A previous study reported a similar phenotype for Csf1-/- osteopetrosis mice and suggested that the decreased PDGFB resulted from the impaired osteoclastogenesis in the cortical bone might be the cause of thin cortical bone.29 Here we detected the expression of PDGFB in the cortical bone and found a decrease in OsxCre;R26dn/dn mice compared to its control littermates (Fig. 4l), which indicated that there might be a further inhibition of osteogenesis in the cortical bone caused by the impaired osteoclastogenesis in OsxCre;R26dn/dn mice. The gene discussed is PDGFB; the disease is osteopetrosis.