Molecular Regulatory Mechanism of Calvaria Bone Development and Homeostasis

人类连锁研究表明，基因突变与胆固醇代谢和高孕产妇 胆固醇饮食导致颅面骨畸形，这表明胆固醇代谢异常可能 是颅面发育缺陷中广泛保守的机制。然而，它在很大程度上仍然是未知的 胆固醇代谢的改变如何导致颅面骨骼异常因此，这一目标 应用是为了确定胆固醇代谢异常，通过破坏Dhcr 7基因， （它编码一种参与胆固醇合成最后一步的酶，是胆固醇合成的致病基因。 Smith-Lemli-Opitz综合征）或Insig 1和Insig 2基因（为内质网 调节脂质生物合成的网状蛋白），引起成骨细胞（OB）分化异常， 测试颅面骨形成过程中下游靶分子的功能意义。很长的- 本项目的长期目标是深入了解颅面骨形成的机制， 用于骨骼疾病的药物和诊断工具。我们将使用鼠标来测试我们的工作假设。 遗传学和细胞生物学方法。在我们的初步研究中，我们发现：1）受损的胆固醇 合成导致加速骨形成; 2）过量的胆固醇合成导致骨减少 形成; 3）初级纤毛的形成，这在感受细胞信号中起着至关重要的作用， Dhcr 7敲除（KO）和神经嵴特异性Insig 1/2条件性敲除（cKO）小鼠; 4）WNT信号传导被阻断。 在Dhcr 7 KO和Insig 1/2 cKO小鼠中改变;和5）恢复胆固醇代谢畸变的正常化 Dhcr 7 KO和Insig 1/2 cKO小鼠的颅面骨缺损。我们的假设是正常胆固醇 代谢对正常颅面骨形成至关重要，将在以下具体目标中进行测试：1） 确定胆固醇代谢在颅面骨发育中的作用; 2）确定 骨中初级纤毛形成中的胆固醇代谢。这项研究将揭示一种新的骨形成机制， 发展和稳态，并将导致创新的诊断方法，治疗和预防 头骨畸形

Human linkage studies have shown that genetic mutations related to cholesterol metabolism and high maternal cholesterol diets result in craniofacial bone deformities, suggesting that cholesterol metabolic aberrations may be a widely conserved mechanism in craniofacial developmental defects. However, it is still largely unknown how altered cholesterol metabolism causes craniofacial bone abnormalities. Therefore, the objective of this application is to define how cholesterol metabolic aberrations, through disruption of either the Dhcr7 gene (which encodes an enzyme involved in the last step of cholesterol synthesis and is the causative gene for Smith-Lemli-Opitz syndrome) or the Insig1 and Insig2 genes (which provide instructions for endoplasmic reticulum proteins that regulate lipid biosynthesis), cause osteoblast (OB) differentiation abnormalities, and to test the functional significance of downstream target molecules during craniofacial bone formation. The long- term goal of this project is to gain insight into the mechanisms of craniofacial bone formation and provide new medications and diagnostic tools for bone diseases. We will test our working hypothesis by using mouse genetics and cellular biology approaches. In our preliminary studies, we found that: 1) impaired cholesterol synthesis resulted in accelerated bone formation; 2) excess cholesterol synthesis resulted in decreased bone formation; 3) the formation of primary cilia, which play a crucial in sensing cell signals, was altered in OBs from Dhcr7 knockout (KO) and neural crest specific Insig1/2 conditional knockout (cKO) mice; 4) WNT signaling was altered in Dhcr7 KO and Insig1/2 cKO mice; and 5) normalization of cholesterol metabolic aberrations restored craniofacial bone defects in Dhcr7 KO and Insig1/2 cKO mice. Our hypothesis that proper cholesterol metabolism is crucial for normal craniofacial bone formation will be tested in the following specific aims: 1) to determine the role of cholesterol metabolism in craniofacial bone development; and 2) to determine the role of cholesterol metabolism in primary cilium formation in bone. This study will unravel a new mechanism of bone development and homeostasis and will lead to innovative methods of diagnosis, treatment, and prevention of skull deformities.