Identification and analysis of a SMAD3 cis -acting eQTL operating in primary osteoarthritis and in the aneurysms and osteoarthritis syndrome

• Published in: Osteoarthritis and cartilage Vol. 22; no. 5; pp. 698 - 705
• Main Authors: Raine, E.V.A, Reynard, L.N, van de Laar, I.M.B.H, Bertoli-Avella, A.M, Loughlin, J
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.05.2014; W.B. Saunders For The Osteoarthritis Research Society
• Subjects: Aged; Aged, 80 and over; Alleles; Allelic expression; Aneurysm; Aneurysm - genetics; Cartilage, Articular - metabolism; Case-Control Studies; Cells, Cultured; Female; Genetic Predisposition to Disease; Genetics; Genotype; Haplotypes; Humans; Male; Middle Aged; Muscle, Smooth, Vascular - metabolism; Osteoarthritis; Osteoarthritis, Hip - genetics; Osteoarthritis, Hip - metabolism; Osteoarthritis, Knee - genetics; Osteoarthritis, Knee - metabolism; Quantitative Trait Loci - genetics; Rheumatology; SMAD3; Smad3 Protein - genetics; Smad3 Protein - metabolism; Susceptibility; Syndrome; Genetics; SMAD3; Allelic expression; Susceptibility; Osteoarthritis; Aneurysm
• ISSN: 1063-4584; 1522-9653
• DOI: 10.1016/j.joca.2014.02.931

Summary 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. Design 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. Conclusion SMAD3 is subject to cis -acting regulatory polymorphism in the tissues of relevance to both primary osteoarthritis and the aneurysms-osteoarthritis syndrome.