Mouse Model of Myelin Basic Protein-Amyloid Beta Interactions in Brain

淀粉样β-蛋白（Ass）在脑中的积聚，无论是作为实质斑块还是 脑血管沉积是阿尔茨海默病（AD）患者的一个关键病理特征 以及几种相关的疾病Ass肽来源于淀粉样β蛋白 前体（AssPP）通过β-和ω-分泌酶的连续蛋白水解裂解。的 促进或阻碍Ass组装成存款于脑中的纤维结构的因子 在很大程度上是不确定的。我们实验室最近的体外研究表明， MBP蛋白是脑内髓鞘的主要成分，是一种有效的腺苷酸原纤维化抑制剂， 组装，并能保护培养的原代神经元免受Ass的毒性作用。虽然 脑中Ass的空间沉积与该发现一致（即富含MBP的脑白色物质 大部分没有纤维状的Ass沉积物），并且MBP降低与 水平和增加的屁股水平，它仍然是未知的，如果MBP确实影响屁股组装 和体内积累。 几种充分表征的人AssPP转基因小鼠模型已经被证实是一种新的动物模型。 产生AD样纤维状淀粉样沉积物。为了研究 在这些已建立的AssPP中，MBP对纤维状淀粉样蛋白组装和沉积的缺乏 转基因模型可以在MBP基因敲除的背景下培育它们。这样的 被称为“颤抖鼠标”的模型确实存在，但存在明显缺陷， 他们不形成髓磷脂，并在出生后几个月内死亡。不幸的是，人类的AssPP 转基因小鼠模型需要超过几个月的老化才能产生显著的 病理性淀粉样蛋白形成。不是敲除整个MBP蛋白的表达， 我们计划采用的一种更复杂的方法是突变一个高度特异性的结构域， MBP蛋白质上的一种特殊功能在R21阶段， 应用程序，我们建议生成一个新的“敲入”小鼠模型，我们将介绍 丙氨酸突变为内源性小鼠Golli-MBP基因中的特定KRG基序。我们 最近的研究已经鉴定了这种特异性KRG基序作为与Ass结合的必需元件 肽和抑制它们的纤维组装。由此产生的新的“敲门”模式将产生 MBP缺乏结合Ass肽并抑制其组装的能力。这些新的MBP- 将在小鼠中产生KRG/AAA敲除，并初步表征存活力、生长， 行为和髓鞘形成。 在成功完成此应用程序的R21阶段后，我们计划继续进行 在R33阶段，我们提出将小鼠中的MBP-KRG/AAA敲除与两种不同的 发展纤维状淀粉样蛋白沉积的人AssPP转基因小鼠模型。交叉 将小鼠品系老化并定量评价累积、吸收和 Ass肽的沉积和由此产生的下游病理和行为 后果这些研究的完成将为潜在的生理学研究提供新的见解。 控制致病性淀粉样蛋白组装的机制，并可能导致新的途径， 干预这一病理过程。

Accumulation of the amyloid ss-protein (Ass) in brain, either as parenchymal plaques or cerebrovascular deposits, is a key pathological feature of patients with Alzheimer's disease (AD) and several related disorders. The Ass peptides are derived from the amyloid ss-protein precursor (AssPP) by sequential proteolytic cleavages by ss- and ¿-secretase enzymes. The factors that either promote or impede Ass assembly into fibrillar structures that deposit in brain remain largely undefined. Recent in vitro work from our laboratory has shown that myelin basic protein (MBP), a prominent component of myelin in brain, is a potent inhibitor of Ass fibrillar assembly and can protect cultured primary neurons from the toxic effects of Ass. Although the spatial deposition of Ass in brain is consistent with this finding (i.e. brain white matter rich in MBP is largely devoid of fibrillar Ass deposits) and there is a relationship between decreased MBP levels and increased Ass levels it remains unknown if MBP does indeed influence Ass assembly and accumulation in vivo. Several well-characterized human AssPP transgenic mouse models have been generated that develop AD-like fibrillar amyloid deposits. To study the consequences of the absence of MBP on fibrillar amyloid assembly and deposition in these established AssPP transgenic models one could breed them onto an MBP gene knockout background. Such a model, known as the shiverer mouse, exists but comes with the significant shortcomings in that they do not form myelin and die within several months after birth. Unfortunately, human AssPP transgenic mouse models require aging well beyond several months to develop significant pathologic amyloid formation. Instead of knocking out expression of the entire MBP protein a more sophisticated approach that we plan to employ will be to mutate a highly specific domain on the MBP protein to disable a specific function. To this end, in the R21 Phase of this application we propose to generate a novel "knock in" mouse model where we will introduce alanine mutations into a specific KRG motif in the endogenous mouse Golli-MBP gene. Our recent studies have identified this specific KRG motif as an essential element for binding to Ass peptides and inhibiting their fibrillar assembly. The resulting new "knock in" model will produce MBP that lacks the ability to bind Ass peptides and inhibit their assembly. These novel MBP- KRG/AAA knock in mice will be generated and initially characterized for viability, growth, behavior, and myelination. After successful completion of the R21 Phase of this application we plan to proceed to the R33 Phase where we propose to cross the MBP-KRG/AAA knock in mice with two different human AssPP transgenic mouse models that develop fibrillar amyloid deposition. The crossed mouse lines will be aged and quantitatively evaluated for the acumulation, asembly, and deposition of Ass peptides and the resulting downstream pathological and behavioral consequences. Completion of these studies will provide new insight into potential physiological mechanisms that govern pathogenic amyloid assembly and may lead to new avenues for intervention into this pathologic process.