Developmental mechanisms underlying genotype-phenotype correlations

描述(申请人提供)：表型变异是头面部出生缺陷的一个标志，但了解变异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，该模型可以解释相似基因类型中的表型差异。这个模型是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化之间的非线性关系。我们假设，SHH途径活性的微小变化会产生大的表型变化，这种变化会增加差异，这是由于细胞对受损的途径活性的不同反应。在这项拨款的第一个具体目标中，我们将重点研究非线性SHH信号在多大程度上促进细胞反应的变化。这将在群体和个体细胞水平上完成。在第二和第三个具体目标中，我们将把注意力转向分级SHH信号的体内遗传模型。我们将检查得到的胚胎的表型，并确定表型的差异。我们的模型预测，随着SHH信号中的非线性度的增加，产生大方差的可能性也会增加。本申请中设计的实验将直接检验这一预测，并将阐明一个潜在的重要机制，该机制破坏复杂的发育系统的稳定。在整个赠款中，使用几何形态计量学等定量分析与定量细胞分析和定量PCR相结合，使我们有能力执行本申请中提出的分析。 与公共卫生相关：面部结构畸形很常见，通常表现出很大程度的形态变异；然而，变异背后的机制尚不清楚。我们的目标是测试一个基于可能产生巨大表型差异的分子信号的非线性的模型。这项基础研究将有助于解释人类疾病最神秘的特征之一，并将允许对潜在治疗靶点进行更深入的机械探索。

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.