RESEARCH ARTICLES Association of ERAP1 Allelic Variants with

ABSTRACT Ankylosing spondylitis (AS) belongs to a group of autoimmune diseases affecting the axial skeleton. Beside the hla-b*27 allele, several other human genes that control the variety processes of immune homeostasis are considered to be associated with AS manifestation in different human populations. Among strong associated non-MHC genes erap1 encoding the endoplasmic reticulum aminopeptidase 1 isoform was recently identified by single nucleotide poly-morphisms (SNPs) meta analysis. In our study we inspected the genetic association of five non-synonymous coding SNPs from erap1 with AS in Caucasians. We implemented the SSP-PCR system for precise genotyping of 87 hla-b*27 positive AS patients and 77 hla-b*27 healthy donors from the Russian population. Considerable differences in allele’s frequencies within patients vs control cohort were shown for 3 of 5 SNPs under investigation. Using the EM-algorhitm we reconstructed 3-marker haplotypes that distinguish with high probability two cohorts due to differences in the haplotypes frequencies. In such a way both the sensitive, CCT, haplotype and the protective, TTC, one were predicted. To verify the calculation we determined genuine frequencies of 5-marker haplotypes in AS cohort by haplotyping of individual cDNA samples using improved SSP-PCR primer set. We demonstrated that the frequencies of in silica re-constucted haplotypes and the frequencies of experimentally detected haplotypes are in a good agreement. Frequency of the risk haplotype CCT (rs17482078/10050860/2287987) detected within AS cohort reaches 88%, as well as the frequency calculated by EM-algorhitm