Study of APOE Gene and D2S439 Marker in Patients of Rheumatoid Arthritis and their Correlation with Severity of Disease: A Case Control Study.

ABSTRACT

AIM: To delineate the genetic differences in polymorphism of the APOE and D2S439 marker genes for patients with and without rheumatoid arthritis and to study the distribution frequency of the prevalent alleles of these genes in clinically defined sub groups of patients/controls of Indian origin, specifically and their correlation with severity of disease using DAS score. MATERIAL AND METHODS: This is a case control study where peripheral blood samples 160 cases and 150 controls were collected. RESULTS: We evaluated the association of the tetra nucleotide repeat microsatellite marker D2S439 lying at 231.27cM position on the q arm of chromosome-2. The alleles of this marker ranged in size from 163bp-203bp in PCR product length corresponding to 5-15 (CTAT)n tetra repeats. The allele frequencies for this marker in the North Indian population are different from the CEPH populations. The longer alleles, >199bp (=14 or 15 CTAT repeats) were not observed. The genotypes after bimodal distribution differ significantly among cases and controls (p=0.003). Statistically significant difference was seen between cases and controls for ≥(CTAT) 10 longer allele which was more prevalent in the adult RA cases than in controls. Severity of RA was defined by a DAS28 score of >6 on a scale of ten. No significant association was seen with the APOE polymorphism and disease severity. CONCLUSION: The long allele of D2S439 marker representing an expansion of the CTAT, tetranucleotide repeat doubles an individual's the risk for developing RA.