Genetic loci that regulate ectopic calcification in response to knee trauma in LG/J by SM/J advanced intercross mice

Abstract

This study reports on genetic susceptibility to ectopic calcification in the LG/J and SM/J advanced intercross mice. Using 347 mice in 98 full-sibships, destabilization of medial meniscus (DMM) was performed to induce joint injury. We performed quantitative trait locus (QTL) analysis to map ectopic calcification phenotypes to discrete genomic locations. To validate the functional significance of the selected QTL candidate genes, we compared mRNA expression between parental LG/J and SM/J inbred strains. We found that joint destabilization instigated ectopic calcifications as detected and quantified by micro-CT. Overall, we detected 20 QTLs affecting synovial and meniscus calcification phenotypes with 11 QTLs linked to synovial calcification. Functional and bioinformatic analyses of single nucleotide polymorphism identified functional classifications relevant to angiogenesis (Myo1e, Kif26b, Nprl3, Stab2, Fam105b), bone metabolism/calcification (Tle3, Tgfb2, Lipc, Nfe2l1, Ank, Fam105b), arthritis (Stab2, Tbx21, Map4k4, Hoxb9, Larp6, Col1a2, Adam10, Timp3, Nfe2l1, Trpm3), and ankylosing-spondylitis (Ank, Pon1, Il1r2, Tbkbp1) indicating that ectopic calcification involves multiple mechanisms. Furthermore, the expression of 11 candidate genes was significantly different between LG/J and SM/J. Correlation analysis showed that Aff3, Fam81a, Syn3, and Ank were correlated with synovial calcification. Taken together, our findings of multiple genetic loci suggest the involvement of multiple genes contributing to ectopic calcification.

Evidence for Genetic Contribution to Variation in Posttraumatic Osteoarthritis in Mice

“…In order to examine strain‐specific gene expression in response to DMM surgery, we used material from the histology slides to probe a panel of 78 candidate genes compiled previously for our work on ectopic calcifications and cartilage repair . The list of candidate genes is in Supplementary Table 2, http://onlinelibrary.wiley.com/doi/10.1002/art.40730/abstract.…”

“…We have recently shown that mice develop ectopic calcifications (i.e., calcified nodules in and around the synovium) after surgical DMM or mechanical loading . In the present study, we quantified these nodules after joints were scanned by micro‐CT scanner as described previously .…”

Post-Traumatic Osteoarthritis in Mice Following Mechanical Injury to the Synovial Joint

“…Although we have shown that synovitis and cartilage degeneration are uncoupled23, others have suggested their co-occurrence53. We have recently shown that ectopic calcification has a strong genetic component to it as evidenced by identification of quantitative trait loci in the advanced intercross population of LG/J and SM/J54. Using LG/J, SM/J and their advanced intercross, we previously discovered that joint destabilization instigates meniscal and synovial ectopic calcification54.…”

“…We have recently shown that ectopic calcification has a strong genetic component to it as evidenced by identification of quantitative trait loci in the advanced intercross population of LG/J and SM/J54. Using LG/J, SM/J and their advanced intercross, we previously discovered that joint destabilization instigates meniscal and synovial ectopic calcification54. Interestingly, we observed the same phenotype in loaded knees and more so in the knees with ACL tear (data not shown), thus strengthening our hypothesis, that calcification occurs in unstable joints.…”

Enhanced cartilage repair in ‘healer’ mice—New leads in the search for better clinical options for cartilage repair

“…For heritability studies, the use of inbred strains is preferred because any phenotypic variation detected is due to different combinations of each parental genome without the confounding influence of different genetic backgrounds that outbred strains would have [59]. These LG/J and SM/J inbred strains have been studied for a range of complex musculoskeletal phenotypes including ectopic calcification [60], long bone growth, mechanical properties [61] and muscle weight [62]. …”