Early intervention to restore OL and myelin development in leukodystrophy model

描述(申请人提供)：项目摘要：我们研究的目的是阐明髓鞘基因突变在少突胶质细胞(OL)细胞成熟和轴突包膜中的作用，这些突变的失败会导致髓鞘过少而导致脑白质营养不良。Canavan病(CD)就是这种脑白质营养不良症的一个例子，它是由天冬氨酸氨基转移酶(ASPA)基因的代谢性突变引起的。ASPA现在被认为是OL细胞的标志物，它代谢N-乙酰天冬氨酸(NAA)来释放醋酸酯和天冬氨酸。这种儿童疾病的病理生理包括海绵状白质形态、智力低下、巨脑、NAA酸尿、运动障碍和过早死亡。因为受Canavan病影响的幼儿表现出髓鞘功能低下，所以这个早期事件是否预示着OL功能障碍的问题就产生了。ASPA基因敲除(KO)小鼠品系缺乏ASPA蛋白和酶活性的表达，与人类CD的症状非常相似。我们的初步工作表明，尽管发现了髓鞘基因的转录本，但ASPA基因敲除的OL缺乏成熟的髓鞘碱性蛋白，并且在中枢神经系统的细胞突起中缺乏髓鞘蛋白的免疫染色。这表明，ASPA的表达在发育的早期阶段对于OL的成熟至关重要。此外，ASPA基因敲除小鼠的中枢神经系统也发生了大量的细胞凋亡。基因治疗被批准给另一组研究人员，他们在CD儿童队列中和在髓鞘形成高峰期后的CD啮齿动物模型中执行腺病毒相关病毒(AAV)介导的ASPA基因治疗。海绵状白质形态未见改善。在早期发育期间，OL祖细胞在胚胎中产生，而另一个OL谱系在出生后产生，以填充前脑。因此，我们建议针对这两个早期的OL群体进行ASPA基因的传递，以诱导OL成熟并在KO脑中发挥作用。这些发现将有助于理解ASPA在预防脑白质营养不良中的作用，并将有助于未来治疗的发展。 摘要简介：本提案的目的是恢复加那文病(CD)小鼠模型胚胎和出生后天冬氨酸氨基转移酶的活性。我们将证明该基因的活性对于髓鞘形成细胞的正常发育和轴突的包裹是至关重要的，而轴突的包裹对于正常的中枢神经系统功能是必不可少的。如果成功，这项研究的信息可以用来开发适当的治疗干预措施，用于治疗受CD影响的儿童，CD是导致智力低下和死亡的最具破坏性的疾病。

DESCRIPTION (provided by applicant): Abstract Project Summary: The objective of our research is to elucidate the role of myelin gene mutation on oligodendrocyte (OL) cell maturation and ensheathment of axons, failure of which results in hypomyelination that leads to leukodystrophy. Canavan disease (CD) is an example of such leukodystrophy which is caused by a metabolic mutation in aspartoacylase (ASPA) gene. Now recognized as a marker for OL cells, ASPA metabolizes N-acetyl aspartate (NAA) to release acetate and aspartic acid. The pathophysiology of this childhood disorder includes a spongy white matter morphology, mental retardation, megalencephaly, NAA aciduria, motor deficit, and early death. Because young children affected by Canavan disease display hypomyelination, the question arises whether this early event is indicative of OL dysfunction. An ASPA knockout (KO) mouse strain lacks expression of ASPA protein and enzyme activity, and closely resembles symptoms of human CD. Our preliminary work has shown that the ASPA knockout OLs exhibit lack of mature myelin basic proteins and lack of immunostaining of myelin proteins in cell processes in the CNS, even though presence of transcripts for myelin genes were identified. This suggests that expression of ASPA is critical during early stages of development for the maturation of OLs. In addition, a massive apoptotic cell death occurs in the CNS of ASPA knockout mice. Gene therapy was approved to another group of researchers, who administered an adenoviral-associated viral (AAV)-mediated ASPA gene therapy in a cohort of CD children, and in rodent models of CD after the peak period of myelination. No improvement in spongy white matter morphology was detected. During early development, OL progenitors arise embryonically, and yet another OL lineage is generated post- birth to populate the forebrain. Therefore, we propose to target these two early populations of OLs for delivery of ASPA gene to induce OL maturation and function in the KO brain. The findings will help understand the role of ASPA in prevention of leukodystrophy and will be useful for future development of therapies. Abstract Narrative: Objective of this proposal is to restore aspartoacylase activity during the embryonic and post-natal period of mouse model of Canavan Disease (CD). We will demonstrate that activity of this gene is critically necessary for the normal development of the myelin forming cells and the ensheathment of axons that is essential for normal CNS function. If successful, information from this study could be used to develop appropriate therapeutic interventions for the treatment of children affected by CD, the most devastating disease that causes mental retardation and death.