Some, like osteogenesis imperfecta (OI), are primarily caused by mutations in structural proteins of the extracellular matrix, type I collagen in this case [320], whereas others are caused by mutations in components of the major signaling pathways, such as in the FGFR3, which causes achondroplasia (ACH) [321]. This evidence concerns the gene FGFR3 and achondroplasia.