GENETIC ANALYSIS OF BONE MORPHOGENETIC PROTEINS

这项研究的长期目标是确定分子机制 控制骨骼组织的生长和形成这是一 这是高等动物发展中的一个普遍问题，特别是 与人类骨骼疾病诊断和治疗的相关性， 骨折这些研究特别旨在了解 骨形态发生蛋白（BMPs）在正常发育中的作用BMPs 最初是基于它们诱导软骨的能力而分离的， 当植入动物皮下时形成骨。的组合 BMP和载体基质足以诱导一个复杂的级联反应， 趋化和分化事件，最终导致 在异位身体部位形成充满骨髓的骨小骨。的 这些蛋白质在成熟骨骼中的存在，以及它们刺激 新骨形成，表明它们可能是骨形成的天然介质。 在胚胎发育和骨修复期间的骨生长和建模 骨折克隆研究表明，大多数BMP是一个 分泌的信号分子家族，其与 转化生长因子β骨形成蛋白是惊人的保守， 进化，与生物体中存在的近亲，如果蝇 果蝇因此，BMP样蛋白存在了至少一半的时间， 十亿年，必须早于骨骼的进化发明， 软骨果蝇中BMP基因同源物的突变破坏了 胚胎的背/腹模式，是致命的。这些发现， 与数据显示，哺乳动物BMP表达在许多 在小鼠发育过程中不同的组织，表明BMP可能发挥作用， 在高等动物中也扮演着不同的角色。直到最近， 已经可以用来测试骨形成蛋白在脊椎动物中的功能。但这 实验室最近表明，一种名为Bmp-5的BMP基因在 携带短耳基因突变的小鼠。基因完全丧失 与小鼠的完全活力和生育力相容，但与 具有骨骼异常的特定综合征，包括 外耳，一对肋骨的损失，大小的改变， 许多骨骼的形状，骨折修复中的缺陷，以及许多 软组织异常这种重要的小鼠突变提供了 第一个遗传模型，用于定义BMPs在发展中的作用， 更高的生物。拟议的研究将确定如何表达 Bmp-5的模式与突变小鼠中观察到的表型有关， BMP分子的结构域对正常功能最重要， 骨形成蛋白在骨骼外的作用。将定义顺式作用序列 控制Bmp-5骨诱导信号表达的时间和地点 在正常的发展过程中。最后，短耳小鼠将用于测试一种 一种新的利用克隆骨形态发生蛋白修复骨缺损的遗传学方法 基因.

The long term goal of this research is to define the molecular mechanisms that control the growth and patterning of skeletal tissue. This is a general problem in the development of higher animals, and is of particular relevance to the diagnosis and treatment of human skeletal diseases and bone fractures. The studies are particularly directed to understanding the role of bone morphogenetic proteins (BMPs) in normal development. BMPs were originally isolated based on their ability to induce cartilage and bone formation when implanted under the skin of animals. Combinations of BMPs and a carrier matrix are sufficient to induce a complex cascade of chemotactic and differentiation events that ultimately results in the formation of a marrow filled bony ossicle at ectopic body sites. The presence of these proteins in mature bones, and their ability to stimulate new bone formation, suggests that they may be the natural mediators of bone growth and modeling during embryonic development and repair of bone fractures. Cloning studies have shown that most BMPs are members of a family of secreted signaling molecules that have structural homology to transforming growth factor beta. The BMPs are strikingly conserved in evolution, with close relatives present in organisms such as the fruit fly Drosophila. BMP-like proteins have thus existed for at least a half billion years, and must predate the evolutionary invention of bone and cartilage. Mutations in a Drosophila homolog of a BMP gene disrupt early dorsal/ventral patterning of the embryo and are lethal. These findings, together with data showing that mammalian BMPs are expressed in many different tissues during mouse development, suggest that the BMPs may play diverse roles in higher animals as well. Until recently, no mutations have been available to test the function of BMPs in vertebrates. However, this laboratory has recently shown that a BMP gene called Bmp-5 is defective in mice carrying mutations at the short ear locus. Complete loss of the gene is compatible with full viability and fertility of mice, but is associated with a specific syndrome of skeletal abnormalities including reduction of the external ear, loss of one pair of ribs, alterations in the size and shape of many bones, defects in repair of bone fractures, and a number of soft tissue abnormalities. This important mouse mutation provides the first genetic model for defining the roles of BMPs in the development of higher organisms. The proposed studies will determine how the expression pattern of Bmp-5 is related to the phenotypes seen in mutant mice, which domains of BMP molecules are most important for normal function, and what roles BMPs play outside the skeleton. Cis-acting sequences will be defined that control when and where the Bmp-5 osteoinductive signal is expressed during normal development. Finally, short ear mice will be used to test a new genetic approach for correcting skeletal defects using cloned BMP genes.