Polymorphisms in the Tlr4 and Tlr5 Gene Are Significantly Associated with Inflammatory Bowel Disease in German Shepherd Dogs

Aarti Kathrani,Angela Murphy,Dirk Werling,Brian Catchpole,Alex German,Arthur House,Karin Allenspach,Holger K Eltzschig

doi:10.1371/journal.pone.0015740

Aarti Kathrani, Angela Murphy + Show 6 more

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https://doi.org/10.1371/journal.pone.0015740

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Abstract

Inflammatory bowel disease (IBD) is considered to be the most common cause of vomiting and diarrhoea in dogs, and the German shepherd dog (GSD) is particularly susceptible. The exact aetiology of IBD is unknown, however associations have been identified between specific single-nucleotide polymorphisms (SNPs) in Toll-like receptors (TLRs) and human IBD. However, to date, no genetic studies have been undertaken in canine IBD. The aim of this study was to investigate whether polymorphisms in canine TLR 2, 4 and 5 genes are associated with IBD in GSDs. Mutational analysis of TLR2, TLR4 and TLR5 was performed in 10 unrelated GSDs with IBD. Four non-synonymous SNPs (T23C, G1039A, A1571T and G1807A) were identified in the TLR4 gene, and three non-synonymous SNPs (G22A, C100T and T1844C) were identified in the TLR5 gene. The non-synonymous SNPs identified in TLR4 and TLR5 were evaluated further in a case-control study using a SNaPSHOT multiplex reaction. Sequencing information from 55 unrelated GSDs with IBD were compared to a control group consisting of 61 unrelated GSDs. The G22A SNP in TLR5 was significantly associated with IBD in GSDs, whereas the remaining two SNPs were found to be significantly protective for IBD. Furthermore, the two SNPs in TLR4 (A1571T and G1807A) were in complete linkage disequilibrium, and were also significantly associated with IBD. The TLR5 risk haplotype (ACC) without the two associated TLR4 SNP alleles was significantly associated with IBD, however the presence of the two TLR4 SNP risk alleles without the TLR5 risk haplotype was not statistically associated with IBD. Our study suggests that the three TLR5 SNPs and two TLR4 SNPs; A1571T and G1807A could play a role in the pathogenesis of IBD in GSDs. Further studies are required to confirm the functional importance of these polymorphisms in the pathogenesis of this disease.

Highlights

The healthy gut is able to regulate inflammatory responses to commensal bacteria and food antigens whilst maintaining the capacity to respond to pathogens [1,2,3]
We show that the TLR5 G22A, C100T, T1844C and the TLR4 single nucleotide polymorphisms (SNPs) A1571T and G1807A SNPs are significantly associated with inflammatory bowel disease (IBD) in German shepherd dog (GSD)
Four non-synonymous SNPs were identified in the TLR4 exons; T23C (ENSCAFT00000005653), G1039A, A1571T (ENSCAFT00000005653) and G1807A (ENSCAFT00000005653) and three non-synonymous SNPs were identified in the TLR5 exon; G22A (ENSCAFT00000018059), C100T (ENSCAFT00000018059) and T1844C (ENSCAFT00000018059)

Summary

Introduction

The healthy gut is able to regulate inflammatory responses to commensal bacteria and food antigens whilst maintaining the capacity to respond to pathogens [1,2,3]. This distinction relies on Toll-like receptors (TLRs) which are ideally situated on intestinal epithelia cells and recognise microbe associated molecular patterns (MAMPs) [4]. IBD is a chronic debilitating disease and occurs in both people and dogs. Inflammation associated with CD can occur in any area of the intestinal tract, the terminal ileum is most commonly affected, whereas UC is confined to the colon [6]. Immunosupressive therapy is the mainstay treatment for both human IBD and canine IBD patients [5,6]

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