Creative biosynthesis mitigates pathogenesis in mdx mice

描述(由申请者提供)：本提案描述了NIAMS使命声明中详细说明的肌肉疾病研究领域的5年指导临床研究人员职业发展奖。医学博士/博士首席研究员是一名获得委员会认证的儿科神经科医生。他现在将通过独特的跨部门资源整合来扩展他的科学技能，并建立一个科学利基来构建学术生涯。该计划将通过扩展到分子和发育生物学以及小鼠分子遗传学，促进PI对杜氏肌营养不良症(DMD)的长期兴趣。李·尼斯旺德博士将指导主要研究人员的科学发展。作为Howard Hughes医学研究员，Niswander博士是发育生物学和小鼠遗传学领域公认的领导者，培养了大量博士后研究员、研究生和临床研究员。此外，一个由备受尊敬的肌肉科学家组成的咨询委员会将提供科学、临床和职业建议，帮助PI发展成为独立的调查员。PI处于整合不同资源的专业知识和利用多学科技术的理想环境中。研究将集中在Dstrophin缺陷MDX小鼠的肌酸从头合成假说上。PI发现，肌酸合成的关键酶--乙酸胍甲基转移酶(GAMT)在MDX骨骼肌中的mRNA和蛋白质水平均有差异上调。利用各种生化、分子、细胞和磁共振成像技术，具体目标包括：1)随着mdx小鼠GAMT的上调，最终产物肌酸也应该增加。然而，由于膜渗漏，肌酸水平的增加可能主要存在于尿液和血清中，而不是肌肉中，2)确定AGAT(肌酸合成所需的带有GAMT的前体酶)是否也在mdx肌肉的mRNA和蛋白质水平上上调，以及3)确定双空GAMTimdx小鼠的表型。这将是对MDX小鼠肌酸生物合成的第一次详细分析。目的是确定MDX小鼠是否合成从头肌酸作为一种适应，以减轻膜泄漏引起的代谢损害。肌营养不良蛋白是维持正常肌肉功能的重要蛋白质。患有DMD的男孩不会产生Dstrophin，随着时间的推移，他们的肌肉会变弱。MDX小鼠不会产生肌营养不良蛋白，但它们不会变得残废。这些研究可能会提供重要的线索，帮助寻找治疗DMD的新方法。

DESCRIPTION (provided by applicant): This proposal describes a 5 year Mentored Clinical Investigator Career Development Award in Muscle Diseases Research as detailed in the NIAMS mission statement. The MD/PhD principal investigator is a board-certified pediatric neurologist. He will now expand upon his scientific skills through a unique integration of interdepartmental resources and establish a scientific niche to construct an academic career. This program will promote the longstanding interest of the PI in Duchenne Muscular Dystrophy (DMD) by expanding into molecular and developmental biology and mouse molecular genetics. Dr. Lee Niswander will mentor the principal investigators scientific development. A Howard Hughes Medical Investigator, Dr. Niswander is a recognized leader in the field of developmental biology and mouse genetics and has trained numerous postdoctoral fellows, graduate students and clinical fellows. In addition, an advisory committee of highly-regarded muscle scientists will provide scientific, clinical and career advice to help the PI develop into an independent investigator. The PI is in an ideal setting to incorporate expertise from diverse resources and utilize multidisciplinary technologies. Research will focuses on the hypothesis of de novo creatine synthesis in dystrophin-deficient mdx mice. The PI has identified guanidineacetate methyltransferase (GAMT), the key enzyme for creatine synthesis as being differentially upregulated at both the mRNA and protein level in mdx skeletal muscle. Using an assortment of biochemical, molecular, cellular and magnetic resonance imaging techniques, the specific aims include: 1) As GAMT is upregulated in mdx mice, the end-product creatine should also be increased. However because of membrane leakage, increased creatine levels may be largely found in urine and serum, not muscle, 2) Determine if AGAT (the precursor enzyme with GAMT required for creatine synthesis), is also upregulated at the mRNA and protein level in mdx muscle, and 3) Determine the phenotype of a double-null GAMTimdx mouse. This will be the first detailed analysis of creatine biosynthesis in the mdx mouse. Objective is to determine if the mdx mouse synthesizes creatine de-novo as an adaptation to mitigate metabolic compromise caused by leaky membranes. Dystrophin is an important protein for normal muscle function. Boys with DMD do not make dystrophin and their muscles weaken over time. The mdx mice do not make dystrophin yet they do not become crippled. These studies may offer important clues that could help with new treatments for boys with DMD.