Changes in expression of BMP family members were variable, of note BMP4 (P < 0.001) and BMP2 (P < 0.001) were upregulated in OI compared with controls and the BMP inhibitors NOG (P < 0.001), CHRD (P < 0.001), MSTN (P < 0.001) and TGFA (P < 0.001) were downregulated (Fig. 1E and F). The gene discussed is CHRD; the disease is osteogenesis imperfecta.