Early intervention to restore OL and myelin development in leukodystrophy model

项目简介：我们的研究目的是阐明髓磷脂基因突变在少突胶质细胞（OL）细胞成熟和轴突嵌套中的作用，这一过程的失败导致髓鞘化降低，从而导致脑白质营养不良。Canavan病（CD）是由天冬氨酸酰化酶（ASPA）基因的代谢性突变引起的白质营养不良的一个例子。现在被认为是OL细胞的标志物，ASPA代谢n -乙酰天冬氨酸（NAA）释放醋酸和天冬氨酸。这种儿童疾病的病理生理包括海绵状白质形态、智力迟钝、大脑畸形、NAA酸尿症、运动缺陷和早期死亡。由于受Canavan病影响的幼儿表现为髓鞘发育低下，因此出现了这个早期事件是否表明OL功能障碍的问题。ASPA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，ASPA敲除的OLs在中枢神经系统的细胞过程中缺乏成熟的髓磷脂基本蛋白和髓磷脂蛋白的免疫染色，尽管髓磷脂基因的转录本存在。这表明，在OLs成熟的早期发育阶段，ASPA的表达至关重要。此外，在ASPA基因敲除小鼠的中枢神经系统中出现大量凋亡细胞死亡。基因治疗被批准用于另一组研究人员，他们对一组乳糜泻儿童和髓鞘形成高峰期后的乳糜泻啮齿动物模型进行腺病毒相关病毒（AAV）介导的ASPA基因治疗。海绵样白质形态未见改善。在早期发育过程中，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，我们建议以这两个早期OL群体为目标，通过传递ASPA基因来诱导KO脑中OL的成熟和功能。这些发现将有助于理解ASPA在预防白质营养不良中的作用，并将对未来治疗的发展有用。

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.