Genetic analysis of cDNA isolated from these cells revealed no significant differences in expression of COL1A1, COL1A2 (Fig. 4A) or members of the angiotensin signalling pathway (Fig. 4B), and limited changes in members of the TGFβ signalling pathway (Fig. 4C) or genes known to be altered downstream of TGFβ (Fig. 4D) (data from OI fibroblasts shown in Fig. 5 and supplementary Fig. 3a; data from healthy controls, not shown). Here, COL1A1 is linked to osteogenesis imperfecta.