Cindy Boer

Hand osteoarthritis and Matrix-Gla Protein | 123 3.1 ▲ Figure 2: Locus zoom plot for rs4764133. 150kb upstream and downstream of rs4764133 has been taken as plotted region (A). Zoom in on MGP and three SNPs in high LD with top SNP that are located in the MGP mRNA transcript (B). Also represented is ROADMAP chromatin 18-state data of two tissue types: human mesenchymal stem cell (hMSC)-derived cultured chondrogenic cells and primary osteo- blasts. In both these cell types, the chromatin contains active marks surrounding the MGP promoter. LD:linkage disequilibrium; MGP: matrix Gla protein. in articular cartilage ( Supplementary Figure 2a ). Nonetheless, neither MGP , ERP27 , ART4,SMOC3 nor C12orf60 showed significant difference in gene expression between paired Preserved (P) and OA lesioned (OAL) articular cartilage. However, while these genes are not differentially expressed in OA affected cartilage, it is possible that the identified GWAS SNPs affect gene transcription. When we analysed the relationship be- tween the top SNP and expression analysis in a classical expression quantitative trait loci (eQTL) analysis, we did not to detect significant correlations between rs1049897, rs4236 or rs1800801 and absolute MGP , ERP27 , ART4 , SMOC3 or C12orf60 expression levels ( Supplementary Figure 2b ). However, we did observe several variants in high LD located in the mRNA transcript of MGP and C12orf60 , allowing us to assess allele spe- cific expression (ASE) for these genes. We were unable to study ASE for ART4 , SMOC3