The association between ANKH promoter polymorphism and chondrocalcinosis is independent of age and osteoarthritis: results of a case–control study
© Abhishek et al.; licensee BioMed Central Ltd. 2014
Received: 21 September 2013
Accepted: 24 January 2014
Published: 27 January 2014
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.
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.
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.
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.
Chondrocalcinosis (CC) most commonly results from calcium pyrophosphate (CPP) crystal deposition (CPPD) . CPPD may present as acute CCP crystal arthritis, CPPD with osteoarthritis (OA), chronic CPP crystal inflammatory arthritis, or asymptomatic CC . Age, OA, diuretic use, and joint injury are recognized risk factors for CC [1, 2]. Additionally, metabolic diseases that elevate extracellular pyrophosphate (ePPi) levels (hyperparathyroidism, hypomagnesemia, and hypophosphatasia), hemochromatosis, and familial predisposition are uncommon risk factors [1, 2]. Though rare, familial predisposition is reported from several countries and different ethnic groups [3–9]. The pattern of inheritance is usually autosomal dominant. The main clinical phenotype is characterized by early onset (in the 20s or 30s) of acute CPP crystal arthritis with florid polyarticular CC and variable severity of accompanying structural arthritis/OA. However, a second phenotype with later onset in the sixth to seventh decades and oligo-articular CC that more closely resembles sporadic CPPD has also been reported . This latter familial form may be more common than is recognized, the late onset of disease expression and geographic dispersal of families tending to mask such predisposition. An association with benign childhood fits appears unique to one UK family with early-onset polyarticular CC, and the responsible gene—CC gene 2 (CCAL2) on chromosome 5p15—was first identified in this family . Other kindreds with CC due to mutations at this locus  have been reported, and the responsible gene was subsequently identified as the ankylosis human (ANKH) gene . The other reported locus in an American family with premature OA and associated CPPD (CCAL1) is on chromosome 8q , and a specific gene predisposing to CPPD at this site has not been identified.
Study design and participants
Demographics of study participants
n = 658
n = 4,283
Age in years, mean (SD)
Female gender, number (percentage)
Body mass index in kg/m2, mean (SD)
Knee or hip OA, number (percentage)
Cases and controls
Cases were participants with CC at any joint, whereas controls did not have CC at any joint x-rayed.
Single-nucleotide polymorphism selection
Association between all single-nucleotide polymorphisms and chondrocalcinosis in the Genetics of Osteoarthritis and Lifestyle study
Reason for selection (association with):
Minor allele frequency, %
-4bpG > A 5′ UTR
Rotator cuff tear and low intracellular PPi 
Parathyroid hormone level 
Parathyroid hormone level 
Increased TNAP activity 
Rotator cuff tear 
Iron overload 
Iron overload 
Iron overload 
Genotyping was carried out at AstraZeneca laboratories in Macclesfield, UK, by using the Taqman method and at Kbioscience Ltd (Hertfordshire, UK) by using the Kompetitive Allele Specific PCR (KASPar) chemistry. All 17 SNPs were genotyped in the GOAL study. All selected SNPs in any gene which contained at least one SNP that associated with CC with an uncorrected P ≤0.10 in the GOAL study were genotyped in the NOAC study participants.
Data about age (years), height (centimeters), and weight (kilograms) were collected at the study visit. Height and weight were used to calculate body mass index (BMI) (kg/m2). OA was defined as knee or hip OA clinically severe enough to warrant consideration of joint replacement surgery.
Mean and standard deviation (SD) and number (percentage) were used for descriptive purposes. Chi-square test and student t test were used to compare categorical and continuous variables. Cases with CC were compared with controls without CC. All SNPs were checked for Hardy-Weinberg equilibrium (HWE). Data from the GOAL and NOAC studies were pooled together for analyzing genetic risk. Genotype odds ratio (ORGENOTYPE)—the OR for association between increasing number of minor alleles of an SNP and CC—was calculated. Binary logistic regression was used to calculate aORGENOTYPE (95% confidence interval, or CI) adjusting for age (tertiles), gender, BMI (tertiles), and OA. Additionally, ORGENOTYPE was meta-analyzed with published studies by using fixed effects analysis given the lack of heterogeneity between studies. Meta-analyses were performed by using R V.2.13.1 . Other analyses were carried out by using SPSSv14. Statistical significance for genetic association was set at P ≤0.003 after application of Bonferroni correction for multiple tests. Linkage disequilibrium for the four ANKH SNPs studied was estimated from unphased genotype data by using the Haploview 4.2 version .
Results and discussion
The descriptive characteristics of study participants are presented in Table 1. Three thousand one hundred forty-one GOAL and 1,800 NOAC study participants were included. The mean age (SD), number of females (percentage), and mean BMI (SD) of the GOAL study and NOAC study participants were 66.6 (7.9) and 70.5 (9.2) years, 1,520 (48.4%) and 1,045 (58.1%) women, and 29.3 (5.3) and 29.5 (5.6) kg/m2, respectively. GOAL study participants were significantly younger (P <0.001), were less likely to be female (P <0.001), and had similar BMI (P = 0.22) compared with the NOAC study participants.
Linkage disequilibrium between the genotyped single-nucleotide polymorphisms in ankylosis human ( ANKH ) gene
-4bpG > A 5′ UTR
-4bpG > A 5′ UTR
-4bpG > A 5′ UTR
Association between chondrocalcinosis and single-nucleotide polymorphisms in the combined dataset
-4bpG > A 5′ UTR
Comparison with published studies
Two studies have reported on the association between CC and HFE SNPs [20, 21]. Of these, one study reported genotype data about rs1800562, and rs1799945 without reporting full data on compound heterozygote numbers , whereas the other did not report detailed genotype data . Therefore, the latter study was not included in the meta-analysis. In a meta-analysis of the data of the present study and of the study by Alizadeh et al. , the values for pooled ORGENOTYPE (95% CI) for association between rs1799945 and rs1800562 and CC were 1.20 (1.04-1.39) (P = 0.015) and 1.08 (0.88-1.33) (P = 0.445), respectively. Similarly, the results of the present study and the previous study that reported an association between CC and -4bpG > A transition in the 5′ UTR of ANKH were meta-analyzed . The pooled ORGENOTYPE (95% CI) was 1.36 (1.13-1.61) (P = 0.001).
The present study confirms the association between CC and -4bpG > A transition in the 5′ UTR of ANKH. It is the first study to show that this association is independent of age and OA, which are the two major established risk factors of CC. This study also raises the possibility that other SNPs in ANKH (for example, rs3045) may also associate with CC. However, in keeping with previous reports, there was no association between SNPs in TNAP or ENPP1 and CC .
ANKH encodes a multipass transmembrane protein (ANKH) in joints and other tissues and participates in the export of intracellular PPi [30, 31]. PPi cannot diffuse across cell membranes passively, and ANKH is the principal way in which intracellular PPi reaches the extracellular environment. ANKH-mediated control of PPi levels regulates tissue calcification and susceptibility to arthritis [30, 31]. The autosomal dominant mutations in ANKH are thought to confer a gain in PPi transport function leading to increased extracellular PPi levels [14, 32]. Functional assays show that the -4bpG > A transition in the 5′ UTR of ANKH reduces intracellular PPi (a surrogate for increased transcellular PPi export) and increases ANKH expression in vitro[14, 18]. The minor alleles of rs3045 also result in lower intracellular PPi levels in vitro, providing external validity to our finding of a possible association between this polymorphism and CC . These two SNPs are not in linkage disequilibrium. The minor allele frequency for the -4bpG > A transition in 5′ UTR of ANKH and rs3045 is higher in this study than that in the multi-ethnic 1000 Genomes Project. (See Additional file 2: Table S2 for genotype frequencies of the selected SNPs in the 1000 Genomes Project). This may explain, in part, why CPPD is more common in Caucasians than in other ethnicities.
Though not statistically significant, results from the data suggest that rs1799945 (HFE SNP associated with smaller iron overload), but not rs1800562 (HFE SNP associated with greater iron overload), may associate with CC. Similar findings have been reported previously . The lack of association between homozygosity for minor allele at rs1800562 and CC may be due to a channeling bias (that is, patients with hemochromatosis are excluded from these studies).
This is the largest reported study of genetic risk factors for CC. This study has several strengths. First, the analysis of genetic risk was adjusted for factors that associate with CC, specifically age and OA, and also for gender, which associates with iron overload. Moreover, correction for multiple testing was applied to reduce the chances of a type I error. However, this study has several caveats. First, this is a hospital-based study carried out by reconstituting cases and controls within cohorts assembled primarily to examine risk factors for knee or hip OA within the East Midlands region of the UK. Cases with mild to moderate large-joint OA were not included. The study sample therefore does not resemble a community-based population and is restricted to one area of the country. Moreover, as more than 78% of participants had severe large-joint OA, the results may be confounded by their OA status. However, to minimize any confounding and to improve the generalizability of these findings, we have adjusted for OA at the knee and hip. Second, participants of the NOAC study did not have the same extensive radiographic phenotyping of CC as participants of the GOAL study. As a result, some NOAC study participants who may have CC at distant joints without CC at the joint to be replaced will be misclassified as ‘CC negative’ controls. This misclassification is likely to minimize the genetic association and does not invalidate the genetic associations observed in this study.
This study validates an established genetic association with CC and shows that this is independent of age and OA. This study also raises the possibility that other SNPs in ANKH associate with CC. Larger studies with greater power are required to confirm these findings. Finally, the findings of this study derived from a hospital-based cohort warrant confirmation in a community-based population including cases with mild to moderate disease and in other countries.
AMV and MD are joint senior authors.
- 5′ UTR:
5′ untranslated region
body mass index
- CCAL (1 or 2):
chondrocalcinosis (1 or 2) gene
calcium pyrophosphate crystal
calcium pyrophosphate crystal deposition
ectonucleotide pyrophosphatase 1
Genetics of Osteoarthritis and Lifestyle
Nottingham Osteoarthritis Case-Control
genotype odds ratio
tissue non-specific alkaline phosphatase.
AstraZeneca UK funded the GOAL study sample and data collection. The Arthritis Research Council provided infrastructure support during the GOAL study (grant 14581) and for part of the NOAC study. Genotyping for the NOAC study was funded by the EU FP7 large collaborative project grant 200800 TREAT-OA.
- Zhang W, Doherty M, Bardin T, Barskova V, Guerne PA, Jansen TL, Leeb BF, Perez-Ruiz F, Pimentao J, Punzi L: European league against rheumatism recommendations for calcium pyrophosphate deposition. Part I: terminology and diagnosis. Ann Rheum Dis. 2011, 70: 563-570. 10.1136/ard.2010.139105.View ArticlePubMedGoogle Scholar
- Richette P, Bardin T, Doherty M: An update on the epidemiology of calcium pyrophosphate dihydrate crystal deposition disease. Rheumatology (Oxford). 2009, 48: 711-715. 10.1093/rheumatology/kep081.View ArticleGoogle Scholar
- Abhishek A, Doherty M: Pathophysiology of articular chondrocalcinosis–role of ANKH. Nat Rev Rheumatol. 2011, 7: 96-104. 10.1038/nrrheum.2010.182.View ArticlePubMedGoogle Scholar
- Andrew LJ, Brancolini V, de la Pena LS, Devoto M, Caeiro F, Marchegiani R, Reginato A, Gaucher A, Netter P, Gillet P, Loeuille D, Prockop DJ, Carr A, Wordsworth BF, Lathrop M, Butcher S, Considine E, Everts K, Nicod A, Walsh S, Williams CJ: Refinement of the chromosome 5p locus for familial calcium pyrophosphate dihydrate deposition disease. Am J Hum Genet. 1999, 64: 136-145. 10.1086/302186.View ArticlePubMedPubMed CentralGoogle Scholar
- Béjia I, Rtibi I, Touzi M, Zrour S, Younes M, Naceur B: Familial calcium pyrophosphate dihydrate deposition disease. A Tunisian kindred. Joint Bone Spine. 2004, 71: 401-408. 10.1016/j.jbspin.2003.10.012.View ArticlePubMedGoogle Scholar
- Gaudreau A, Camerlain M, Pibarot ML, Beauregard G, Lebrun A, Petitclerc C: Familial articular chondrocalcinosis in Quebec. Arthritis Rheum. 1981, 24: 611-615. 10.1002/art.1780240407.View ArticlePubMedGoogle Scholar
- Hamza M, Meddeb N, Bardin T: Hereditary chondrocalcinosis in a Tunisian family. Clin Exp Rheumatol. 1992, 10: 43-49.PubMedGoogle Scholar
- Hamza M, Ayed K, Bardi R, Gebuhrer L, Betuel H, Bardin T, Plaetke R, Lathrop M: HLA-antigens in a Tunisian familial chondrocalcinosis. Dis Markers. 1990, 8: 109-112.PubMedGoogle Scholar
- Reginato AJ, Hollander JL, Martinez V, Valenzuela F, Schiapachasse V, Covarrubias E, Jacobelli S, Arinoviche R, Silcox D, Ruiz F: Familial chondrocalcinosis in the Chiloe Islands, Chile. Ann Rheum Dis. 1975, 34: 260-268. 10.1136/ard.34.3.260.View ArticlePubMedPubMed CentralGoogle Scholar
- Riestra JL, Sanchez A, Rodriguez-Valverde V, Alonso JL, de la Hera M, Merino J: Radiographic features of hereditary articular chondrocalcinosis. A comparative study with the sporadic type. Clin Exp Rheumatol. 1988, 6: 369-372.PubMedGoogle Scholar
- Doherty M, Hamilton E, Henderson J, Misra H, Dixey J: Familial chondrocalcinosis due to calcium pyrophosphate dihydrate crystal deposition in English families. Br J Rheumatol. 1991, 30: 10-15. 10.1093/rheumatology/30.1.10.View ArticlePubMedGoogle Scholar
- Williams CJ, Zhang Y, Timms A, Bonavita G, Caeiro F, Broxholme J, Cuthbertson J, Jones Y, Marchegiani R, Reginato A, Russell RG, Wordsworth BP, Carr AJ, Brown MA: Autosomal dominant familial calcium pyrophosphate dihydrate deposition disease is caused by mutation in the transmembrane protein ANKH. Am J Hum Genet. 2002, 71: 985-991. 10.1086/343053.View ArticlePubMedPubMed CentralGoogle Scholar
- Baldwin CT, Farrer LA, Adair R, Dharmavaram R, Jimenez S, Anderson L: Linkage of early-onset osteoarthritis and chondrocalcinosis to human chromosome 8q. Am J Hum Genet. 1995, 56: 692-697.PubMedPubMed CentralGoogle Scholar
- Zhang Y, Johnson K, Russell RG, Wordsworth BP, Carr AJ, Terkeltaub RA, Brown MA: Association of sporadic chondrocalcinosis with a -4-basepair G-to-A transition in the 5’-untranslated region of ANKH that promotes enhanced expression of ANKH protein and excess generation of extracellular inorganic pyrophosphate. Arthritis Rheum. 2005, 52: 1110-1117. 10.1002/art.20978.View ArticlePubMedGoogle Scholar
- Zhang W, Neame R, Doherty S, Doherty M: Relative risk of knee chondrocalcinosis in siblings of index cases with pyrophosphate arthropathy. Ann Rheum Dis. 2004, 63: 969-973. 10.1136/ard.2003.015206.View ArticlePubMedPubMed CentralGoogle Scholar
- Valdes AM, De Wilde G, Doherty SA, Lories RJ, Vaughn FL, Laslett LL, Maciewicz RA, Soni A, Hart DJ, Zhang W: The Ile585Val TRPV1 variant is involved in risk of painful knee osteoarthritis. Ann Rheum Dis. 2011, 70: 1556-1561. 10.1136/ard.2010.148122.View ArticlePubMedPubMed CentralGoogle Scholar
- Robertson J, Zhang W, Liu JJ, Muir KR, Maciewicz RA, Doherty M: Radiographic assessment of the index to ring finger ratio (2D:4D) in adults. J Anat. 2008, 212: 42-48.PubMedPubMed CentralGoogle Scholar
- Peach CA, Zhang Y, Dunford JE, Brown MA, Carr AJ: Cuff tear arthropathy: evidence of functional variation in pyrophosphate metabolism genes. Clin Orthop Relat Res. 2007, 462: 67-72.View ArticlePubMedGoogle Scholar
- Vistoropsky Y, Keter M, Malkin I, Trofimov S, Kobyliansky E, Livshits G: Contribution of the putative genetic factors and ANKH gene polymorphisms to variation of circulating calciotropic molecules, PTH and BGP. Hum Mol Genet. 2007, 16: 1233-1240. 10.1093/hmg/ddm071.View ArticlePubMedGoogle Scholar
- Alizadeh BZ, Njajou OT, Hazes JM, Hofman A, Slagboom PE, Pols HA, van Duijn CM: The H63D variant in the HFE gene predisposes to arthralgia, chondrocalcinosis and osteoarthritis. Ann Rheum Dis. 2007, 66: 1436-1442. 10.1136/ard.2006.063099.View ArticlePubMedPubMed CentralGoogle Scholar
- Timms AE, Sathananthan R, Bradbury L, Athanasou NA, Wordsworth BP, Brown MA: Genetic testing for haemochromatosis in patients with chondrocalcinosis. Ann Rheum Dis. 2002, 61: 745-747. 10.1136/ard.61.8.745.View ArticlePubMedPubMed CentralGoogle Scholar
- Goseki-Sone M, Sogabe N, Fukushi-Irie M, Mizoi L, Orimo H, Suzuki T, Nakamura H, Orimo H, Hosoi T: Functional analysis of the single nucleotide polymorphism (787T>C) in the tissue-nonspecific alkaline phosphatase gene associated with BMD. J Bone Miner Res. 2005, 20: 773-782.View ArticlePubMedGoogle Scholar
- Suk EK, Malkin I, Dahm S, Kalichman L, Ruf N, Kobyliansky E, Toliat M, Rutsch F, Nürnberg P, Livshits G: Association of ENPP1 gene polymorphisms with hand osteoarthritis in a Chuvasha population. Arthritis Res Ther. 2005, 7: R1082-R1090. 10.1186/ar1786.View ArticlePubMedPubMed CentralGoogle Scholar
- Valli-Jaakola K, Suviolahti E, Schalin-Jäntti C, Ripatti S, Silander K, Oksanen L, Salomaa V, Peltonen L, Kontula K: Further evidence for the role of ENPP1 in obesity: association with morbid obesity in Finns. Obesity (Silver Spring). 2008, 16: 2113-2119. 10.1038/oby.2008.313.View ArticleGoogle Scholar
- Benyamin B, McRae AF, Zhu G, Gordon S, Henders AK, Palotie A, Peltonen L, Martin NG, Montgomery GW, Whitfield JB, Visscher PM: Variants in TF and HFE explain approximately 40% of genetic variation in serum-transferrin levels. Am J Hum Genet. 2009, 84: 60-65. 10.1016/j.ajhg.2008.11.011.View ArticlePubMedPubMed CentralGoogle Scholar
- R Development Core Team: R: A Language and Environment for Statistical Computing. 2010, Vienna, Austria: R Foundation for Statistical Computing, Retrieved from http://www.R-project.orgGoogle Scholar
- Barrett JC, Fry B, Maller J, Daly MJ: Haploview: analysis and visualization of LD and haplotype maps. Bioinformatics. 2005, 21: 263-265. 10.1093/bioinformatics/bth457.View ArticlePubMedGoogle Scholar
- Fauvert D, Brun-Heath I, Lia-Baldini AS, Bellazi L, Taillandier A, Serre JL, de Mazancourt P, Mornet E: Mild forms of hypophosphatasia mostly result from dominant negative effect of severe alleles or from compound heterozygosity for severe and moderate alleles. BMC Med Genet. 2009, 10: 51.View ArticlePubMedPubMed CentralGoogle Scholar
- Zhang Y, Brown MA, Peach C, Russell G, Wordsworth BP: Investigation of the role of ENPP1 and TNAP genes in chondrocalcinosis. Rheumatology (Oxford). 2007, 46: 586-589.View ArticleGoogle Scholar
- Ho AM, Johnson MD, Kingsley DM: Role of the mouse ank gene in control of tissue calcification and arthritis. Science. 2000, 289: 265-270. 10.1126/science.289.5477.265.View ArticlePubMedGoogle Scholar
- Gurley KA, Reimer RJ, Kingsley DM: Biochemical and genetic analysis of ANK in arthritis and bone disease. Am J Hum Genet. 2006, 79: 1017-1029. 10.1086/509881.View ArticlePubMedPubMed CentralGoogle Scholar
- Pendleton A, Johnson MD, Hughes A, Gurley KA, Ho AM, Doherty M, Dixey J, Gillet P, Loeuille D, McGrath R, Reginato A, Shiang R, Wright G, Netter P, Williams C, Kingsley DM: Mutations in ANKH cause chondrocalcinosis. Am J Hum Genet. 2002, 71: 933-940. 10.1086/343054.View ArticlePubMedPubMed CentralGoogle Scholar
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