The "olfactosome" as a biomolecular condensate

总结 生物分子凝聚物（BMC）代表了一种巧妙的生物解决方案， 简化生化过程而不产生独特的细胞器。从细胞质中的P体到 细胞核中的核仁和异染色质区室，核蛋白浓缩物的组装 提供了有效共调节基因表达和mRNA加工和翻译的手段。此外，本发明还 刺激诱导的凝聚物在细胞膜上的组装增强了 信号转导级联。因此，毫无疑问，BMC在神经元功能中起关键作用， 它们的失调会导致神经退化和其他神经系统疾病。在这里，我们采取 利用哺乳动物嗅觉系统的独特特性，为嗅觉系统建立了一个强大的范例。 严格剖析BMC在神经系统中的组装和功能。具体而言，我们建议， "嗅觉体"是一种多染色体增强体， 受体（OR）基因座代表BMC，其中分子拥挤诱导1/2800 OR等位基因的激活。 为了探索这一假设，我们将利用最近的一项技术突破， 神经元祖细胞，并将其分化为表达相同OR等位基因的嗅觉感觉神经元， 一种独特的方式，离体有了这个了不起的工具，我们建议对新生的OR RNA进行遗传标记， 会聚的染色体间增强子，以及存在于嗅觉体中的蛋白质。然后，我们将执行 现场成像单粒子跟踪（SPT）实验，将确定的动力学特性的 嗅觉体的核蛋白组分在这个多增强子枢纽的内部和外部以及可变的核 浓度的我们的实验将提供一个监管过程，这是必不可少的机械见解， 功能的嗅觉神经元和感官知觉，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， 从COVID-19感染到阿尔茨海默病， 根据我们的观察，源于嗅觉体的破坏，我们的研究将把基本的 在生物学上，重要的分子变化损害了神经元的功能。

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.