Natural genetic variation regulating infarct volume

描述（由申请人提供）：缺血性卒中由栓塞或局部血栓形成引起，并导致闭塞脑动脉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。在遗传操作的小鼠模型中，当诱导缺血时，已经鉴定了几种调节梗塞大小（体积）的基因/途径。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中所涉及的机制的深入了解。基因缺失或转基因过度表达产生了一种人工的生理状态，这种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定位来鉴定参与梗死的新基因/通路。在已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方面表现出显著差异。我们已经完成了对这种表型的最大的已知菌株调查。梗死体积的差异在每个菌株内是高度可重复的，并且在某些菌株之间非常大（高达700%）。我们已经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杂交中，我们绘制了远端7号染色体上的一个位点，该位点贡献了超过50%的观察到的梗死体积变化。这个单一的天然等位基因显示出对梗死体积的影响大于对大多数已发表的敲除或转基因品系所观察到的影响。我们已经使用染色体置换菌株验证了该位点的存在。此外，通过利用祖先的单倍型共享模式在16个近交系，我们已经精细映射这个位点的单倍型块覆盖只有6个基因。在本申请中，我们建议使用分子遗传学和功能测定的六个基因，以确定7号染色体位点的基因。同时，我们建议使用CSS和同类系的解剖和代谢研究来确定7号染色体位点背后的机制，这些研究将隔离这个单一位点的影响。在最后的目标，我们将映射和识别新的基因，也强烈影响梗死体积，采用表型不同的近交系之间的杂交，没有不同的染色体7位点。新的，自然的等位基因调节梗死体积的鉴定将提供新的和生理相关的洞察梗死的途径和机制。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：缺血性中风导致动脉阻塞部位附近的脑组织损伤（梗死）。我们建议通过利用不同小鼠品系中梗死面积的自然变化来确定调节这一过程的基因。新的梗死面积调控基因的发现将为梗死相关通路和机制的研究提供新的思路，并为缺血性卒中的长期治疗提供新的靶点。

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.