Impact of host genetics on gut microbiome: Take-home lessons from human and mouse studies

The intestinal microbiome has emerged as an important component involved in various diseases.Therefore,the interest in understanding the factors shaping its composition is growing.The gut microbiome,often defined as a complex trait,contains diverse components and its properties are determined by a combination of external and internal effects.Although much effort has been invested so far,it is still difficult to evaluate the extent to which human genetics shape the composition of the gut microbiota.However,in mouse studies,where the environmental factors are better controlled,the effect of the genetic background was significant.The purpose of this paper is to provide a current assessment of the role of human host genetics in shaping the gut microbiome composition.Despite the inconsistency of the reported results,it can be estimated that the genetic factor affects a portion of the microbiome.However,this effect is currently lower than the initial estimates,and it is difficult to separate the genetic influence from the environmental effect.Additionally,despite the differences between the microbial composition of humans and mice,results from mouse models can strengthen our knowledge of host genetics underlying the human gut microbial variation.

Micro-coevolution of host genetics with gut microbiome in three Chinese ethnic groups

Understanding the micro-coevolution of the human gut microbiome with host genetics is challenging but essential in both evolutionary and medical studies.To gain insight into the interactions between host genetic variation and the gut microbiome,we analyzed both the human genome and gut microbiome collected from a cohort of 190 students in the same boarding college and representing 3 ethnic groups,Uyghur,Kazakh,and Han Chinese.We found that differences in gut microbiome were greater between genetically distinct ethnic groups than those genetically closely related ones in taxonomic composition,functional composition,enterotype stratification,and microbiome genetic differentiation.We also observed considerable correlations between host genetic variants and the abundance of a subset of gut microbial species.Notably,interactions between gut microbiome species and host genetic variants might have coordinated effects on specific human phenotypes.Bacteroides ovatus,previously reported to modulate intestinal immunity,is significantly correlated with the host genetic variant rs12899811(meta-P=5.55×10^(-5)),which regulates the VPS33B expression in the colon,acting as a tumor suppressor of colorectal cancer.These results advance our understanding of the micro-coevolution of the human gut microbiome and their interactive effects with host genetic variation on phenotypic diversity.

Towards system genetics analysis of head and neck squamous cell carcinoma using the mouse model,cellular platform,and clinical human data

Head and neck squamous cell cancer(HNSCC)is a leading global malignancy.Every year,More than 830000 people are diagnosed with HNSCC globally,with more than 430000 fatalities.HNSCC is a deadly diverse malignancy with many tumor locations and biological characteristics.It originates from the squamous epithelium of the oral cavity,oropharynx,nasopharynx,larynx,and hypopharynx.The most frequently impacted regions are the tongue and larynx.Previous investigations have demonstrated the critical role of host genetic susceptibility in the progression of HNSCC.Despite the advances in our knowledge,the improved survival rate of HNSCC patients over the last 40 years has been limited.Failure to identify the molecular origins of development of HNSCC and the genetic basis of the disease and its biological heterogeneity impedes the development of new therapeutic methods.These results indicate a need to identify more genetic factors underlying this complex disease,which can be better used in early detection and prevention strategies.The lack of reliable animal models to investigate the underlying molecular processes is one of the most significant barriers to understanding HNSCC tumors.In this report,we explore and discuss potential research prospects utilizing the Collaborative Cross mouse model and crossing it to mice carrying single or double knockout genes(e.g.Smad 4 and P53 genes)to identify genetic factors affecting the development of this complex disease using genome-wide association studies,epigenetics,micro RNA,long noncoding RNA,lnc RNA,histone modifications,methylation,phosphorylation,and proteomics.

Cellular and molecular aspects of gastric cancer

Gastric cancer remains a global killer with a shifting burden from the developed to the developing world. The cancer develops along a multistage process that is defined by distinct histological and pathophysiological phases. Several genetic and epigenetic alterations mediate the transition from one stage to another and these include mutations in oncogenes, tumour suppressor genes and cell cycle and mismatch repair genes. The most significant advance in the fight against gastric caner came with the recognition of the role of Helicobacter pylori （H pylori） as the most important acquired aetiological agent for this cancer. Recent work has focussed on elucidating the complex host/microbial interactions that underlie the neoplastic process. There is now considerable insight into the pathogenesis of this cancer and the prospect of preventing and eradicating the disease has become a reality. Perhaps more importantly, the study of H pylori-induced gastric carcinogenesis offers a paradigm for understanding more complex human cancers. In this review, we examine the molecular and cellular events that underlie Hpyloriinduced gastric cancer.

Hepatitis C virus:Is it time to say goodbye yet? Perspectives and challenges for the next decade

The majority of individuals exposed to hepatitis C virus(HCV) establish a persistent infection,which is a leading cause of chronic liver disease,cirrhosis and hepatocellular carcinoma.Major progress has been made during the past twenty-five years in understanding the HCV life cycle and immune responses against HCV infection.Increasing evidence indicates that host genetic factors can significantly influence the outcome of HCV infection and the response to interferon alpha-based antiviral therapy.The arrival of highly effective and convenient treatment regimens for patients chronically infected with HCV has improved prospects for the eradication of HCV worldwide.Clinical trials are evaluating the best anti-viral drug combination,treatment doses and duration.The new treatments are better-tolerated and have shown success rates of more than 95%.However,the recent breakthrough in HCV treatment raises new questions and challenges,including the identification of HCVinfected patients and to link them to appropriate health care,the high pricing of HCV drugs,the emergence of drug resistance or naturally occurring polymorphism in HCV sequences which can compromise HCV treatment response.Finally,we still do not have a vaccine against HCV.In this concise review,we will highlight the progress made in understanding HCV infection and therapy.We will focus on the most significant unsolved problems and the key future challenges in the management of HCV infection.

Causal role of Helicobacter pylori infection in gastric cancer

Gastric cancer is the second most frequent cancer in the world, accounting for a large proportion of all cancer cases in Asia, Latin America, and some countries in Europe. Helicobacter pylori（H pylori） is regarded as playing a specific role in the development of atrophic gastritis, which represents the most recognized pathway in multistep intestinal-type gastric carcinogenesis. Recent studies suggest that a combination of host genetic factors, bacterial virulence factors, and environmental and lifestyle factors determine the severity of gastric damage and the eventual clinical outcome of H pylori infection. The seminal discovery of Hpylori as the leading cause of gastric cancer should lead to effective eradication strategies. Prevention of gastric cancer requires better screening strategies to identify candidates for eradication.

Role of bacterial and genetic factors in gastric cancer in Costa Rica

AIM： To evaluate several risk factors for gastric cancer （GC） in Costa Rican regions with contrasting GC incidence rate （GCIR）. METHODS： According to GCIR, 191 Helicobacter pylori （H pylori）-positive patients were classified into groups A （high GCIR, n = 101） and B （low GCIR, n = 90）. Human DNA obtained from biopsy specimens was used in the determination of polymorphisms of the genes coding for interleukin （IL）-1β and IL-10 by PCRRFLP, and IL-1RN by PCR. H pylori DNA extractions obtained from clinical isolates of 83 patients were used for PCR-based genotyping of H pylori cagA, vacA and babA2. Human DNA from gastric biopsies of 52 GC patients was utilized for comparative purposes. RESULTS： Cytokine polymorphisms showed no association with GCIR variability. However, gastric atrophy, intestinal metaplasia and strains with different vacA genotypes in the same stomach （mixed strain infection） were more frequently found in group A than in group B, and cagA and vacA s1b were significantly associated with high GCIR （P = 0.026 and 0.041, respectively）. IL- 1β＋3954_T/C （OR 2.1, 1.0-4.3）, IL-1RN^＊2/L （OR 3.5, 1.7-7.3） and IL-10-592_C/A （OR 3.2, 1.5-6.8） were individually associated with GC, and a combination of these cytokine polymorphisms with Hpylori vacA slb and ml further increased the risk （OR 7.2, 1.4-36.4）. CONCLUSION： Although a proinflammatory cytokine genetic profile showed an increased risk for developing GC, the characteristics of Hpylori infection, in particular the status of cagA and vacA genotype distribution seemed to play a major role in GCIR variability in Costa Rica.

Of genes and microbes： solving the intricacies in host genomes

Microbiome research is a quickly developing field in biomedical research, and we have witnessed its poten- tial in understanding the physiology, metabolism and immunology, its critical role in understanding the health and disease of the host, and its vast capacity in disease prediction, intervention and treatment. However, many of the fundamental questions still need to be addressed, including the shaping forces of microbial diversity between individuals and across time. Microbiome research falls into the classical nature vs. nurture sce- nario, such that host genetics shape part of the micro- biome, while environmental influences change the original course of microbiome development. In this review, we focus on the nature, i.e., the genetic part of the equation, and summarize the recent efforts in understanding which parts of the genome, especially the human and mouse genome, play important roles in determining the composition and functions of microbial communities, primarily in the gut but also on the skin. We aim to present an overview of different approaches in studying the intricate relationships between host genetic variations and microbes, its underlying philos- ophy and methodology, and we aim to highlight a few key discoveries along this exploration, as well as current pitfalls. More evidence and results will surely appear in upcoming studies, and the accumulating knowledge will lead to a deeper understanding of what we could finally term a ＂hologenome＂, that is, the orga- nized, closely interacting genome of the host and the microbiome.

Genome-Wide Association Study Reveals Host Genetic Factors for Liver Diseases

A number of disease-associated genetic markers for common liver diseases have been identified using genome-wide association studies (GWASs). The GWAS strategy is based on genome-wide single-nucleotide polymorphism typing technologies, which are now commercially available, accom-panied by statistical methods to identify host genetic factors that are associated with target diseases or complex genetic traits. One of the most striking features of the GWAS strategy is the ability to identify unexpected disease-associated genetic markers across the entire human genome. Here, we describe the technological aspects of the GWAS strategy with examples from actual GWAS reports related to hepatitis research, including drug response for patients with chronic hepatitis C, susceptibility to primary biliary cirrhosis, and hepatitis-B-related hepatocellular carcinoma.