Sequence Variants Impacting Cardiomyocyte S-phase Activity in Inbred Mice Following Injury

大量研究表明，诱导心肌细胞的细胞周期活动， 对心肌梗死后心脏结构和功能的有益影响。还已显示 遗传背景可以影响小鼠心肌细胞周期活性的内在速率。我们观察到 具有DBA/2 J遗传背景的小鼠（简称DBA）的心肌细胞周期水平非常低， 心肌梗死后的活动。然而，当与C57 B16/NCR小鼠（缩写为NCR）杂交时， 得到的（DBA × NCR）-F1动物小鼠显示心肌细胞S-期活性显著增加， 梗死，表明NCR背景中存在常染色体基因（或多个基因）， 主要的方式来促进细胞周期的重新进入。对回交小鼠的分析表明， 位于位于3号染色体远端的感兴趣区域（ROI）。实验中提出的 目的1将检验ROI内的单个基因负责心肌细胞S期升高的假设 梗死后活动。该区域内的候选基因将根据表达模式进行鉴定 在梗塞的DBA与NCR心脏中观察到，以及预测影响 蛋白质结构和/或活性。候选人将通过产生转基因的 动物，使其发生心肌梗死，然后监测心肌细胞S期水平 活性;心肌细胞细胞周期活性的诱导将证实被测试的候选基因是 负责的特质。目标2中提出的实验将检验细胞周期升高 由NCR ROI等位基因编码的活性对降低的心脏功能和不利的心功能具有积极影响。 心肌梗死后出现的心肌重塑。DBA遗传背景中的同类小鼠， 保留3号染色体远端的杂合性，因此携带NCR等位基因（或多个等位基因）， 将产生心肌细胞S期诱导的主要贡献者。然后将小鼠置于 心肌梗死和纵向功能分析。最终分析将包括全面的 血液动力学测量以及不利的重构（心肌细胞凋亡， 心肌肥厚和心肌纤维化）;心脏功能和结构的相对改善表明， 心肌损伤后NCR编码的细胞周期活性的有益作用。最后，识别 并验证了在不同的心肌细胞中观察到的心肌细胞细胞周期速率内在差异的基因 小鼠品系可以提出潜在的治疗靶点，以增强受伤小鼠的再生生长。 心中

Numerous studies have shown that induction of cardiomyocyte cell cycle activity can have a profound beneficial impact on cardiac structure and function following myocardial infarction. It has also been shown that genetic background can impact the intrinsic rate of cardiomyocyte cell cycle activity in mice. We have observed that mice in a DBA/2J genetic background (abbreviated DBA) have very low levels of cardiomyocyte cell cycle activity following myocardial infarction. However, when crossed with C57Bl6/NCR mice (abbreviated NCR), the resulting (DBA x NCR)-F1 animals mice exhibit a marked increase in cardiomyocyte S-phase activity following infarction, indicating the presence of an autosomal gene (or genes) in the NCR background which acts in a dominant manner to facilitate cell cycle re-entry. Analysis of backcross mice established that this gene (or genes) resides in a region of interest (ROI) located on the distal end of chromosome 3. The experiments proposed in Aim 1 will test hypothesis that a single gene within the ROI is responsible for elevated cardiomyocyte S-phase activity post-infarction. Candidate genes within this region will be identified based on expression patterns observed in infarcted DBA vs. NCR hearts as well as by the presence of sequence variants predicted to impact protein structure and/or activity. The candidates will be systematically tested by generating genetically modified animals, subjecting them to myocardial infarction, and then monitoring the level of cardiomyocyte S-phase activity; an induction of cardiomyocyte cell cycle activity would confirm that the candidate gene being tested is responsible for the trait. The experiments proposed in Aim 2 will test the hypothesis that the elevated cell cycle activity encoded by the NCR ROI alleles has a positive impact on the diminished cardiac function and adverse myocardial remodeling which is encountered post-infarction. Congenic mice in a DBA genetic background which retain heterozygosity on the distal end of chromosome 3 and thus carry the NCR allele (or alleles) which is a major contributor to cardiomyocyte S-phase induction will be generated. The mice will then be subjected to myocardial infarction and longitudinal functional analysis. Terminal analyses will include comprehensive hemodynamic measurements as well as assessment of adverse remodeling (cardiomyocyte apoptosis, hypertrophy and myocardial fibrosis); relative improvements in cardiac function and structure would indicate a beneficial effect from the NCR-encoded cell cycle activity following myocardial injury. Ultimately, the identification and validation of genes underlying intrinsic differences in cardiomyocyte cell cycle rates observed in different strains of mice could suggest potential therapeutic targets with which to enhance regenerative growth in injured hearts.