Crtap function during skeletal homeostasis

描述（由申请人提供）： 骨质疏松症是一种常见的骨骼疾病，其特征在于低骨量和微结构的恶化，从而增加骨脆性和对骨折的易感性。原发性骨质疏松症可能是由于在青春期和成年早期达到较低的峰值骨量，和/或由于骨形成和骨吸收之间的不平衡。遗传因素是这一过程的主要决定因素，动物模型对于识别在这一过程中发挥作用的新基因和途径非常有帮助。这项提案的重点是一个新的基因，可能是重要的一个关键途径，调节骨形成，纤维胶原的合成。为了鉴定调节软骨和骨形成的新基因，我们先前通过体外培养的软骨细胞的差异筛选鉴定了一个基因，并将其命名为Crtap（Cartilage Associated Protein，软骨相关蛋白）。为了了解其在体内的功能，我们产生了Crtap基因的无效突变小鼠。我们的初步观察表明，Crtap敲除小鼠出现严重的早发性骨质疏松症和年龄相关性脊柱后凸。为了了解Crtap基因的功能特征，我们建议系统地分析在骨骼形成和稳态过程中Crtap功能丧失的后果。首先，将进行组织学、组织形态学、显微CT和生化分析，以更好地表征Crtap-/-小鼠的骨骼表型，从而确定骨缺损是否继发于骨形成和/或骨吸收失调。第二，我们将在体外对成骨细胞和破骨细胞的原代培养物进行功能研究，以确定细胞自主缺陷。这些初步实验有望开始阐明Crtap基因在骨形成和稳态过程中的功能及其在骨质疏松症发病机制中的作用。重要的是，他们可以确定胶原蛋白翻译后修饰，折叠，组装或分泌的新调节因子。

DESCRIPTION (provided by applicant): Osteoporosis is a common bone disease characterized by low bone mass and deterioration in the microarchitecture, with a consequent increase in bone fragility and susceptibility to fractures. Primary osteoporosis can be due to attainment of lower peak bone mass during puberty and early adulthood, and/or to an unbalance between bone formation and bone resorption. Genetic factors are a primary determinant of this and animal models have been extremely helpful for identifying new genes and pathways that play a role in this process. This proposal focuses on a novel gene that could be important in a crucial pathway that regulates bone formation, the synthesis of fibrillar collagens. In an effort to identify new gene in the regulation of cartilage and bone formation, we previously identified a gene by differential screening of in vitro cultured chondrocytes and named it Crtap (Cartilage Associated Protein). To understand its in vivo function, we generated a null mutant mouse for the Crtap gene. Our initial observations show that the Crtap null mice develop a severe early onset osteoporosis and age-related kyphosis. To comprehend the functional characteristics of the Crtap gene we propose to systematically analyze the consequences of Crtap loss of function during skeletal formation and homeostasis. First, histological, histomorphometric, micro-CT and biochemical analyses will be performed to better characterize the skeletal phenotype of the Crtap-/- mice and hence determine whether the bone defect is secondary to dysregulated bone formation and/or bone resorption. Second, we will perform functional in vitro studies on primary cultures of osteoblasts and osteoclasts in order to identify cell-autonomous defects. These initial experiments are expected to begin elucidating the function of the Crtap gene during bone formation and homeostasis and its role in the pathogenesis of osteoporosis. Importantly, they may identify a new regulator of collagen post-translational modification, folding, assembly or secretion.