Correlation Between TL1A Specific SNP And Inflammatory Bowel Disease

Background: Inflammatory Bowel Diseases(IBD),including ulcerative colitis(UC)and Krohn’s Disease(CD),are a group of chronic nonspecific inflammatory diseases involving the gastrointestinal tract.Environmental factors,genetic factors,gut microbiota,and immune response are four major factors involved in its pathogenesis.The risk polymorphism of tumor necrosis factor superfamily member15(TNFSF15)has been identified as associated with disease susceptibility and inflammation severity in European and American populations,as well as in East Asian populations such as Japan and South Korea.The coding product,tumor necrosis factor like ligand 1A(TL1A),is overexpressed in the intestinal inflammatory region of patients,It is more significant in patients carrying risk alleles.Single nucleotide polymorphism(SNP)is a common genetic factor that affects people’s susceptibility to diseases.SNPs located in the gene regulatory and coding regions directly affect gene expression mRNA and proteins,and can cause structural and functional changes.At present,research on IBD and TL1A in the Han Chinese population is still in its infancy.Objective: To study the polymorphism of three SNP loci rs6478106,rs6478109,and rs7848647 in the TL1A gene regulatory region in IBD patients and healthy individuals,as well as the differences in transmembrane mRNA and serum secretory protein expression levels.To evaluate the distribution characteristics of SNP in IBD and healthy individuals,analyze the correlation between TL1A expression and SNP and its clinical features,and the relationship between the occurrence and development of IBD,and provide theoretical basis and technical support for TL1A as a diagnostic or therapeutic target.Methods: 53 IBD patients and 126 healthy controls were collected from the Han population.The peripheral venous blood and serum of both patients were extracted.DNA in blood cells and RNA in peripheral blood mononuclear cell(PBMC)were extracted;The gene detection of target SNPs in the study population was carried out by PCR and sequencing technology,and the distribution of genotype and allele frequency of each SNP site was evaluated.The linkage disequilibrium status of related haplotypes was analyzed,and their correlation with TL1A expression was evaluated;QPCR was used to detect the relative expression level of transmembrane TL1A mRNA in PBMC,and ELISA was used to detect the expression level of serum TL1A protein.The expression differences,correlation,and diagnostic value of TL1A protein in different body states were compared;Analyze the correlation between different alleles of SNP loci,transmembrane TL1A mRNA levels,serum TL1A protein levels,age of onset of IBD,lesion site,disease behavior,and important inflammatory indicators such as hypersensitive C-reactive protein(CRP),erythrocyte sedimentation rate(ESR),fecal calprotectin,and other clinical features.Results:(1)There was no statistical difference in the distribution of three genotypes of TL1A gene rs6478106 and rs7848647 between IBD patients and healthy controls(P>0.05),and there was no statistical difference in the distribution of allele frequency between the two groups(P>0.05),suggesting that the above two loci were not related to the susceptibility to IBD;The distribution of allele T at the rs6478109 locus of TL1A gene in the CD and healthy control group showed statistical differences(P=0.048),indicating that the T locus is a risk factor for CD and is associated with CD susceptibility;(2)The rs6478109 and rs7848647 loci of the TL1A gene are located close to each other on the chromosome at a distance of 280 bp,and there is a strong linkage imbalance between the two loci.In IBD patients,the linkage imbalance coefficient |D ′ |=1,while in the healthy control group,the linkage imbalance coefficient |D′|=0.927.In IBD patients,the main haplotypes G/T/A at the rs6478106,rs6478109,and rs7848647 closely related to the high expression of transmembrane TL1A in PBMC(P=0.033);(3)The relative expression level of transmembrane TL1A mRNA in the IBD group was 2.927 times higher than that in the healthy control group.The TT genotype at rs6478109 and the AA genotype at rs7848647 were associated with higher transmembrane TL1A mRNA levels(P=0.041);(4)There is no correlation between serum TL1A protein expression levels and transmembrane TL1A mRNA levels in IBD and healthy individuals(P>0.05);(5)There was a positive correlation between transmembrane TL1A mRNA levels and ESR,fecal calprotectin levels in the IBD population and healthy individuals(P=0.0437,r=0.4802;P=0.0468,r=0.5595).There was no statistical difference between the two groups in terms of neutrophil percentage,interleukin-6,and CRP levels(P>0.05).There was a positive correlation between transmembrane TL1A mRNA levels and the percentage of NK like T cells(P=0.0055,r=0.6780),while there was a positive correlation between the percentage of NK like cells,the absolute value of T lymphocytes,and the percentage of NK like cells There was no statistical difference in the absolute value of B lymphocytes(P>0.05);(6)Among the collected patients,there was no statistically significant difference(P>0.05)between the genotypes and alleles of rs6478106,rs6478109,rs7848647 loci and the characteristics of CD disease(age of onset,lesion site,disease behavior,perianal lesions,disease activity).There was no statistically significant difference(P>0.05)between the genotypes and alleles of these loci and the characteristics of UC disease(age of onset,lesion site,disease activity).Conclusion:(1)The rs6478109 polymorphism in the TL1A gene regulatory region is associated with CD susceptibility,and the secondary allele T is a genetic factor for CD risk;(2)There is a strong linkage imbalance at the rs6478109 and rs7848647 loci of the TL1A gene.In IBD patients,the main haplotypes G/T/A at the rs6478106,rs6478109,and rs7848647 loci of the TL1A gene are closely related to the high expression of transmembrane TL1A in PBMC;(3)The levels of PBMC transmembrane TL1A mRNA in IBD patients were significantly higher than those in healthy controls.The expression was particularly elevated in CD patients carrying rs6478106 GG,rs6478109 TT,and rs7848647 AA,and was associated with the severity of intestinal inflammation.The PBMC transmembrane TL1A mRNA level is expected to become a new biological marker for IBD.