Figure 4.

Distribution of Gly → Xaa mutations within the collagen type I triple-helical region causing OI. Residues replacing Gly within the Gly-Xaa-Yaa triplets are indicated (●, Ala; ♦, Arg; *, Asp; ○, Cys; □, Glu; ▴, Ser; ▵, Val) and classified as mild, moderate, or severe. Mutations are those collected in the collagen mutation database (www.le.ac.uk/genetics/collagen/; ref. 10), and further unpublished ones are included with permission of the group of A. De Paepe (personal communication). Dotted lines indicate positions for which different mutations are known where the severity of the disease depends on the identity of the encoded amino acid residue.