Abstract

Introduction: Leukocyte immunoglobulin-like receptor A3 (LILRA3) belongs to the LILR family with unique feature of a 6.7-kb deletion variation among individuals. Frequencies of the 6.7-kb deletion vary widely across populations, but so far it has not been carefully investigated among Han Chinese subpopulations. Furthermore, we previously identified the non-deleted (functional) LILRA3 as a novel genetic risk for multiple autoimmune diseases. The current study aimed to investigate (i) whether frequencies of the LILRA3 6.7-kb deletion differ within Han Chinese subpopulations and (ii) whether the functional LILRA3 is a novel genetic risk for ankylosing spondylitis (AS).Methods: The LILRA3 6.7-kb deletion was genotyped in two independent cohorts, including 1,567 subjects from Shenzhen Hospital and 2,507 subjects from People’s Hospital of Peking University. Frequencies of the 6.7-kb deletion were first investigated in combined healthy cohort according to the Chinese administrative district divisions. Association analyses were performed on whole dataset and subsets according to the geographic regions. Impact of the functional LILRA3 on AS disease activity was evaluated.Results: Frequencies of LILRA3 6.7-kb deletion were highly differentiated within Han Chinese subpopulations, being gradually decreased from Northeast (80.6%) to South (47.4%). Functional LILRA3 seemed to be a strong genetic risk in susceptibility to AS under almost all the alternative genetic models, if the study subjects were not geographically stratified. However, stratification analysis revealed that the functional LILRA3 was consistently associated with AS susceptibility mainly in Northern Han subgroup under the alternative genetic models, but not in Central and Southern Hans. Functional LILRA3 conferred an increased disease activity in AS patients (P < 0.0001 both for CRP and ESR, and P = 0.003 for BASDAI).Conclusions: The present study is the first to report that the frequencies of LILRA3 6.7-kb deletion vary among Chinese Hans across geographic regions. The functional LILRA3 is associated with AS susceptibility mainly in Northern Han, but not in Central and Southern Han subgroups. Our finding provides new evidence that LILRA3 is a common genetic risk for multiple autoimmune diseases and highlights the genetic differentiation among different ethnicities, even within the subpopulations of an ethnic group.

Highlights

  • Leukocyte immunoglobulin-like receptor A3 (LILRA3) belongs to the LILR family with unique feature of a 6.7-kb deletion variation among individuals

  • Frequencies of LILRA3 6.7-kb Deletion Are Highly Differentiated Within Han Chinese Subpopulations

  • As the frequencies of LILRA3 6.7-kb deletion were highly different in different populations worldwide and the study subjects were came from multiple geographical regions across China in present study, we hypothesize that the frequencies of LILRA3 6.7-kb deletion may vary among Chinese Hans

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Summary

Introduction

Leukocyte immunoglobulin-like receptor A3 (LILRA3) belongs to the LILR family with unique feature of a 6.7-kb deletion variation among individuals. Frequencies of the 6.7-kb deletion vary widely across populations, but so far it has not been carefully investigated among Han Chinese subpopulations. We previously identified the non-deleted (functional) LILRA3 as a novel genetic risk for multiple autoimmune diseases. The current study aimed to investigate (i) whether frequencies of the LILRA3 6.7-kb deletion differ within Han Chinese subpopulations and (ii) whether the functional LILRA3 is a novel genetic risk for ankylosing spondylitis (AS). Ankylosing spondylitis (AS) is a chronic autoimmune disease characterized by new bone formation, progressively leading to ankylosis of the axial skeleton and functional disability. The genome-wide association studies (GWAS) have revealed that more than 60 additional genetic risk factors contributed to the disease, indicating a polygenic nature of AS. Only approximately 30% of AS heritability has been explained by the known genetic loci; many remain unidentified (reviewed in (Li and Brown, 2017; Ranganathan et al, 2017))

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