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母血症有关 胆固醇饮食会导致颅面部骨骼畸形，这表明胆固醇代谢异常可能 是颅面发育缺陷的一种广泛保守的机制。然而，它在很大程度上仍然是未知的。 胆固醇代谢改变如何导致头面部骨骼异常。因此，这样做的目的是 应用是通过破坏Dhcr7基因来确定胆固醇代谢异常 (它编码一种参与胆固醇合成最后一步的酶，是导致 Smith-Lemli-Opitz综合征)或Insig1和Insig2基因(它们为内质 调节脂质生物合成的网状蛋白)，导致成骨细胞(OB)分化异常，以及 检测下游靶分子在颅面骨形成过程中的功能意义。长的- 该项目的学期目标是深入了解颅面骨形成的机制，并提供新的 治疗骨病的药物和诊断工具。我们将使用鼠标来验证我们的工作假设 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)胆固醇受损 合成导致骨形成加速；2)过多的胆固醇合成导致骨骼减少。 3)在感知细胞信号中起关键作用的初生纤毛的形成从 Dhcr7基因敲除(KO)和神经峰特异性Insig1/2条件性基因敲除(CKO)小鼠；4)WNT信号转导 Dhcr7KO和Insig1/2 CKO小鼠的改变；5)胆固醇代谢异常的正常化 Dhcr7KO和Insig1/2 CKO小鼠颅面骨缺损的实验研究我们的假设是适当的胆固醇 新陈代谢对正常的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；以及2)确定 骨中初级纤毛形成过程中的胆固醇代谢。这项研究将揭开骨骼的一种新机制 发展和稳态，并将导致创新的诊断、治疗和预防方法 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.