A transgenic model to study Bif-1 mediated neuroprotection in injury and disease

描述(由申请人提供)：越来越多的证据表明，线粒体功能障碍与影响大脑的损伤和疾病所观察到的神经退化有关，并与之有因果关系。虽然能量代谢和三磷酸腺苷的产生受到了极大的关注，但线粒体动力学的调节也出现了异常，这涉及到影响线粒体形状和大小的融合和分裂(碎裂)过程。重要的是，线粒体的融合和分裂直接涉及到确保它们的正确分布、运输和周转。考虑到将健康的线粒体定位在能量需求部位对神经元是多么重要，不难想象，损害线粒体分裂和融合调节的遗传或表观遗传修饰可能会产生不利影响 神经元的连接性、功能和生存能力。我们最近确定神经元表达两种交替剪接的线粒体分裂调节蛋白Bif-1(Bif-1b/c)。我们的初步数据显示，Bif-1b/c在大脑中动脉闭塞(MCAO，卒中模型)小鼠半暗带(大脑皮质)的神经元中丢失。重要的是，Bif-1缺失状态增强了MCAO引起的神经细胞死亡，以及培养中的DNA损伤和Aβ细胞毒作用。相反，Bif-1c的过度表达对Abeta介导的毒性具有显著的保护作用，这表明Bif-1是正常神经元功能所必需的。与老年匹配的非阿尔茨海默病(AD)患者相比，散发性阿尔茨海默病(AD)患者顶叶皮质(患区)和突触体内的Bif-1b/c蛋白显著减少。在APPswe/PS1dE9小鼠AD模型和加入有毒Abeta肽后的初级皮质神经元中，也观察到Bif-1b/c的这些变化。此外，在初步研究中，Bif-1基因缺失的小鼠在一岁时表现出显著的认知障碍，并且敲除Bif-1同系物(EndB)在果蝇中增强了基于眼睛表型的有毒Abeta42肽的毒性，但对表达无毒Abeta40肽的果蝇没有影响。这些发现证明了Bif-1的潜在神经保护功能，并提示与缺血性损伤和AD相关的线粒体功能障碍可能是由于Bif-1b/c表达减少所致。我们建议在可诱导的转基因小鼠神经元中恢复Bif-1c表达可促进神经元存活、保持线粒体完整性并增强对中风和AD小鼠模型的认知功能的假设。这些研究将确定Bif-1c是否具有减少伤害和疾病引起的损害的治疗作用。

DESCRIPTION (provided by applicant): Accumulating evidence demonstrates that mitochondrial dysfunction is both associated with and causally related to neurodegeneration observed in response to injury and diseases affecting the brain. While disturbances in energy metabolism and ATP production have received significant attention, abnormalities are also being found in the regulation of mitochondrial dynamics which involves the processes of fusion and fission (fragmentation) affecting the shape and size of mitochondria. Importantly, mitochondrial fusion and fission are directly involved in ensuring their proper distribution, transport, and turnover. Considering how vital it is for neurons to have healthy mitochondria positioned at sites of energy demand, it is not difficult to imagine that genetic or epigenetic modifications that impair the regulation of mitochondrial fission and fusion could adversely affect neuronal connectivity, function and viability. We recently determined that neurons express two alternatively spliced forms of a mitochondrial fission regulating protein, Bif-1 (Bif-1b/c). Our preliminary data demonstrates that Bif-1b/c is lost in neurons in the penumbra (cerebral cortex) of mice subjected to middle cerebral artery occlusion (MCAO, stroke model). Importantly, the Bif-1-null condition enhanced neuronal cell death caused by MCAO, and DNA damage and Abeta cytotoxicity in culture. Conversely, Bif-1c overexpression confers significant protection against Abeta-mediated toxicity indicating that Bif-1 is required for normal neuronal function. The Bif-1b/c protein is significantly reduced in the parietal cortex (affected area) and in synaptosomes of sporadic Alzheimer's disease (AD) patients compared to aged matched non-AD patients. These changes in Bif-1b/c are also observed in the APPswe/PS1dE9 mouse AD model and in primary cortical neurons following addition of the toxic Abeta peptide. Moreover, in preliminary studies, Bif-1-null mice displayed significant cognitive impairment at one year of age and knockout of the Bif-1 homologue (endoB) in drosophila enhanced the toxicity of the toxic Abeta42 peptide based on an eye phenotype, but had no effect on flies expressing the non-toxic Abeta40 peptide. These findings demonstrate a potential neuroprotective function of Bif-1 and suggest that mitochondrial dysfunction associated with ischemic damage and AD may be due to reduced expression of Bif-1b/c. We propose to test the hypothesis that restoration of Bif-1c expression in neurons in an inducible transgenic mouse promotes neuronal survival, retention of mitochondrial integrity and enhances cognitive function in response to stroke and in a mouse model of AD. These studies will determine if Bif-1c has therapeutic actions for reducing injury and disease-induced damage.