TWITCHER--A MODEL OF A HUMAN GENETIC NEUROLOGIC DISORDER

抽动者是最近发现的小鼠的一种神经学突变。 潜在的遗传缺陷是半乳糖基神经酰胺酶缺乏。这个 因此，Twitcher是一种从基因和酶学上可信的模型 人类球状细胞白质营养不良症(Krabbe病)。现在 应用建议为遗传学研究探索这一模式 半乳糖神经酰胺酶缺乏症，绕过稀有性和伦理性 人类疾病的制约。该研究计划包括三个主要部分 目标。第一个目标是描述Twitcher模型的特征 在成分上和代谢上。详细的成分分析 大脑、周围神经和肾脏的发育将通过 特别强调糖脂组成，糖脂的组成 髓鞘，以及半乳糖鞘氨醇的可能积累 (精神病)。还将对该突变体进行酶学鉴定。这个 代谢特征将包括半乳糖神经酰胺的合成 在体内和体外，在大脑和肾脏中。形成和形成了 对髓鞘的维护也将进行放射性研究。 先驱物。这些基本特性实验的结果将 与现有的人类患者数据进行比较，因为人们不能忽视 潜在的物种差异，即使疾病是由相同的 酶缺乏症。第二个主要目标涉及提纯 正常小鼠半乳糖基神经酰胺酶及其突变体的纯化 (不活跃的)酶。最后的主要目标是探索以下几种途径 通过补充酶来纠正遗传缺陷。神经移植 实验，正常组织和骨的脑内移植 骨髓移植计划用于活体实验。此外, 外源、部分纯化的半乳糖基神经酰胺酶的作用 与正常组织的共培养将在器官类型培养中进行检验。 抽动的脊髓。酶的科学意义 目前，补充研究更多的是基础性的发展 神经生物学，而不是在不久的将来临床应用。

The twitcher is a recently discovered neurological mutant of the mouse. The underlying genetic defect is a deficiency of galactosylceramidase. The twitcher therefore is a genetically and enzymatically authentic model of human globoid cell leukodystrophy (Krabbe disease). The present application proposes to explore this model for studies of genetic galactosylceramidase deficiency, bypassing the rarity and the ethical constraints of the human disease. The research plan contains three major goals. The first goal is to characterize the twitcher model compositionally and metabolically. Detailed compositional analysis of developing brain, peripheral nerves and kidney will be carried out with a particular emphasis on the glycolipid composition, the compostion of myelin, and on the possible accumulation of galactosylsphingosine (psychosine). The mutant will also be characterized enzymatically. The metabolic characterization will include synthesis of galactosylceramide in vivo and in vitro, both in the brain and kidney. The formation and maintenance of the myelin sheath will also be studied with radioactive precursors. The results of these basic characterization experiments will be compared with available data on human patients, since one cannot ignore potential species differences even though the disease is caused by the same enzymatic deficiency. The second major goal involves purification of the normal mouse galactosylceramidase and attempts at purifying the mutant (inactive) enzyme. The final major goal is to explore several avenues of correction of the genetic defect by enzyme supplementation. Nerve graft experiments, intracerebral tranplantation of normal tissues, and bone marrow transplantation are planned for in vivo experiments. In addition, effects of exogenous, partially purified galactosylceramidase and of co-culture with normal tissues will be examined in the organotypic cultures of the twitcher spinal cord. The scientific significance of the enzyme supplementation studies is, at present, more of fundamental developmental neurobiology, rather than of clinical applications in the near future.