The "olfactosome" as a biomolecular condensate

摘要 生物分子缩合物(BMC)代表了一种巧妙的生物解决方案，可以解决组织和 简化生化过程，而不产生不同的细胞器。从细胞质中的P小体到 细胞核中的核仁和异染色室，核蛋白凝集物的组装 提供了有效地共同调节基因表达和信使核糖核酸的加工和翻译的手段。此外， 刺激诱导凝集物在细胞膜上的组装增强了 信号转导级联反应。因此，毫无疑问，骨髓细胞在神经元功能和 它们的错误调控会导致神经退行性变和其他神经疾病。在这里，我们带着 利用哺乳动物嗅觉系统的独特特性为 对BMC在神经系统中的组装和功能进行了严格的剖析。具体地说，我们建议 “嗅小体”是指在随机选择的嗅觉上组装的多染色体增强小体。 受体(OR)基因座，代表分子拥挤导致1/2800个OR等位基因激活的BMC。 为了探索这一假设，我们将利用最近的一项技术突破，使我们能够培养 并将其分化为嗅觉感觉神经元，表达相同的OR等位基因 一种独特的时尚，体外的。有了这个非凡的工具，我们建议将新生的OR RNA，即 聚合的染色体间增强子，以及驻留在嗅小体中的蛋白质。然后，我们将表演 实时成像单粒子跟踪(SPT)实验将确定 嗅小体在这个多增强子中心内外和可变核的核蛋白成分 浓度。我们的实验将提供对监管过程的机械性洞察，这对 嗅觉神经元和感觉的功能，并将产生广泛适用的原则 分子拥挤在高度合作的转录过程中的作用。重要的是，随着新的角色的出现 从新冠肺炎感染到阿尔茨海默氏症，人类的许多病理性疾病都存在嗅觉缺陷， 根据我们的观察，由于嗅小体的破坏，我们的研究将基本联系起来 生物学到损害神经元功能的翻译上重要的分子变化。

Summary Biomolecular condensates (BMCs) represent an ingenious biological solution to the problem of organizing and streamlining biochemical processes without generating distinct organelles. From P bodies in the cytoplasm to the nucleolus and heterochromatic compartments in the nucleus, the assembly of nucleoprotein condensates provides the means of efficiently co-regulating gene expression and mRNA processing and translation. Further, stimulus-induced assembly of condensates at the cell membrane enhances the specificity and robustness of signal transduction cascades. Thus, it is without doubt that BMCs play critical roles in neuronal functions and that their misregulation contributes to neurodegeneration and other neurological disorders. Here, we take advantage of the unique properties of the mammalian olfactory system to establish a powerful paradigm for the rigorous dissection of BMC assembly and function in the nervous system. Specifically, we propose that the “olfactosome,” the multi-chromosomal enhanceosome that assembles upon a randomly chosen olfactory receptor (OR) locus, represents a BMC in which molecular crowding induces the activation of 1/2800 OR alleles. To explore this hypothesis, we will take advantage of a recent technical breakthrough that allows us to culture neuronal progenitors and to differentiate them into olfactory sensory neurons that express the same OR allele in a singular fashion, ex vivo. With this remarkable tool, we propose to genetically label the nascent OR RNA, the converging inter-chromosomal enhancers, and the proteins residing in the olfactosome. Then, we will perform live imaging single particle tracking (SPT) experiments that will determine the kinetic properties of the nucleoprotein components of the olfactosome inside and outside this multi-enhancer hub and at variable nuclear concentrations. Our experiments will provide mechanistic insight to a regulatory process that is essential for the function of olfactory neurons and for sensory perception, and will generate widely applicable principles for the role of molecular crowding in highly cooperative transcriptional processes. Importantly, with the emerging role of olfactory deficits in a plethora of pathological human conditions, from COVID-19 infection to Alzheimer’s disease, which according to our observations, stem from the disruption of the olfactosome, our studies will link basic biology to translationally important molecular changes that impair neuronal function.