BMP4 and ossification of the posterior longitudinal ligament of the spine: In addition, Lin’s group has characterized a total of 18 BMP4 SNPs from 450 OPLL patients and 550 matched controls, and found that rs17563(C/T), rs76335800(A/T) and SNP8 (C>T) are the SNPs associated with increased genetic susceptibility to OPLL [56].