populations of different ancestries indicate that pathways underlying the etiology of IBD may be common between Asia and other areas. However, the importance of individual pathways may be different in Asia from the Western countries. Identifying the most important pathways affected in Asian IBD patients may provide a better understanding of pathogenesis of IBD in Asia and improve the clinical management of the patients.

Lessons learned--resolving the enigma of genetic factors in IBS

IBS is the most prevalent functional gastrointestinal disorder and phenotypically characterized by chronic abdominal discomfort, pain and altered defecation patterns. The pathophysiology of IBS is multifactorial, albeit with a substantial genetic component. To date, studies using various methodologies, ranging from family and twin studies to candidate gene approaches and genome-wide association studies, have identified several genetic variants in the context of IBS. Yet, despite enlarged sample sizes, increased statistical power and meta-analyses in the past 7 years, positive associations are still scarce and/or have not been reproduced. In addition, epigenetic and pharmacogenetic approaches remain in their infancy. A major hurdle is the lack of large homogenized case-control cohorts recruited according to standardized and harmonized criteria. The COST Action BM1106 GENIEUR (GENes in Irritable Bowel Syndrome Research Network EURope) has been established to address these obstacles. In this Review, the (epi)genetic working group of GENIEUR reports on the current state-of-the-art in the field, highlights fundamental flaws and pitfalls in current IBS (epi)genetic research and provides a vision on how to address and improve (epi)genetic approaches in this complex disorder in the future.

Genetics of inflammatory bowel disease from multifactorial to monogenic forms

Inflammatory bowel disease (IBD) is a group of chronic multifactorial disorders. According to a recent study, the number of IBD association loci is increased to 201, of which 37 and 27 loci contribute specifically to the development of Crohn’s disease and ulcerative colitis respectively. Some IBD associated genes are involved in innate immunity, in the autophagy and in the inflammatory response such as NOD2, ATG16L1 and IL23R, while other are implicated in immune mediated disease (STAT3) and in susceptibility to mycobacterium infection (IL12B). In case of early onset of IBD (VEO-IBD) within the 6^th year of age, the disease may be caused by mutations in genes responsible for severe monogenic disorders such as the primary immunodeficiency diseases. In this review we discuss how these monogenic disorders through different immune mechanisms can similarly be responsible of VEO-IBD phenotype. Moreover we would highlight how the identification of pathogenic genes by Next Generation Sequencing technologies can allow to obtain a rapid diagnosis and to apply specific therapies.

Emerging leadership lecture: Inflammatory bowel disease in Asia: emergence of a "Western" disease

More than a decade ago, inflammatory bowel disease (IBD) is rare in Asia. Today, the importance of IBD in Asia is exemplified by its rapidly increasing incidence, complicated disease behavior, and substantial morbidity. In the first large-scale population-based epidemiologic study in Asia, the incidence of IBD varied from 0.60 to 3.44 per 100,000. There has been a twofold to threefold increase in the incidence of IBD in several countries in Asia. Ulcerative colitis (UC) is more prevalent than Crohn's disease (CD), although CD incidence is rapidly increasing. A positive family history is much less common than in the West, as are extra-intestinal disease manifestations. Complicated and penetrating CD are common in Asia. These epidemiologic changes may relate to increased contact with the West, westernization of diet, improved hygiene, increasing antibiotics use, or changes in the gut microbiota. Asian patients with CD have altered gut microbiota compared with their healthy counterparts and Caucasian CD subjects. Mucosa-associated microbiota in IBD may differ geographically. In a population-based case-control study, breast-feeding, having pets, and better sanitary conditions were protective of IBD, suggesting that childhood environment plays an important role in modulating disease development. Genetic factors also differ between Asians and Caucasians. Nucleotide oligomerization domain-2 (NOD2) and autophagy variants were not associated with CD, but tumor necrosis factor superfamily gene-15 polymorphisms were strongly associated with CD in East Asians. Research in Asia, an area of rapidly changing IBD epidemiology, may lead to the discovery of critical etiologic factors that lead to the development of IBD.