Regulation of Extraocular Muscle Development

描述（由申请人提供）：Skeleton肌肉并不都是平等的。 肌肉前体细胞或成肌细胞不是具有预定命运的同质群体，而是代表来自各种胚胎来源的不同谱系。 外在因素与谱系相互作用，塑造发育中肌纤维的分子/细胞/结构特征。 眼外肌（EOM）在骨骼肌中是特别独特的。 我们的中心假设是，新的EOM表型的发展依赖于细胞自主和非细胞自主的调节机制，这两个共享和显着不同的决定成肌细胞的命运在其他骨骼肌。 具体来说，我们建议，独特的轨道环境和信号级联控制的组织特异性转录因子的神经相互作用直接EOM表达的EOM特异性，骨骼和心肌性状，使其适应广泛的动态生理范围所需的眼球运动控制系统。 一个核心问题是，丰富的数据从“传统”的肌肉研究是不够的，以解释独特的EOM属性的模式和规格。 我们最近的表达谱研究和EOM细胞系的发展提供了知识和工具，现在确定和直接测试EOM的调控机制。 具体目标1将解决EOM发展中的细胞自主调控机制，使用immortialized EOM和后肢肌肉细胞系结合基因/蛋白质表达谱。 具体目标2将研究转录因子Pitx 2在调节眼外肌发育的早期和晚期特征中的作用。 Pitx 2突变小鼠的等位基因系列将用于确定一般和纤维类型特异性性状调节的剂量依赖性。 具体目标3将确定轨道环境所特有的非细胞自主机制在形成EOM发展方面的作用。 我们的发现，眼外肌的生存器官型共培养依赖于眼运动神经元的神经支配将延长评估正确与不正确的运动神经元培养眼外肌的分子专业化。 该建议的健康相关性在于，明确需要了解EOM表型的分子规格，以便理解其独特的功能特征和对代谢和神经肌肉疾病的不同反应性。

DESCRIPTION (provided by applicant): Skeletal muscles are not all created equal. Muscle precursor cells or myoblasts are not a homogeneous population with a preordained fate, but rather represent distinct lineages derived from a variety of embryonic sources. Extrinsic factors interact with lineage in sculpting the molecular/cellular/structural traits of developing myofibers. The extraocular muscles (EOMs) are particularly unique among skeletal muscles. Our central hypothesis is that development of the novel EOM phenotype relies upon cell autonomous and non-cell autonomous regulatory mechanisms that are both shared with and strikingly divergent from those determining myoblast fates in other skeletal muscles. Specifically, we propose that neural interactions unique to the orbital environment and signaling cascades controlled by tissue-specific transcription factors direct EOM expression of a diverse array of EOM-specific, skeletal, and cardiac muscle traits that adapt it to the wide dynamic physiologic range required by eye movement control systems. A central problem is that the wealth of data from 'traditional' muscle studies is insufficient to explain the patterning and specification of distinctive EOM properties. Our recent expression profiling studies and development of an EOM cell line have provided the knowledge and tools to now identify and directly test EOM regulatory mechanisms. Specific Aim 1 will address cell autonomous regulatory mechanisms in EOM development, using immortialized EOM and hindlimb muscle cell lines in conjunction with gene/protein expression profiling. Specific Aim 2 will examine the role of the transcription factor, Pitx2, in regulating early and late features of EOM development. An allelic series of Pitx2 mutant mice will be used to determine dose dependence in regulation of both general and fiber type-specific traits. Specific Aim 3 will determine the role of a non-cell autonomous mechanism, unique to the orbital environment, in shaping EOM development. Our finding that EOM survival in organotypic co-culture is dependent upon oculomotor motoneuron innervation will be extended by assessing molecular specialization of EOM in culture with correct vs. incorrect motoneurons. The health relatedness of this proposal is that there is a clear need to understand the molecular specification of the EOM phenotype in order to comprehend both its unique functional features and differential responsiveness to metabolic and neuromuscular disease.