Functional analysis of the osteoarthritis susceptibility–associated GDF5 regulatory polymorphism

Abstract

Objective. Single-nucleotide polymorphism (SNP) rs143383 (T to C) in the 5 -untranslated region (5 -UTR) of GDF5 has recently been reported to be associated with osteoarthritis (OA) susceptibility, with lower expression of the risk-associated T allele observed in vitro and in vivo. The in vivo studies were performed on cartilage tissue from OA patients. The present study was undertaken to expand the analysis of the effect of this SNP on GDF5 allelic expression to more joint tissue types, to investigate for cis and trans factors that interact with the SNP, and to examine novel cis-acting GDF5 regulatory polymorphisms.Methods. Tissue samples were collected from OA patients undergoing joint replacement of the hip or knee. Nucleic acid was extracted, and, using rs143383 and an assay that discriminates and quantifies allelic expression, the relative amount of GDF5 expression from the T and C alleles was measured. Additional common variants in the GDF5 transcript sequence were interrogated as potential regulatory elements using allelic expression and luciferase reporter assays, and electrophoretic mobility shift assays were used to search for trans factors binding to rs143383.Results. We observed a consistent allelic expression imbalance of GDF5 in all tissues tested, implying that the functional effect mediated by rs143383 on GDF5 expression is joint-wide. We identified a second polymorphism, located in the 3 -UTR of GDF5, that influenced allelic expression of the gene independent of rs143383. Finally, we observed differential binding of deformed epidermal autoregulatory factor 1 (DEAF-1) to the 2 alleles of rs143383.Conclusion. These findings show that the OA susceptibility mediated by polymorphism in GDF5 is not restricted to cartilage, emphasizing the need to consider the disease as involving the whole joint. The existence of an additional cis-acting regulatory polymorphism highlights the complexity of the regulation of expression of this important OA susceptibility locus. DEAF-1 is a trans-acting factor that merits further investigation as a potential tool for modulating GDF5 expression.

Analysis of association between IL-1β, CASP-9, and GDF5 variants and low-back pain in Chinese male soldiers

“…Previous studies have found that a function of SNP in GDF5 is associated with susceptibility to osteoarthritis at different joint locations and to lumbar disc degeneration. 6,16,24 In the present study, the T allele as a predisposing allele was more common in the case group individuals than in the control group individuals. The polymorphism of GDF5 may have an impact on the development of bone, cartilage, and soft tissue in the low-back area through exerting allelic differences on transcriptional activity.…”

Transcriptional Regulation of Articular Chondrocyte Function and Its Implication in Osteoarthritis

“…This association was confirmed in a large-scale meta-analysis; however, the magnitude of effect was less than previously reported (Evangelou et al, 2009). Interestingly, Egli et al found that GDF5 expression imbalance was not limited to articular cartilage, but found in multiple joint tissues analyzed (synovium, fat pad, meniscus, ligaments) (Egli et al, 2009). …”

Recent advances in association studies of osteoarthritis susceptibility genes

“…28 The most associated SNP (rs143383) is a functional variant, and the susceptibility allele shows decreased GDF5 transcription in vitro and in vivo. [28][29][30] The same allele was reported to be associated with adult height in Caucasians through a GWAS using subjects with non-insulin-dependent diabetes mellitus. 31 Valdes et al 32 assessed rs143383 for OA in the UK Caucasians using 999 knee OA, 843 hip OA and 1166 control samples, and they replicated the association of GDF5 in knee OA (OR¼1.29, 95% CI of 1.14-1.47; P¼8Â10 À5 ).…”