Thyroid Hormone Receptor Isoforms in Skeletal Muscle

描述(申请人提供)：骨骼肌中的干细胞在出生后肌肉的生长和损伤后的再生中起着重要的作用。有人提出，骨骼肌卫星细胞的命运可以从肌肉发生转变为脂肪发生，因此在几种病理情况下，如美国肌病、2型糖尿病、肥胖和年龄相关性骨质疏松症，骨骼肌卫星细胞可以促进异位肌肉内脂肪积累。在这项建议中，我们假设甲状腺激素受体(TR)亚型在体外和体内调节骨骼肌卫星细胞承诺和细胞命运规范。我们的初步观察表明，甲状腺激素受体在体外和体内对卫星细胞的增殖以及在体外向成肌和成脂细胞系的分化中都起着重要作用。此外，甲状腺激素受体在成脂分化中起作用，下调这种表达不会损害卫星细胞的增殖和 分化为功能性肌纤维。为了确认和进一步发展这些初步数据，我们计划对携带甲状腺激素抗性(RTH)相关突变的小鼠的原代肌肉卫星细胞进行体外研究。我们正在计划几项研究，致力于扩展我们在肌肉干细胞谱系分配的TR亚型调控的分子基础上的知识。我们将分析与卫星细胞自我更新和分化相关的转录因子以及与Wnt信号通路相关的基因和蛋白的表达。随后，我们将评估携带突变的肌肉卫星细胞移植到损伤前的肌肉中后的体内分化潜力。此外，我们还将利用遗传学和药理学工具，研究TR和？在骨骼肌损伤反应中的作用。这项资助中提出的工作将深入了解骨骼肌干细胞命运分配和肌肉内异位脂肪生成，以及TR亚型在调节这一过程中的可能作用。K08的申请提出了一个详细、全面的培训计划，允许申请者继续与她的研究和职业目标相关的学习。一支优秀的导师团队将从多个角度和正在进行的研究的各个方面直接监督研究培训。最终目标是申请者利用在此授权期内获得的数据来成功地申请R01。这将允许申请者成为内分泌学领域的一名独立资助的内科科学家，搭建干细胞研究的桥梁。

DESCRIPTION (provided by applicant): Stem cells resident in the skeletal muscle play an important role in postnatal muscle growth and regeneration after injury. It has been proposed that skeletal muscle satellite cell fate can be switched from myogenesis to adipogenesis and for this reason contribute to ectopic intra-muscle fat accumulation in several pathological condition such us myopathy, type 2 diabetes, obesity, and age-related sarcopenia. In this proposal we hypothesize that thyroid hormone receptor (TR) isoforms modulate skeletal muscle satellite cell commitment and cell fate specification in vitro and in vivo. Our preliminary observations demonstrate that thyroid hormone receptor ¿ (TR¿) has an important role both in proliferation of satellite cells in vitro and in vivo and in their differentiation to myogenic and adipogenic cell lineages in vitro. In addition thyroid hormone receptor ¿ (TR¿) plays a role in adipogenic differentiation and knocking down this expression does not impair satellite cells proliferation and differentiation into functional myofibers. To confirm and further develop these preliminary data, we plan to conduct in vitro study on primary muscle satellite cells derived from mice carrying a Resistance to Thyroid Hormone (RTH)-associate mutation for TR¿ and TR¿. We are planning several studies devoted to extend our knowledge on molecular basis of TR isoform regulation of muscle stem cell lineage allocation. We will analyze gene and protein expressions associated with transcription factors for self-renewal and differentiation of satellite cell and associated wih Wnt signaling pathway. Subsequently we will evaluate the in vivo differentiation potential of muscle satellite cell carrying a TR ¿ or ¿ mutation after transplantation into preinjured muscles. In addition, we will investigate the role of TR ¿ and ¿ in skeletal muscle response to injury by utilizing both genetic and pharmacologic tools. The work proposed in this grant will provide insight into skeletal muscle stem cell fate allocation and intra-muscle ectopic adipogenesis and the possible role of TR isoforms in modulating this process. The K08 application proposed a detailed, comprehensive training plan that will allow the applicant to pursue studies related to her research and career goals. An outstanding team of mentors will directly oversee the research training in various angles and all the aspects of research in progress. The ultimate goal is for the applicant to leverage the data obtained during this grant period into a successful R01 application. This will then allow the applicant to become an independently-funded physician-scientist in the field of endocrinology bridging stem cell research.