NEUROBIOLOGY OF MARCKS--A MACS MUTANT MOUSE MODEL

MARCKS（富含豆蔻酰化丙氨酸的C激酶底物）是目前 脑中蛋白激酶C的主要磷蛋白底物。 积累的数据表明MARCKS在转导中的作用， 调节肌动蛋白膜可塑性的细胞外信号 以及与细胞内代谢的动态调节相关的细胞过程。 神经元细胞骨架和突触重构，例如，大脑 发育和神经递质信号传导。 其他证据来自 我们的实验室已经证明了MARCKS在海马体中的作用， 慢性锂在大脑中长期作用的目标。 与 最近建立的Macs基因突变小鼠模型， 现在已经在C57 BL/6背景上回交到第八代， MARCKS已被证明在大脑发育中起着关键作用。 我们实验室的最新数据首次证明 MARCKS mRNA在脑内的分布优先于 在大脑的边缘和边缘相关区域表达， 大鼠和小鼠海马内特异性细胞分布 个脑袋 在初步数据中，我们还证明了MARCKS是 在成人Macs null/+中以基因剂量依赖性方式表达 杂合子，并且MARCKS的大约50%的减少 表达与海马苔藓纤维增生有关， 以及增强的空间学习（第C.8b和C.9节）。 这些 根据我们目前的额外研究， 数据表明，显示海马苔藓的DBA/2小鼠 纤维发育不全和显著的空间学习缺陷，也表明 与C57 BL/6相比，海马MARCKS显著升高 小鼠该计划将进行为期三年的跨学科研究。 该战略与哺乳动物遗传学中心合作， 制造表达MARCKS水平从50%（Macs）到100%（Macs）不等的小鼠。 null/+）至野生型表达的260%（MARCKS Tg+/+） 小鼠 在这些小鼠中，我们将研究 海马苔藓纤维上MARCKS的低表达和高表达 发育、海马LTP电生理学和空间学习。 此外，我们还将评估这种中间菌株的遗传基础 MARCKS表达的变化，并确定 回交中控制MARCKS表达的数量性状基因座 和/或DBA/2和C57 BL/6的F2互交后代。 一旦基因 这种变化的基础是显而易见的，我们将确定是否相同的位点 与苔藓纤维锥体下投射的长度共分离 和空间学习在杂交后代中表达最高与最低 马克。 概述的一系列研究旨在检查一个直接的 MARCKS在海马神经可塑性事件中的作用 发展和学习/记忆，并评估在何种程度上，这些 复杂的表型性状与Macs基因本身和/或 相互作用的基因修饰剂。

MARCKS (Myristoylated Alanine Rich C Kinase Substrate) is the most prominent phosphoprotein substrate for protein kinase C in brain. Accumulating data have indicated a role for MARCKS in transducing extracellular signals for the regulation of actin-membrane plasticity and cellular processes associated with dynamic regulation of the neuronal cytoskeleton and synaptic restructuring, e.g., brain development and neurotransmitter signaling. Additional evidence from our laboratory has demonstrated a role for MARCKS in the hippocampus as a target for the long-term action of chronic lithium in the brain. With the recent creation of a mutant mouse model for the Macs gene which has now been backcrossed onto a C57BL/6 background to the eighth generation, MARCKS has been shown to play a critical role in brain development. Recent data from our laboratory have demonstrated for the first time that the distribution of MARCKS mRNA in brain is preferentially expressed in limbic and limbic-related regions of the brain, with a specific cellular distribution in hippocampus of both rat and mouse brain. In preliminary data, we have also demonstrated that MARCKS is expressed in a gene-dose dependent fashion in adult Macs null/+ heterozygotes, and that the approximately 50 percent reduction of MARCKS expression is associated with hippocampal mossy fiber hyperplasia, as well as enhanced spatial learning (Sections C.8b and C.9). These findings take on further significance in light of our current additional data demonstrating that DBA/2 mice which demonstrate hippocampal mossy fiber hypoplasia and significant spatial learning deficits, also show a significant elevation in hippocampal MARCKS as compared to C57BL/6 mice. This proposal outlines a three year interdisciplinary research strategy, in conjunction with the Center for Mammalian Genetics, to create mice expressing levels of MARCKS varying from 50 percent (Macs null/+) to 260 percent (MARCKS Tg+/+) of that expressed by wild-type mice. In these mice we will investigate the functional consequences of both under and over-expression of MARCKS on hippocampal mossy fiber development, hippocampal LTP electrophysiology, and spatial learning. In addition, we will assess the genetic basis of this interstrain variation in MARCKS expression and identify the positions of quantitative trait loci controlling MARCKS expression among backcross and/or F2 intercross progeny of DBA/2 and C57BL/6. Once the genetic basis of this variation is evident, we will determine if the same loci cosegregate with the length of the mossy fiber infrapyramidal projection and spatial learning in hybrid progeny expressing highest vs. lowest MARCKS. The outlined series of studies are designed to examine a direct role for MARCKS in neuroplastic events in brain related to hippocampal development and learning/memory, and assess the extent to which these complex phenotypic traits are linked to the Macs gene itself and/or interactive gene modifiers.