Functions of Neuroglycan C, Which Specific to the Central Nervous System, and its Application to the Neural Regeneration

神经聚糖C(NGC)，一种跨膜硫酸软骨素蛋白聚糖（PG），主要在大脑中表达。为了阐明NGC在大脑发育中的作用，我们计划通过有条件地靶向破坏NGC基因来产生NGC基因突变小鼠，这些小鼠的NGC基因表达异常。现在，我们有三种老鼠；NGC敲除小鼠的所有剪接变体都完全缺失，NGC敲除小鼠的NGC在大脑的各个区域表达下调，以及NGC敲除小鼠由于硫酸软骨素（CS）链结合位点的突变（S123A）而以非pg形式表达NGC。所有这些小鼠都是可繁殖的。组织化学研究表明，这些小鼠在大体脑解剖中没有表现出宏观异常。ngc敲除小鼠和ngc敲除小鼠在Morris水迷宫实验中均表现出明显的异常。NGC与学习和/或记忆有关我们已经报道了人脑中存在三种NGC剪接变体的转录本（NGC- i， -II和-III）。在本项目中，我们发现了另一个剪接变体NGC-IV的新转录本。我们可以通过Western blotting证明NGC-IV确实在海马的一些神经元细胞中表达，这与学习和/或记忆有关。此外，我们证实了NGC的另一种新转录物NGC- v在海马中表达。NGC是一种典型的兼职PG，在大脑发育过程中由PG形态转变为非PG形态。CS对NGC核心蛋白的修饰也受到不同细胞类型的不同调控。然而，CS链加入NGC核心蛋白的调控机制目前尚不清楚。在培养细胞中，我们证实应激反应蛋白GRP78可能与NGC的CS糖基化有关。

Neuroglycan C(NGC), a membrane-spanning chondroitin sulfate proteoglycan(PG) that is predominantly expressed in the brain. To clarify the role of NGC in development of the brain, we planned to generate NGC gene mutant mice, which show abnormal expressions of NGC by conditionally-targeted disruption of the NGC-gene. Now, we have gotten three strains of mice ; NGC-knockout mice that are completely deficient in all splice variants, NGC-knockdown mice in which the expression of NGC are down-regulated in various regions of the brain, and NGC-knockin mice that express NGC in non-PG form due to a mutation(S123A) at the chondroitin sulfate(CS) chain binding site. All these mice were viable and fertile. Histochemical studies showed that these mice did not show macroscopic abnormalities in gross brain anatomy. NGC-knockout mice displayed an obvious abnormality in Morris water maze test as well as NGC-knockdown mice, suggesting. that NGC is involved in learning and/or memory.We have reported that three transcripts for NGC splice variants(NGC-I, -II, and -III) exist in the human brain. In the present project, we discovered a new transcript for another splice variant, NGC-IV. We could demonstrate by Western blotting that NGC-IV was really expressed in some neuronal cells in the hippocampus, which is related to learning and/or memory. Furthermore, we demonstrated that NGC-V, another new transcript of NGC, was expressed in the hippocampus.NGC is a typical part-time PG that changes its structure from a PG form to a non-PG form during the development of the brain. Modification of the NGC core protein with CS is also differently regulated depending on cell types. However,the regulatory mechanism for the addition of the CS chain to NGC core protein is not known at present. In culture cells, we demonstrated that GRP78, one of stress-response proteins, might be related to CS glycosylation of NGC.