Analysis of transgenic mouse models for the role of polysialic acid and NCAM during brain development

糖基化与糖聚合物聚唾液酸（polySia）极大地改变了神经细胞粘附分子NCAM的结合特性。不能合成多肽的小鼠缺乏主要的脑轴突束。然而，这些缺陷可以通过额外消融polySia载体蛋白NCAM来修复。因此，为了保证正常发育，polySia似乎在关键时间窗口阻止NCAM相互作用。这个项目的目的是解决导致多纤缺乏症小鼠出现的大脑线路缺陷的分子和细胞机制。分析将在乳丘束进行，一个大的轴突束起源于乳房体，下丘脑核。由于其均匀的结构和可接近性，这个轴突束特别适合于计划的实验。首先，我们将在具有不同NCAM-和多唾液基转移酶设备的野生型和小鼠系中对其胚胎发育进行表征。然后，在子宫内电穿孔将用于诱导不同的NCAM亚型和不同的NCAM模块在polySia-和NCAM-阴性小鼠的乳腺体中的表达。这种治疗引起的发育缺陷将有助于得出与轴突寻路相关的ncam相互作用的结论。此外，已知的ncam介导的信号通路对多囊性下丘脑神经元轴突生长的潜在贡献将在外植体培养中进行研究。这些方法首次允许分析polySia对NCAM相互作用的控制如何指导大脑发育。

Glycosylation with the sugar polymer polysialic acid (polySia) drastically alters the binding properties of the neural cell adhesion molecule NCAM. Mice that are unable to synthesize polySia lack major brain axon tracts. These defects, however, can be rescued by additional ablation of the polySia carrier protein NCAM. Thus, to guarantee normal development, polySia seems to prevent NCAM interactions during critical time windows. The objective of this project is to resolve the molecular and cellular mechanisms leading to the brain wiring defects that appear in polySia-deficient mice. Analysis will be performed on the mamillothalamic tract, a large axonal bundle originating in the mammillary body, a hypothalamic nucleus. Due to its homogeneous structure and accessibility this axon tract is particularly suited for the kind of experiments planned. In a first step, its embryonic development in the wild-type and in mouse lines with different NCAM- and polysialyltransferase-equipment will be characterized. In utero electroporation will then be used to induce expression of different NCAM isoforms and different NCAM modules in the mammillary body of polySia- and NCAM-negative mice. Developmental defects induced by this treatment will allow drawing conclusions on the NCAM-interactions relevant for axonal pathfinding. Complementary, the potential contribution of known NCAM-mediated signaling pathways to axonal growth of polySia-deficient hypothalamic neurons will be studied in explant cultures. These approaches allow for the first time to analyze, how the control of NCAM interactions by polySia directs brain development.