AIF-1 gene does not confer susceptibility to Behçet's disease: Analysis of extended haplotypes in Sardinian population.

Sara Lai,Maria Maddalena Angioni,Alessandro Mathieu,Gian Luca Erre,Rosa Sorrentino,Maria Teresa Fiorillo,Alberto Floris,Carlo Carcassi,Matteo Piga,Giuseppe Passiu,Alberto Cauli,Fabiana Paladini

doi:10.1371/journal.pone.0204250

Abstract

BackgroundBehçet’s disease (BD) is a polygenic immune-mediated disorder characterized by a close association with the HLA-B*51 allele. The HLA region has a strong linkage disequilibrium (LD) and carries several genetic variants (e.g. MIC-A, TNF-α genes) identified as associated to BD because of their LD with HLA-B*51. In fact, the HLA-B*51 is inherited as part of extended HLA haplotypes which are well preserved in patients with BD. Sardinian population is highly differentiated from other Mediterranean populations because of a distinctive genetic structure with very highly preserved HLA haplotypes.Patients and methodsIn order to identify other genes of susceptibility to BD within the HLA region we investigated the distribution of human Allograft Inflammatory Factor-1 (AIF-1) gene variants among BD patients and healthy controls from Sardinia. Six (rs2736182; rs2259571; rs2269475; rs2857597; rs13195276; rs4711274) AIF-1 single nucleotide polymorphisms (SNPs) and related extended haplotypes have been investigated as well as their LD within the HLA region and with HLA-B*51. Overall, 64 BD patients, 43 HLA-B*51 positive healthy controls (HC) and 70 random HC were enrolled in the study.ResultsHLA-B*51 was the only allele with significantly higher frequency (pc = 0.0021) in BD patients (40.6%) than in HC (9.8%). The rs2259571T AIF-1 variant had a significantly reduced phenotypic, but not allelic frequency in BD patients (72.1%; pc = 0.014) compared to healthy population (91.3%). That was likely due to the LD between HLA-B*51 and rs2259571G (pc = 9E-5), even though the rs2259571G distribution did not significantly differ between BD patients and HC.ConclusionNo significant difference in distribution of AIF-1 SNPs haplotypes was observed between BD patients and HC and between HLA-B*51 positive BD patients and HLA-B*51 positive HC. Taken together, these results suggest that AIF-1 gene is not associated with susceptibility to BD in Sardinia.

Highlights

Behcet’s disease (BD) is a chronic vasculitis characterized by recurrent oral ulcers, genital ulcers, ocular and skin manifestations with involvement of arteries and veins of all sizes
In order to identify other genes of susceptibility to BD within the HLA region we investigated the distribution of human Allograft Inflammatory Factor-1 (AIF-1) gene variants among BD patients and healthy controls from Sardinia
HLA-B*51 was the only allele with significantly higher frequency in BD patients (40.6%) than in healthy controls (HC) (9.8%)

Summary

Introduction

Behcet’s disease (BD) is a chronic vasculitis characterized by recurrent oral ulcers, genital ulcers, ocular and skin manifestations with involvement of arteries and veins of all sizes. BD clusters in an area between latitudes 30 ̊ N and 45 ̊ N spanning from the far Eastern Asia to the Mediterranean basin [1,2] Such a distinctive clustering seems related to geographical distribution of genetic susceptibility factors among general population [3,4]. Genome wide association studies (GWAS) identified a strong association between BD and the HLA region comprehensive of HLA-BÃ51 within an extended haplotype [9]. These findings were suggestive of the presence of additional genes within the HLA region conferring susceptibility to BD. Sardinian population is highly differentiated from other Mediterranean populations because of a distinctive genetic structure with very highly preserved HLA haplotypes

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