- Genomewide linkage and linkage disequilibrium analyses identify COL6A1, on chromosome 21, as the locus for ossification of the posterior longitudinal ligament of the spine. Tanaka, T., Ikari, K., Furushima, K., Okada, A., Tanaka, H., Furukawa, K., Yoshida, K., Ikeda, T., Ikegawa, S., Hunt, S.C., Takeda, J., Toh, S., Harata, S., Nakajima, T., Inoue, I. Am. J. Hum. Genet. (2003)