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Association analysis of the vitamin D receptor gene, the type I collagen gene COL1A1, and the estrogen receptor gene in idiopathic osteoarthritis.

OBJECTIVE
Evidence has accumulated supporting a role for genes in the etiology of osteoarthritis (OA). Several candidates have been targeted as potential susceptibility loci including genes that are involved in the regulation of bone density. Genetic association analysis has suggested a role for the vitamin D receptor gene (VDR) and the estrogen receptor gene (ER) in susceptibility. Such findings must be tested in additional independent cohorts. We tested for association of these 2 genes, plus a third gene implicated in bone density, COL1A1, with idiopathic OA.


METHODS
A case-control cohort of 371 affected probands and 369 unaffected spouses was used. Association was tested using 4 intragenic single nucleotide polymorphisms (SNP), one each for the VDR and COL1A1 genes, and 2 for the ER gene. The VDR and ER SNP are the same SNP that have been associated with OA. All 4 SNP affect restriction enzyme sites and were genotyped using polymerase chain reaction and enzyme digestion. Allele and genotype distributions for each SNP were compared between cases and controls and analyzed using Fisher's exact test.


RESULTS
There was no evidence of association of the VDR or the ER gene SNP to OA. There was weak evidence of association of the COL1A1 SNP in female cases (p = 0.017), reflected by a difference in the distribution of genotypes at this SNP between female cases and controls (p = 0.027). However, when corrected for multiple testing, these results were not significant.


CONCLUSION
If the VDR, ER, or COL1A1 genes do encode predisposition to OA then the 4 SNP tested are not associated with major susceptibility alleles at these 3 loci.