Canalis Ernesto, Sanjay Archana, Yu Jungeun, Zanotti Stefano
Departments of Orthopaedic Surgery, UConn Musculoskeletal Institute, UConn Health, Farmington, CT, USA.
Department of Medicine, UConn Musculoskeletal Institute, UConn Health, Farmington, CT, USA.
Endocrinology. 2017 Apr 1;158(4):730-742. doi: 10.1210/en.2016-1787.
Notch receptors play a central role in skeletal development and bone remodeling. Hajdu-Cheney syndrome (HCS), a disease characterized by osteoporosis and fractures, is associated with gain-of-NOTCH2 function mutations. To study HCS, we created a mouse model harboring a point 6955C>T mutation in the Notch2 locus upstream of the proline, glutamic acid, serine, and threonine domain, leading to a Q2319X change at the amino acid level. Notch2Q2319X heterozygous mutants exhibited cancellous and cortical bone osteopenia. Microcomputed tomography demonstrated that the cancellous and cortical osteopenic phenotype was reversed by the administration of antibodies generated against the negative regulatory region (NRR) of Notch2, previously shown to neutralize Notch2 activity. Bone histomorphometry revealed that anti-Notch2 NRR antibodies decreased the osteoclast number and eroded surface in cancellous bone of Notch2Q2319X mice. An increase in osteoclasts on the endocortical surface of Notch2Q2319X mice was not observed in the presence of anti-Notch2 NRR antibodies. The anti-Notch2 NRR antibody decreased the induction of Notch target genes and Tnfsf11 messenger RNA levels in bone extracts and osteoblasts from Notch2Q2319X mice. In vitro experiments demonstrated increased osteoclastogenesis in Notch2Q2319X mutants in response to macrophage colony-stimulating factor and receptor activator of nuclear factor-κB ligand, and these effects were suppressed by the anti-Notch2 NRR. In conclusion, Notch2Q2319X mice exhibit cancellous and cortical bone osteopenia that can be corrected by the administration of anti-Notch2 NRR antibodies.
Notch受体在骨骼发育和骨重塑中起着核心作用。Hajdu-Cheney综合征（HCS）是一种以骨质疏松和骨折为特征的疾病，与NOTCH2功能获得性突变有关。为了研究HCS，我们创建了一个小鼠模型，该模型在脯氨酸、谷氨酸、丝氨酸和苏氨酸结构域上游的Notch2基因座中存在一个6955C>T点突变，导致氨基酸水平上的Q2319X变化。Notch2Q2319X杂合突变体表现出松质骨和皮质骨骨质减少。微计算机断层扫描显示，通过给予针对Notch2负调控区域（NRR）产生的抗体，可以逆转松质骨和皮质骨骨质减少的表型，先前已证明该抗体可中和Notch2活性。骨组织形态计量学显示，抗Notch2 NRR抗体减少了Notch2Q2319X小鼠松质骨中的破骨细胞数量和侵蚀表面。在存在抗Notch2 NRR抗体的情况下，未观察到Notch2Q2319X小鼠内皮质表面的破骨细胞增加。抗Notch2 NRR抗体降低了Notch2Q2319X小鼠骨提取物和成骨细胞中Notch靶基因和Tnfsf11信使RNA水平的诱导。体外实验表明，Notch2Q2319X突变体对巨噬细胞集落刺激因子和核因子-κB受体激活剂配体的反应中破骨细胞生成增加，而这些作用被抗Notch2 NRR抑制。总之，Notch2Q2319X小鼠表现出松质骨和皮质骨骨质减少，通过给予抗Notch2 NRR抗体可以纠正这种情况。
