Modeling the complex genetics of congenital heart disease in mice

 描述(由申请人提供) 先天性心脏病(CHD)是最常见的出生缺陷之一，影响高达1%的活产。虽然CHD的各种证候形式的发现表明了一种遗传病因学，但CHD的遗传原因仍不清楚。由于人类群体的遗传变异性混淆了人类的遗传分析，我们最近在近交系C57BL6小鼠中进行了大规模的乙基亚硝胺(ENU)突变筛选，以恢复导致CHD的隐性突变。表型分型采用无创胎儿超声心动图，这是一种临床上用于冠心病诊断的成像手段。从100,000个胎儿的超声扫描中，我们获得了250个具有广泛冠心病谱的突变小鼠系。通过外显子组全序列分析，我们恢复了导致94个基因突变的150个CHD。令人惊讶的是，50%的CHD基因与纤毛相关，这表明纤毛在CHD发病机制中起着核心作用。同样出乎意料的是，许多纤毛相关的CHD基因编码已知的物理相互作用的蛋白质，这表明CHD的发病机制可能是在CHD相互作用组网络的背景下通过上位发生的假设。这可能导致与人类冠心病相关的复杂遗传学。为了验证这一假设，我们计划进行一种新的敏化筛查，首次系统地询问小鼠基因组中的半显性CHD突变。筛查将使用CEP290中的驱动突变进行，CEP290是在我们的隐性筛选中恢复的纤毛-CHD基因，在临床上也被很好地描述为在各种人类纤毛疾病和突变的小鼠模型中发挥遗传修饰效应。我们的筛查将需要对来自CEP290突变杂合子女性的G2胎儿进行超声扫描，以检测CEP290突变与G1男性杂合子交配的ENU诱导突变。由此产生的G2后代只能是CEP290和ENU诱导的突变的双重杂合子(除非ENU突变也在CEP290中)。因此，观察到的任何CHD都将反映上位性的影响。使用这一策略，我们希望从1800个G1家系中筛选出约54,000个胎儿，提供一种系统的方法来询问纤毛在CHD复杂遗传学中的作用，而隐性筛查是不可能的。突变恢复将使用小鼠全外显子组测序，然后进行基因分型分析，并进一步进行多个家系内和多个家系之间的连锁分析。为了验证筛查中发现的因果突变，将使用CRISPR/Cas9基因编辑生成转基因小鼠模型，然后与CEP290突变进行杂交，以检查上位性证据。总体而言，这一新的敏化筛选将首次系统地询问导致CHD的半显性突变的小鼠基因组。通过使用CEP290突变作为致敏筛查的驱动因素，我们可以进一步阐明纤毛在CHD发病机制中的作用。在这一敏化筛查中恢复的突变和动物模型将更好地模拟人类冠心病的复杂遗传学，并更好地为未来询问人类人群中冠心病的遗传学病因的临床研究提供信息。

 DESCRIPTION (provided by applicant) Congenital heart disease (CHD) is one of the most prevalent birth defects, affecting up to 1% of live births. While a genetic etiology is indicated by the finding of various syndromic forms of CHD, the genetic causes of CHD is still not well understood. As the genetic variability of the human population confounds human genetic analysis, we recently pursued a large scale ethylnitrosourea (ENU) mutagenesis screen in inbred C57BL6 mice to recover recessive mutations causing CHD. Phenotyping was conducted using noninvasive fetal echocardiography, an imaging modality used clinically for CHD diagnosis. From ultrasound scanning 100,000 fetuses, we recovered >250 CHD mutant mouse lines with a wide spectrum of CHD. We recovered 150 CHD causing mutations in 94 genes using whole exome sequencing analysis. Surprisingly, 50% of the CHD genes are cilia related, indicating a central role for cilia in CHD pathogenesis. Also unexpected was the recovery of many cilia related CHD genes encoding proteins known to physically interact, suggesting the hypothesis that CHD pathogenesis may occur via epistasis in the context of a CHD interactome network. This could contribute to the complex genetics associated with human CHD. To test this hypothesis, we plan to conduct a novel sensitized screen for the first systematic interrogation of the mouse genome for semi-dominant CHD mutations. The screen will be conducted using a driver mutation in Cep290, a cilia-CHD gene recovered in our recessive screen that is also clinically well described to exert genetic modifier effects, both in various human ciliopathies and in mutant mouse models. Our screen will entail ultrasound scanning G2 fetuses for CHD derived from females heterozygous for the Cep290 mutation mated to a G1 male heterozygous for ENU induced mutations. The resulting G2 offspring can only be double heterozygous for the Cep290 and ENU induced mutations (except when the ENU mutation is also in Cep290). Thus any CHD observed would reflect the effects of epistasis. Using this strategy, we expect to screen ~54,000 fetuses from 1800 G1 pedigrees, providing a systems approach to interrogate the role of cilia in the complex genetics of CHD not possible with a recessive screen. Mutation recovery will be carried out using whole mouse exome sequencing followed by genotyping analysis, and further linkage analysis conducted within and across multiple pedigrees. For validation of causal mutations identified in the screen, transgenic mouse models will be generated using CRISPR/Cas9 gene editing, followed by intercrosses with the Cep290 mutation to examine for evidence of epistasis. Overall, this novel sensitized screen will provide the first systematic interrogation of the mouse genome for semi-dominant mutations causing CHD. By using mutation in Cep290 as driver for this sensitized screen, we can further elucidate role of cilia in CHD pathogenesis. The mutations and animal models recovered in this sensitized screen will better model the complex genetics of human CHD and better inform future clinical studies interrogating the genetics etiology of CHD in the human population.