Multi-tissue epigenetic analysis of the osteoarthritis susceptibility locus mapping to the plectin genePLEC

Abstract

Running headline: Epigenetic analysis of the PLEC OA risk locusObjective 1 Osteoarthritis (OA) associated single nucleotide polymorphism (SNP) rs11780978 correlates 2 with differential expression of PLEC, and methylation quantitative trait loci (mQTLs) at PLEC 3 CpGs in cartilage. This implies that methylation links chondrocyte genotype and phenotype, 4 thus driving the functional effect. PLEC encodes plectin, a cytoskeletal protein that enables 5 tissues to respond to mechanical forces. We sought to assess whether PLEC functional effects 6 were cartilage specific. 7 8 Method 9Cartilage, fat pad, synovium and peripheral blood were collected from patients undergoing 10 arthroplasty. PLEC CpGs were analysed for mQTLs and allelic expression imbalance (AEI) 11 was performed. We focussed on previously reported mQTL clusters neighbouring cg19405177 12 and cg14598846. Plectin was knocked down in a mesenchymal stem cell (MSC) line using 13 CRISPR/Cas9 and cells phenotyped by RNA-sequencing. 14 15Results 16 Novel mQTLs were discovered in fat pad, synovium and peripheral blood at both clusters. The 17 genotype-methylation effect of rs11780978 was stronger in cg14598846 than in cg19405177 18 and stronger in joint tissues than in peripheral blood. We observed AEI in synovium in the 19 same direction as for cartilage. Knocking-down plectin impacted on pathways reported to have 20 a role in OA, including Wnt signalling, glycosaminoglycan biosynthesis and immune 21 regulation. 22 23 Conclusions 24Synovium is also a target of the rs11780978 OA association functionally operating on PLEC. 25In fat pad, mQTLs were identified but these did not correlate with PLEC expression, suggesting 26 the functional effect is not joint-wide. Our study highlights interplay between genetic risk, 27 DNA methylation and gene expression in OA, and reveals clear differences between tissues 28 from the same diseased joint. 29 30

Genetic and Epigenetic Fine‐Tuning of TGFB1 Expression Within the Human Osteoarthritic Joint

“…Interindividual variability in gene expression often necessitates sample sizes of hundreds of patients for the detection of significant genotypeexpression correlations (32,33). A complementary approach for eQTL analysis, which greatly increases sensitivity, involves measuring allelic imbalance between the expression of gene transcripts, and has been widely applied in investigations of OA risk loci (24,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46). We were unable to utilize this approach in our study due to the low MAF and the absence of a suitable TGFB1 transcript SNP.…”

Insights into the molecular landscape of osteoarthritis in human tissues

“…They found tissue-specific differences in the associations between rs11780978 and PLEC methylation (present in all tissues, but stronger in joint tissues), between rs11780978 and PLEC expression (present in synovium in cartilage, but not in fat pad), and between PLEC expression and methylation in synovium. This study suggests that rs11780978 targets PLEC also in synovium, but not in fat pad, which highlights the tissue-specificity of these functional mechanisms [48].…”

Injectable amnion hydrogel-mediated delivery of adipose-derived stem cells for osteoarthritis treatment

“…PLEC is a large cytoskeletal protein that regulates signaling from the extracellular environment to the cell nucleus (32). In cartilage, the OA-associated single-nucleotide polymorphism correlates with differential expression of PLEC and with differential methylation of PLEC CpG dinucleotides (33). Intact vimentin intermediate filament network contributes to the maintenance of the chondrocyte phenotype (34).…”