Phenotypic variability due to genetic buffering: The role of environmental factors

遗传因素可以诱导和促进疾病和衰老表型的发展。孟德尔描述的显性和隐性遗传模式代表了一系列状态的极端。已经证明，有害的遗传变异的影响，预计会导致严重的表型，可以被细胞缓冲，从而减轻所产生的表型。这一过程被称为遗传缓冲，它基于不同的机制，如遗传补偿、转录适应和表型可塑性。已知有助于遗传缓冲的因素在某种程度上被认为是非遗传的，但在这方面的知识很少。在目前的应用中，我们假设遗传缓冲受到环境条件变化的影响。基因缓冲通常通过修饰基因的表达来实现。杜氏肌营养不良症（DMD）是一种罕见的由肌营养不良蛋白基因突变引起的遗传病，其中一个例子就是Utrophin在杜氏肌营养不良症（DMD）患者中的上调。我们想要阐明遗传缓冲和修饰基因的调控是否以及如何受到环境因素的影响。为此，我们已经生成并表征了人类诱导多能干细胞（iPSCs）和相应的突变体，这些突变体在分子水平上概括了DMD和肌动蛋白b （ACTB）相关综合征，即具有广泛表型差异的人类单基因疾病。分别通过RNA测序和qPCR分析鉴定和验证了相应的修饰基因。在应用研究项目中，我们将生成的iPSCs暴露于亚毒性和低毒浓度的暴露相关环境因素（空气污染物、食品污染物）中，并评估它们对修饰基因表达的影响。鉴于所有应用的环境因素都可能刺激活性氧的产生，并且氧化应激能够调节基因的表达，包括修饰基因，在啮齿动物疾病模型中，我们期望发现修饰基因表达模式的深刻变化。接下来，我们将通过关注对修饰基因调控或遗传补偿机制的直接影响来评估潜在的作用模式。特别是，我们将在核酸分辨率下研究暴露于环境污染物的影响，即通过分析表观遗传DNA和外转录组RNA修饰以及全局转录组。鉴于基因缓冲和修饰基因的调节与临床相关，将筛选可能调节环境敏感修饰基因的小分子文库。这些研究将为遗传缓冲的环境因素的相关性提供基本的见解。

Genetic factors can induce and contribute to the development of diseases and aging phenotypes. The dominant and recessive genetic patterns of inheritance described by Mendel represent the extremes of a spectrum of states. It has been demonstrated that the effects of deleterious genetic variations, which would be expected to cause severe phenotypes, can be buffered by cells, thereby mitigating the resulting phenotype. This process known as genetic buffering is based on different mechanisms, such as genetic compensation, transcriptional adaptation and phenotypic plasticity. The factors which are known to contribute to genetic buffering are, in part, thought to be non-genetic in nature, but knowledge in this regard is scarce.In the present application, we postulate that genetic buffering is affected by changing environmental conditions. Genetic buffering is often achieved through the expression of modifier genes. One example is the upregulation of Utrophin in patients with Duchenne muscular dystrophy (DMD), a rare genetic disorder caused by mutations of the dystrophin gene. We want to elucidate whether and how genetic buffering and the regulation of modifier genes are influenced by environmental factors. To this end, we already generated and characterized human induced pluripotent stem cells (iPSCs) and respective mutants which recapitulate, at a molecular level, DMD and Actin-B (ACTB)-associated syndromes, i.e. human monogenic diseases with a wide phenotypic variance. The corresponding modifier genes were identified and validated by RNA sequencing and qPCR analyses, respectively. In the applied research project, we will expose the generated iPSCs to sub-toxic and low toxic concentrations of exposure-relevant environmental factors (air pollutants, food contaminants) and assess their impact on the expression of modifier genes. Given that all of the applied environmental factors may stimulate the generation of reactive oxygen species, and oxidative stress is capable of modulating the expression of genes, incl. including modifier genes, in rodent disease models, we expect to find profound alterations in the expression pattern of the modifier genes. We will next assess the underlying mode of action by focusing on direct effects either on modifier gene regulation or on the genetic compensation machinery. Particularly, we will investigate the effect of the exposure to environmental pollutants at nucleic acid resolution, i.e. by analyzing epigenetic DNA- and epitranscriptomic RNA modifications as well as the global transcriptome. Given that the modulation of genetic buffering and modifier genes is clinically relevant, libraries of small molecules which may modulate the environmentally-susceptible modifiers, will be screened. These studies will provide fundamental insights into the relevance of environmental factors for genetic buffering.