GJA1 and ossification of the posterior longitudinal ligament of the spine: In OPLL, mechanical stress-induced downregulation of vimentin in fibroblasts triggers ossification in the posterior longitudinal ligament (Zhang et al., 2014), whereas Connexin43 (Cx43), a gap junction protein, enhances fibroblast responses to mechanical strain, upregulates osteogenic gene expression and promotes ligament calcification (Yang et al., 2011).