Developmental mechanisms underlying genotype-phenotype correlations

描述（由申请人提供）：表型变异是颅面出生缺陷的标志，但了解可变形态和疾病之间的关系仍然难以捉摸。在这项工作中，我们建议测试一个模型，可以解释相似基因型内的表型变异。该模型基于我们的初步数据，显示了Sonic hedgehog（SHH）信号与面部连续表型变异之间的非线性关系。我们假设SHH通路活性的小变化产生大的表型变化，这些变化由于对受损通路活性的异质细胞反应而增加了方差。在本基金的第一个具体目标中，我们将重点研究非线性SHH信号对细胞反应变化的贡献程度。这将在群体和单个细胞水平上进行。在第二和第三个具体目标中，我们将把注意力转向分级SHH信号传导的体内遗传模型。我们将检查所得胚胎的表型，并确定表型的方差。我们的模型预测，随着SHH信号的非线性增加，产生大方差的可能性也增加。本申请中设计的实验将直接测试这一预测，并将阐明一个潜在的重要机制，使复杂的发育系统不稳定。定量分析的使用，如几何形态计量学与定量细胞测定和定量PCR相结合，在整个授权中，使我们有能力进行本申请中提出的分析。 公共卫生相关性：面部的结构畸形是常见的，并且经常表现出很大程度的形态学变化;然而，变化的机制尚不清楚。我们的目标是测试一个模型的基础上的非线性分子信号，可能会产生大的表型方差。这项基础研究将有助于解释人类疾病最神秘的特征之一，并将允许对潜在的治疗靶点进行更深入的机制探索。

DESCRIPTION (provided by applicant): Phenotypic variation is a hallmark of craniofacial birth defects, but understanding the relationship between variable morphology and disease remains elusive. In this work we propose to test a model that may explain phenotypic variation within similar genotypes. This model is based on our preliminary data showing a nonlinear relationship between Sonic hedgehog (SHH) signaling and continuous phenotypic variation in the face. We hypothesize that small changes in SHH pathway activity produce large phenotypic changes that have increased variance due to heterogeneous cellular responses to compromised pathway activity. In the first Specific Aim of this grant we will focus on examining the extent to which nonlinear SHH signaling contributes to variation in cellular response. This will be done at the population and the individual cell level. In the Second and Third Specific Aims we will turn our attention to in vivo genetic models of graded SHH signaling. We will examine the phenotype of resulting embryos and we will determine the variance of the phenotypes. Our model predicts that as the nonlinearity in SHH signaling increases the potential to produce large variance also increases. The experiments designed in this application will directly test this prediction and will illuminate a potentially important mechanism that destabilizes complex developmental systems. The use of quantitative analyses such as, geometric morphometrics coupled with quantitative cellular assays and quantitative PCR, throughout this grant gives us the power to perform the analyses proposed in this application. PUBLIC HEALTH RELEVANCE: Structural malformations of the face are common and often exhibit a large degree of morphologic variation; however, the mechanisms underlying variation are not known. Our objective is to test a model based on nonlinearities of molecular signaling that may produce large phenotypic variance. This basic research will help explain one of the most enigmatic features of human disease and will allow more in depth mechanistic explorations of potential therapeutic targets.