ENPP1 and ossification of the posterior longitudinal ligament of the spine: After the identification of ENPP1 as the causative gene in ttw mice with a severe OPLL phenotype, the same investigators searched for pathogenic ENPP1 variants in 323 Japanese patients with OPLL, identifying 10 candidates (NC_000006.12:g.131808012G > A [rs1800949], NC_000006.12:g.131807739_131807740delAA [rs1799773], NC_000006.12:g.131808012G > A [rs1800948], c.179 T > C [rs1781304340], c.517A > C [rs1044498], c.802 T > C [rs17847050], c.860C > T [rs190947144], c.915 + 27 T > G [rs9493113], c.2101-11delT [rs397832689], c.2335A > C [rs1805138]) (Fig. 1) [83].