Natural genetic variation regulating infarct volume

描述(申请人提供)：缺血性中风是由栓子或局部血栓形成引起的，并导致大脑动脉闭塞区域的神经组织损伤(脑梗塞)。目前对脑梗塞损伤机制的理解主要基于实验模型。在基因操纵的小鼠模型中，已经确定了几个基因/通路，它们在诱导脑缺血时调节梗塞的大小(体积)。不幸的是，仅基于基因敲除或转基因小鼠的证据并不总是提供对自然疾病状态涉及的机制的洞察。基因缺失或转基因过度表达创造了一种人工生理状态，这种状态可能与自然发生的疾病相去甚远。我们建议通过QTL定位来识别与脑梗塞相关的新基因/新途径。在已建立的局灶性脑缺血小鼠脑梗塞模型中，不同近交系小鼠在脑梗塞体积上表现出明显的差异。我们已经完成了这一表型的已知最大菌株调查。梗死体积的差异在每个品系内和某些品系之间的重复性很高，非常大(高达700%)。我们利用这些差异绘制了脑梗塞体积的自然遗传决定因素图。在B6和BALB/c的F1杂交中，我们在7号染色体远端定位了一个基因座，该基因座对观察到的脑梗塞体积变异的贡献率超过50%。这一单一的自然等位基因对脑梗塞体积的影响比大多数已发表的基因敲除或转基因株系的影响更大。我们已经使用染色体替代菌株验证了该基因座的存在。此外，通过利用16个近交系的祖先单倍型共享模式，我们已经将该基因座精细地定位到仅覆盖6个基因的单倍型块。在这一应用中，我们建议通过对这六个基因的分子遗传学和功能分析来确定7号染色体座位下的基因。同时，我们建议通过对CS和同源系的解剖学和代谢研究来确定7号染色体基因座背后的机制，从而分离出这个单一基因座的影响。在最终目标中，我们将利用表型不同的近交系之间的杂交，绘制和识别也强烈影响梗塞体积的新基因，这些近交系在7号染色体上没有不同。识别调节梗塞体积的新的、天然的等位基因将为研究梗塞的途径和机制提供新的和生理上相关的见解。从长远来看，这项工作可能为缺血性卒中的治疗干预提供新的靶点。 公共卫生相关性：缺血性中风会导致动脉阻塞部位附近的脑组织损伤(一种梗塞)。我们建议通过利用不同品系小鼠脑梗塞大小的自然差异来识别调节这一过程的基因。新基因的发现将为研究脑梗塞的途径和机制提供新的思路，并为缺血性卒中的治疗干预提供新的靶点。

DESCRIPTION (provided by applicant): Ischemic stroke is caused by an embolus or local thrombosis and results in neural tissue damage (an infarct) in the territory of the occluded cerebral artery. Current understanding of the mechanisms underlying infarct damage is based primarily on experimental models. Several genes/pathways have been identified that regulate the size (volume) of the infarct when ischemia is induced in genetically manipulated mouse models. Unfortunately, evidence based solely on gene knockout or transgenic mice does not always provide insight into mechanisms involved in the natural disease state. Gene deletion or transgenic over-expression creates an artificial physiologic state that can be far removed from that found in naturally occurring disease. We propose to identify novel genes/pathways involved in infarction using QTL mapping. In the well-established focal cerebral ischemia mouse model of infarction, different inbred mouse strains exhibit robust differences in infarct volume. We have completed the largest known strain survey for this phenotype. The differences in infarct volume are highly reproducible within each strain, and between certain strains, very large (up to 700%). We have exploited these differences to map a natural genetic determinant of infarct volume. In an F1 intercross between B6 and BALB/c, we have mapped a locus on distal chromosome 7 that contributes over 50% of the observed variation in infarct volume. This single natural allele shows an effect on infarct volume that is larger than that observed for most published knockout or transgenic lines. We have validated the presence of this locus using chromosome substitution strains. Furthermore, by exploiting ancestral haplotype sharing patterns in 16 inbred strains, we have fine-mapped this locus to haplotype blocks covering only six genes. In this application, we propose to identify the gene underlying the chromosome 7 locus using molecular genetic and functional assays for the six genes. In parallel, we propose to determine the mechanism behind the chromosome 7 locus using anatomic and metabolic studies of CSS and congenic lines that will isolate the effects of this single locus. In the final aim we will map and identify new genes that also strongly influence infarct volume, employing crosses between phenotypically divergent inbred strains that do not differ at the chromosome 7 locus. The identification of novel, natural alleles modulating infarct volume will provide new and physiologically relevant insight into the pathways and mechanisms involved in infarction. In the long-term, this work may provide novel targets for therapeutic intervention of ischemic stroke. PUBLIC HEALTH RELEVANCE: Ischemic stroke results in brain tissue damage (an infarct) near the site of the blocked artery. We propose to identify genes that regulate this process by exploiting natural variation in infarct size in different mouse strains. The identification of new genes regulating infarct size will provide new insight into the pathways and mechanisms involved in infarction, and in the long-term, provide novel targets for therapeutic intervention of ischemic stroke.