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，但理解变异形态学与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，可以解释表型变异在相似的基因型。该模型基于我们的初步数据，该数据显示了面部Sonic hedgehog （SHH）信号传导与连续表型变异之间的非线性关系。我们假设SHH通路活性的微小变化会产生巨大的表型变化，这些变化由于对通路活性受损的异质细胞反应而增加了方差。在本基金的第一个特定目标中，我们将重点研究非线性SHH信号对细胞反应变异的影响程度。这将在群体和单个细胞水平上进行。在第二和第三个特定目标中，我们将把注意力转移到分级SHH信号的体内遗传模型上。我们将检查产生的胚胎的表型，我们将确定表型的方差。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会增加。在本应用程序中设计的实验将直接测试这一预测，并将阐明破坏复杂发育系统稳定的潜在重要机制。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，在整个拨款中，使我们能够执行本应用程序中提出的分析。

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.