Notch signaling critically controls cell fate decisions in mammals, both during embryogenesis and in adults. In the skeleton, Notch suppresses osteoblast differentiation and sustains bone marrow mesenchymal progenitors during postnatal life. Stabilizing mutations of Notch2 cause the Hajdu-Cheney syndrome characterized by early onset osteoporosis in humans, but the mechanism whereby Notch inhibits bone accretion is not fully understood. Here we report that activation of Notch signaling by either Jagged1 or Notch2 intracellular domain suppresses glucose metabolism and osteoblast differentiation in primary cultures of bone marrow mesenchymal progenitors. Importantly, deletion of Notch2 in the limb mesenchyme increases both glycolysis and bone formation in the long bones of postnatal mice, whereas pharmacological reduction of glycolysis abrogates the excessive bone formation. Mechanistically, Notch reduces the expression of glycolytic and mitochondrial Complex I genes, resulting in a decease in mitochondrial respiration, superoxide production and Ampk activity. Forced activation of Ampk restores glycolysis in the face of Notch signaling. Thus, suppression of glucose metabolism contributes to the mechanism whereby Notch restricts osteoblastogenesis from bone marrow mesenchymal progenitors.
Seung-Yon Lee, Fanxin Long