Objective: To investigate the association between Trp2 allele polymorphism with degenerative disc disease (DDD) in a Chinese Han population.
Methods: A total of 125 DDD patients (58 males and 67 females, 51.8 +/- 7.6 years old), and 125 controls matched in sex and age (63 males and 62 females, 45.3 +/- 8.3 years old) were recruited in the case-control study. Their peripheral blood samples were collected for DNA isolation. Based on NCBI genebank, the corresponding single nucleotide polymorphisms (snp)-SNP1 (rs7533552) and SNP2 (rs2077871) were identified. Hardy-Weinberg equilibrium was analyzed both in case and control groups. Then the case group was classified into different clinical phenotypes according to severity of degeneration, sole or multi-disc degeneration and different affected discs. Genotyping of all selected SNPs was performed by SNP stream technology. The association analysis between phenotypes and SNPs was conducted. Pairwise linkage disequilibrium was calculated in control population using Haploview 4.0 software.
Results: SNP1 (rs7533552), SNP2 (rs2077871) and corresponding SNP of Trp2 allele were gentyped and both polymorphisms distributed in line with Hardy-Weinberg equilibrium in case and control groups. Allelic frequency of SNP1A, SNP1G, SNP2C and SNP2T (42%, 47%, 88% and 90% respectively) of case group were not significantly different from those of control group (48%, 53%, 88% and 10% respectively, all P > 0.05). Genotypic frequencies of SNP1AA, SNP1AG, SNP1GG, SNP2CC, SNP2CT and SNP2TT in case group were not significantly different from those of control group (all P > 0.05). However there was an association with genotypic frequencies of SNP2 and severity of disc degeneration (chi(2) = 6.920, P = 0.031).
Conclusion: Trp2 allele is one of risk factors for the development and severity of DDD in a Chinese Han population.