Natural genetic variation regulating infarct volume

描述（由申请人提供）：缺血性中风是由栓子或局部血栓形成引起的，并导致脑动脉闭塞区域的神经组织损伤（梗死）。目前对梗死损伤机制的理解主要基于实验模型。在基因操作的小鼠模型中，已经确定了几种基因/途径在诱导缺血时调节梗死的大小（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能提供有关自然疾病状态的机制的见解。基因缺失或转基因过度表达创造了一种人工生理状态，与自然发生的疾病中发现的状态相去甚远。我们建议使用QTL定位来识别涉及梗死的新基因/途径。在建立的局灶性脑缺血小鼠梗死模型中，不同近交系小鼠在梗死体积上表现出明显差异。我们已经完成了对这种表型的最大已知菌株调查。在每个菌株内和某些菌株之间，梗死体积的差异非常大（高达700%），可高度重现。我们利用这些差异来绘制梗死体积的自然遗传决定因素。在B6和BALB/c之间的F1交叉中，我们在7号染色体远端定位了一个位点，该位点对观察到的梗死体积变化贡献了50%以上。这种单一的天然等位基因对梗死体积的影响比大多数已发表的基因敲除或转基因细胞系所观察到的要大。我们已经用染色体替代菌株验证了这个位点的存在。此外，通过利用16个近交系的祖先单倍型共享模式，我们将该位点精细定位到仅覆盖6个基因的单倍型块。在这个应用中，我们建议使用分子遗传学和功能分析来鉴定7号染色体位点的基因。同时，我们建议利用CSS和同源系的解剖学和代谢研究来确定7号染色体位点背后的机制，从而分离出这个单一位点的影响。在最后的目标中，我们将绘制和鉴定同样强烈影响梗死体积的新基因，采用在7号染色体位点上没有差异的表型不同的自交系之间的杂交。新的、自然的调节梗死体积的等位基因的鉴定将为梗死的通路和机制提供新的和生理学相关的见解。从长远来看，这项工作可能为缺血性脑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.