The association of IL7RA gene polymorphism rs6897932 with Multiple Sclerosis in the northwestern population of Iran

Abstract

Multiple Sclerosis (MS) is a neuroinflammatory disorder affecting the central nervous system (CNS). It could present various types of symptoms, such as sensory, visual, or motor disturbances. It is more prevalent in females, and about 2.5 million people worldwide suffer from this disease. Various environmental and genetic factors could influence the incidence of this disease. In addition to major histocompatibility complex (MHC) genes which are the most associated genetic factor of MS, other non-MHC genes such as the receptor of interleukin 7 and 2 are involved in the physiopathology of the disease. The rs6897932 is a single nucleotide polymorphism of interleukin 7 receptor alpha (IL7-RA), widely known as a risk factor of MS. Our study aims to explore the association of this SNP with MS in the northwestern population of Iran for the first time. Materials and Methods: 45 MS cases and 45 age and gender-matched healthy subjects were sampled, and after meeting the inclusion and exclusion criteria were entered the study. The clinical data of patients, including the age of onset, the type of MS, familial history of MS, the primary presenting symptoms, Expanded Disability Status Scale (EDSS) score, and the time of the last relapse, were collected by interviewing and examining them. A 5ml peripheral venous blood sample was collected from each of the cases and controls. The Rapid Genomic DNA Extraction (RDGE) method extracted the genomic DNA after the Peripheral Blood Mononuclear Colony (PBMC) isolation. The High-Resolution Melting (HRM) method was used to determine the genotype of the samples. The collected data were statistically analyzed by the SPSS 25.0. Results: There was no difference between the cases and controls considering age and gender (31females and 14 males in each group, mean age:34). Forty-three patients had remitting relapsing MS (RRMS), and 2 cases had secondary progressive MS (SPMS). The median age of onset was 26, and the median EDSS score was 3. The Sensory (66.6%) and visual (60%) symptoms were the most common primary presenting of disease. The frequency of the C allele was 83.3% and 67.7% in cases and controls, respectively. The C allele was significantly associated with MS with an odds ratio of 2.37 (95%CI:1.17-4.83, P-value:0.015). The codominant and dominant models of inheritance could significantly explain the association. The CC genotype was significantly more prevalent in the cases than controls (OR:2.76).