The association between ANKH promoter polymorphism and chondrocalcinosis is independent of age and osteoarthritis: results of a case-control study.
BACKGROUND
Chondrocalcinosis (CC) most commonly results from calcium pyrophosphate crystal deposition (CPPD). The objective of this study is to examine the association between candidate single-nucleotide polymorphisms (SNPs) and radiographic CC.


METHODS
SNPs in ankylosis human (ANKH), high ferritin (HFE), tissue non-specific alkaline phosphatase (TNAP), ecto-neucleotide pyrophosphatase 1 (ENPP1), and transferrin (TE) genes were genotyped in participants of the Genetics of Osteoarthritis and Lifestyle (GOAL) and Nottingham Osteoarthritis Case-Control studies. Adjusted genotype odds ratio (aORGENOTYPE), the OR for association between one additional minor allele and CC, was calculated and adjusted for age, gender, body mass index (BMI), and osteoarthritis (OA) by using binary logistic regression. Statistical significance was set at P ≤0.003 after Bonferroni correction for multiple tests.


RESULTS
The -4bpG > A polymorphism in the 5' untranslated region (5' UTR) of ANKH associated with CC after Bonferroni correction. This was independent of age, gender, OA, and BMI; aORGENOTYPE (95% confidence interval, or CI) was 1.39 (1.14-1.69) (P = 0.001). rs3045 and rs875525, two other SNPs in ANKH, associated with CC; aORGENOTYPE (95% CI) values were 1.31 (1.09-1.58) (P = 0.005) and 1.18 (1.03-1.35) (P = 0.015), respectively; however, this was non-significant after Bonferroni correction.


CONCLUSIONS
This study validates the association between a functional polymorphism in the 5' UTR of ANKH and CC and shows for the first time that this is independent of age and OA - the two key risk factors for CC. It shows that other SNPs in ANKH may also associate with CC. This supports the role of extracellular inorganic pyrophosphate in the pathogenesis of CC. The findings of this hospital-based study require replication in a community-based population.
Abhishek
A
Abhishek
Sally
S
Doherty
Rose
R
Maciewicz
Kenneth
K
Muir
Weiya
W
Zhang
Michael
M
Doherty
Anna M
AM
Valdes
D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D002805:Chondrocalcinosis / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000150:complications; D028061:Phosphate Transport Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics
C498770:ANKH protein, human; D028061:Phosphate Transport Proteins