title: Identification and analysis of a SMAD3 cis-acting eQTL operating in primary osteoarthritis and in the aneurysms and osteoarthritis syndrome.
abstract: OBJECTIVE
  The TGF-β pathway plays a central role in joint development with polymorphism in TGF-β pathway genes implicated in osteoarthritis susceptibility. One association is to rs12901499, within intron 1 of SMAD3. Since rs12901499 is not in linkage disequilibrium with a non-synonymous polymorphism, it is likely the association is operating by influencing expression of SMAD3.
  
  
  METHODS
  Using tissues from the joints of primary osteoarthritis patients who had undergone joint replacement we measured the overall expression of SMAD3 by quantitative real-time PCR. We also measured allelic expression of SMAD3 using these tissues and vascular smooth muscle cells from patients with aneurysms and osteoarthritis syndrome, a rare condition featuring early-onset osteoarthritis. We tested the functional effect of SNPs in vitro using luciferase assays and assessed association with osteoarthritis using a large osteoarthritis case-control dataset.
  
  
  RESULTS
  We observed that genotype at rs12901499 did not correlate with overall SMAD3 expression or allelic expression. However, genotype at a 3'UTR SNP, rs8031440, did correlate with SMAD3 expression in cartilage (P = 0.005) which was supported by allelic expression data showing that the G allele correlated with decreased SMAD3 expression in joint tissues and vascular smooth muscle cells. This G allele was underrepresented in osteoarthritis cases vs controls (P = 0.027, odds ratio = 0.921). rs8031440 is in perfect linkage disequilibrium with five other SMAD3 3'UTR SNPs and our luciferase analysis identified rs3743342 and rs12595334 as being functional.
  
  
  CONCLUSIONS
  SMAD3 is subject to cis-acting regulatory polymorphism in the tissues of relevance to both primary osteoarthritis and the aneurysms-osteoarthritis syndrome.
authors.affiliation: Newcastle University, Institute of Cellular Medicine, Newcastle upon Tyne, UK. Electronic address: e.v.a.raine@ncl.ac.uk.
authors.forename: E V A
authors.initials: EV
authors.lastname: Raine
authors.affiliation: Newcastle University, Institute of Cellular Medicine, Newcastle upon Tyne, UK.
authors.forename: L N
authors.initials: LN
authors.lastname: Reynard
authors.affiliation: Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: I M B H
authors.initials: IM
authors.lastname: van de Laar
authors.affiliation: Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: A M
authors.initials: AM
authors.lastname: Bertoli-Avella
authors.affiliation: Newcastle University, Institute of Cellular Medicine, Newcastle upon Tyne, UK. Electronic address: john.loughlin@ncl.ac.uk.
authors.forename: J
authors.initials: J
authors.lastname: Loughlin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D000783:Aneurysm / Q000235:genetics*; D002358:Cartilage, Articular / Q000378:metabolism; D016022:Case-Control Studies; D002478:Cells, Cultured; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D015207:Osteoarthritis, Hip / Q000235:genetics* / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000235:genetics* / Q000378:metabolism; D040641:Quantitative Trait Loci / Q000235:genetics*; D051900:Smad3 Protein / Q000235:genetics* / Q000378:metabolism; D013577:Syndrome
chemical_list: C497790:SMAD3 protein, human; D051900:Smad3 Protein
keywords: Allelic expression; Aneurysm; Genetics; Osteoarthritis; SMAD3; Susceptibility