GENETIC ANALYSIS OF BONE MORPHOGENETIC PROTEINS

这项研究的长期目标是确定分子机制。 它们控制着骨骼组织的生长和图案。这是一个 高等动物发育过程中普遍存在的问题，具有特殊性 与人类骨骼疾病的诊断和治疗有关 骨折。这些研究特别针对了解 骨形态发生蛋白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出来的 当被植入动物的皮肤下时，骨形成。组合 BMP和载波矩阵足以引起复杂的级联 趋化和分化事件，最终导致 异位体部形成充满骨髓的骨小骨。这个 这些蛋白质在成熟骨骼中的存在及其刺激能力 新骨形成，表明它们可能是 胚胎发育和骨修复过程中的骨生长与建模 骨折。克隆研究表明，大多数BMP都是 具有结构同源性的分泌型信号分子家族 转化生长因子β。BMP被显著地保存在 进化，与近亲出现在有机体中，如果蝇 果蝇。因此，BMP样蛋白至少存在了一半。 亿万年前，它必须早于骨骼和 软骨。果蝇BMP基因同源物的突变早期中断 胚胎的背侧/腹侧花纹，是致命的。这些发现， 再加上数据显示哺乳动物的BMP在很多地方都有表达 小鼠发育过程中的不同组织，提示BMP可能在其中发挥作用 在高等动物中也有不同的角色。直到最近，还没有突变 可用于测试脊椎动物体内骨形成蛋白的功能。不过，这个 实验室最近发现，一种名为BMP-5的BMP基因在 携带短耳基因突变的小鼠。基因的完全丢失 与小鼠的完全存活和生育能力相兼容，但与 有一种特殊的骨骼异常综合征，包括 外耳，失去一对肋骨，大小和 许多骨骼的形状，骨折修复中的缺陷，以及一些 软组织异常。这种重要的小鼠突变提供了 第一个确定BMPs在骨质疏松症发生发展中作用的遗传模型 高等有机体。拟议的研究将确定如何表达 BMP-5的模式与突变小鼠中看到的表型有关， BMP分子的结构域对于正常功能是最重要的，什么 BMP在骨骼之外扮演的角色。将定义顺式作用序列 控制BMP-5成骨诱导信号表达的时间和地点 在正常发育过程中。最后，短耳老鼠将被用来测试一个 利用克隆骨形态发生蛋白修复骨缺陷的新遗传学方法 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.