Systems Genetics of Osteoblast Activity

描述（由申请人提供）：骨质疏松症是一种进行性骨丢失疾病，导致骨骼脆弱和易骨折。这种疾病影响约1200万美国人，是美国社会的主要医疗和经济负担。骨质疏松症主要是一种遗传性疾病，具有骨折预测特征，如骨矿物质密度（BMD），是最高度遗传的疾病相关表型之一。在人类和小鼠中，迄今为止的遗传研究几乎完全集中在BMD的分析上。然而，骨密度是一个复杂的生物体水平的特点，是由一个复杂的遗传和环境因素的环境影响。这阻碍了我们精确识别因果基因的能力，更重要的是，阻碍了我们精确识别作为遗传关联基础的它们的作用机制的能力。作为一种替代方案，我们建议专注于一个更简单的细胞水平的过程，成骨细胞介导的骨形成的遗传学。这个建议的目的是确定影响成骨细胞功能的基因。这将使用称为协作交叉（CC）的新型和创新的小鼠遗传参考群体来完成。在一项初步研究中，我们使用全基因组关联作图确定了小鼠Chr 4上成骨细胞介导的骨形成的遗传位点，并确定Wnt 4是该位点的候选基因。在目的1中，我们将评估调节Wnt 4表达水平对体外成骨细胞功能的影响以及删除Wnt 4对体内骨量和强度的影响。在目标2中，我们将绘制额外的高分辨率的数量性状位点（QTL）矿化结节形成，成骨细胞介导的骨形成的生理相关措施，在CC。在目标3中，我们将从QTL转移到矿化结节形成QTL的候选基因的鉴定和验证。这将通过利用CC的独特遗传方面来实现，以在生物信息学上缩小这些基因座，然后进行RNA-seq/表达QTL研究以进一步确定致病基因。矿化结节形成QTL的候选基因将通过基因过表达和敲除研究进行测试。我们希望对细胞水平过程的研究将提供更有效地从基因座到基因再到机制的方法。Wnt 4和其他将被鉴定的基因将作为潜在的治疗靶点，能够在骨质疏松症的背景下增加骨形成。

DESCRIPTION (provided by applicant): Osteoporosis is a disease of progressive bone loss, leading to weak and fracture prone bones. This disease affects ~12 million Americans and is a major medical and economic burden on American society. Osteoporosis is primarily a genetic disorder with fracture predicting traits, such as bone mineral density (BMD), being among the most highly heritable disease associated phenotypes. In humans and mice, genetic studies to date have almost exclusively focused on the analysis of BMD. However, BMD is a complex organismal- level trait that is influenced by a complicated milieu of genetic and environmental factors. This has hampered our ability to precisely identify the causal genes, and more importantly, their mechanisms of action, that underlie genetic associations. As an alternative, we propose to focus exclusively on the genetics of a more 'simple' cell-level process, osteoblast-mediated bone formation. The objective of this proposal is to identify genes affecting osteoblast function. This will be accomplished using a novel and innovative mouse genetic reference population termed the Collaborative Cross (CC). In a pilot study, we identified a genetic locus on mouse Chr 4 for osteoblast-mediated bone formation using genome-wide association mapping and determined that Wnt4 was the candidate gene for this locus. In Aim 1, we will evaluate the effect of modulating expression levels of Wnt4 on osteoblast function in vitro and the effects of deleting Wnt4 on bone mass and strength in vivo. In Aim 2, we will map additional high-resolution quantitative trait loci (QTL) for mineralized nodule formation, a physiologically relevant measure of osteoblast-mediated bone formation, in the CC. In Aim 3, we will move from QTL to the identification of and validation of candidate genes for mineralized nodule formation QTL. This will be accomplished by exploiting the unique genetic aspects of the CC to bioinformatically narrow these loci, followed by RNA-seq/expression QTL studies to further pin point causative genes. Candidate genes for mineralized nodule formation QTL will be tested by gene overexpression and knockdown studies. We expect that the study of a cell-level process will provide the means to more efficiently go from locus to gene to mechanism. Wnt4 and additional genes that will be identified will serve as potential therapeutic targets capable of increasing bone formation in the setting of osteoporosis.