Characterization of Myostatin and GDF-11

 描述(申请人提供)：我们的主要研究重点是了解两个高度相关的信号分子myostatin(MSTN，GDF-8)和GDF-11的生物学功能，这两个分子是我们在筛选新的转化生长因子家族成员时发现的。我们发现，缺乏MSTN的小鼠全身骨骼肌质量急剧增加，我们和其他人表明，全身给予MSTN抑制剂可以促进肌肉生长，表明MSTN在出生后限制肌肉生长。因此，人们对以MSTN为靶点以增强肌肉力量和再生能力产生了广泛的兴趣，至少有7家生物技术和制药公司正在进行第二/第三阶段的临床试验，在广泛的疾病环境中测试肌肉生长抑素抑制剂。我们发现GDF-11在轴型和肾脏发育中发挥重要作用，其他研究小组随后也表明GDF-11也调节神经系统和胰腺的发育。GDF11在成人组织中广泛表达，最近的研究表明GDF11可能在衰老过程中发挥重要作用。具体地说，循环中的GDF-11水平被报道随着年龄的增长而下降，给老年小鼠注射GDF-11蛋白被报道可以逆转与年龄相关的心脏、骨骼肌和神经系统的组织功能障碍。自那以后，其中一些发现受到了一篇论文的挑战，该论文报告称，GDF-11水平随着年龄的增长而增加，GDF-11对骨骼肌再生有不利影响。这些发现对MSTN和GDF-11在成年动物中的作用以及临床应用中操纵这些分子活性的潜在策略提出了新的问题。这方面的一个主要问题是，MSTN和GDF-11的不同功能是否反映了这些高度相关的分子之间固有的生化差异，或者它们的不同功能只是反映了它们不同的表达模式。这个项目的总体目标是了解这些分子不同功能的基础。这个项目是我们长期努力的延续，目的是了解MSTN和GDF-11的调控和信号机制，并将利用我们多年来开发的许多遗传和生化工具来针对这一调控网络的各个组成部分。具体目的是：比较MSTN和GDF-11在体外关于已知信号成分，包括抑制结合蛋白和受体的作用的活性；检测这些结合蛋白和受体在体内调节骨骼肌和心肌生长和功能以及骨骼肌再生中的作用；以及在小鼠身上进行基因敲入实验，其中MSTN编码序列被GDF-11取代(反之亦然)。这些实验的结果应该为了解不同生物功能的机制基础提供关键的见解。 MSTN和GDF-11在体内进行。我们相信，这些研究将对开发利用这些分子的活性进行治疗干预的策略至关重要。

 DESCRIPTION (provided by applicant): The main focus of our research has been to understand the biological functions of two highly related signaling molecules, myostatin (MSTN, GDF-8) and GDF-11, which we discovered in a screen for new transforming growth factor-ß family members. We showed that mice lacking MSTN have dramatic increases in skeletal muscle mass throughout the body, and we and others showed that systemic administration of MSTN inhibitors to mice can promote muscle growth, showing that MSTN acts to limit muscle growth postnatally. Hence, there is extensive interest in targeting MSTN to enhance muscle strength and regeneration, and at least 7 biotechnology and pharmaceutical companies are in phase II/III clinical trials testing myostatin inhibitors in a wide range of disease settings. We showed that GDF-11 plays an important role in axial patterning and in kidney development, and other groups subsequently showed that GDF-11 also regulates the development of the nervous system and pancreas. Gdf11 is expressed widely in adult tissues, and recent studies have suggested that GDF-11 may play an important role in aging. Specifically, circulating GDF-11 levels were reported to decrease with age, and administration of GDF-11 protein to aged mice was reported to reverse age-related tissue dysfunction in the heart, skeletal muscle, and nervous system. Some of these findings have since been challenged by a paper reporting that GDF-11 levels increase with aging and that GDF-11 has a detrimental effect on skeletal muscle regeneration. These findings have raised new questions regarding the roles of MSTN and GDF-11 in adult animals as well as the potential strategies for manipulating the activities of these molecules for clinical applications. A major question in this regard is whether the distinct functions of MSTN and GDF-11 reflect the inherent biochemical differences between these highly related molecules or whether their distinct functions simply reflect their differing pattern of expression. The overall goal of this project is to understand the basis for the distinct functios of these molecules. This project is a continuation of our long-standing effort to understand the mechanisms underlying the regulation and signaling of MSTN and GDF-11 and will utilize the many genetic and biochemical tools that we have developed over many years to target the various components of this regulatory network. The Specific Aims are: to compare the activities of MSTN and GDF-11 in vitro with respect to the roles of known signaling components, including inhibitory binding proteins and receptors; to examine the roles of these binding proteins and receptors in regulating skeletal and cardiac muscle growth and function and skeletal muscle regeneration in vivo; and to carry out gene knock-in experiments in mice in which the MSTN coding sequence is replaced with GDF-11 (and vice versa). The results of these experiments should provide key insights into the mechanistic basis underlying the distinct biological functions that MSTN and GDF-11 carry out in vivo. We believe that these studies will be crucial for developing strategies to exploit the activities of these molecules for therapeutic intervention.