Aberrant DNA methylation and
expression of ERAP1 gene in ankylosing spondylitis
Running title: ERAP1 methylation in AS
Authors: Yubo Ma a,b, MM, Dazhi Fanc, MM, Shanshan Xua,b,MM, Jixiang
Deng a,b, MM, Xing Gao a,b, MM, Xu
Zhang a,b, MD, Faming Pan a,b,#, MD
Affiliations: a Department of Epidemiology and Biostatistics,
School of Public Health, Anhui Medical University, Hefei, Anhui, China;
b The Key Laboratory of Major Autoimmune Diseases, Anhui Medical
University, 81 Meishan Road, Hefei, Anhui, China; c Foshan Institute of
Fetal Medicine, Southern Medical University Affiliated Maternal and
Child Health Hospital of Foshan, Foshan, Guangdong, China.
Corresponding Author: Faming Pan, Department of Epidemiology
and Biostatistics, School of Public Health, Anhui Medical University,
Hefei, Anhui, China. E-mail:famingpan@ahmu.edu.cn
Key words: ankylosing
spondylitis; DNA methylation; ERAP1; mRNA
Abbreviations: AS: ankylosing spondylitis; AUC: area under
curve; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index;
BASFI: Bath Ankylosing Spondylitis Functional Index; CI: confidence
interval; CpG: cytosine-guanine dinucleotide; CRP: C-reactive protein;
ERAP1: endoplasmic reticulum aminopeptidase 1; ESR: erythrocyte
sedimentation rate; EWAS: epigenome-wide association study; HLA: human
leukocyte antigen; OR: odds ratio; PCR: polymerase chain reaction; ROC:
Receiver operating characteristic; NSAIDs: Non-steroidal
anti-inflammatory drugs.
Summary
Objective : Endoplasmic reticulum aminopeptidase 1 (ERAP1) is
known to participate in the pathogenesis of ankylosing spondylitis (AS)
cooperated with HLA-B27. This study aimed to evaluate the relationship
between promoter methylation and
mRNA levels of ERAP1 and AS.
Methods : The DNA methylation level of 100 AS patients and 100
health controls (HCs) were tested using targeted bisulfite sequencing
assay. Besides, the mRNA level of 20 AS patients and HCs was measured
used quantitative real-time reverse transcription-polymerase chain
reaction to verify the results of DNA methylation.
Results : The methylation levels of two CpG islands containing
31 loci in ERAP1 promoter were measured. ERAP1_1 (P< 0.001) and ERAP1_2 (P < 0.001) islands
were significantly hyperrmethylated in AS patients compared with healthy
controls. Correspondingly, the mRNA level was significantly lower in AS
patients. The ROC curve analysis reported the sensitivity, specificity
and area under curve were 0.717, 0.737 and 0.779 of differential
methylated CpG loci of ERAP1 for AS diagnosis. Besides, we also
found that the methylation level was associated with the family history,
non-steroidal anti-inflammatory drugs use, X-ray classification and
clinical manifestations.
Conclusions : Our study demonstrated that the ERAP1 gene
is significantly hypermethylated in AS patients, which is
verified
by the lower mRNA level of AS patients. Our findings suggested that
aberrant methylation of ERAP1 promoter may take part in the
pathogenesis of AS and can be considered as diagnostic tool and
therapeutic target of AS.