The idea that liquid-liquid phase separation (LLPS) may be a general mechanism by which molecules in the complex cellular milieu may self-organize has generated much excitement and fervor in the cell biology community. While this concept is not new, its rise to preeminence has resulted in renewed interest in the mechanisms that shape and drive diverse cellular self-assembly processes from gene expression to cell division to stress responses. In vitro biochemical data have been instrumental in deriving some of the fundamental principles and molecular grammar by which biological molecules may phase separate, and the molecular basis of these interactions. Definitive evidence is lacking as to whether the same principles apply in the physiological environment inside living cells. In this Perspective, we analyze the evidence supporting phase separation in vivo across multiple cellular processes. We find that the evidence for in vivo LLPS is often phenomenological and inadequate to discriminate between phase separation and other possible mechanisms. Moreover, the causal relationship and functional consequences of LLPS in vivo are even more elusive. We underscore the importance of performing quantitative measurements on proteins in their endogenous state and physiological abundance, as well as make recommendations for experiments that may yield more conclusive results.

中文翻译：

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评估活细胞中的相分离：诊断、注意事项和功能后果。


液-液相分离（LLPS）可能是复杂细胞环境中分子自我组织的一种通用机制，这一想法在细胞生物学界引起了极大的兴奋和热情。虽然这个概念并不新鲜，但它的崛起引起了人们对塑造和驱动从基因表达到细胞分裂再到应激反应等多种细胞自组装过程的机制的新兴趣。体外生化数据有助于推导生物分子相分离的一些基本原理和分子语法，以及这些相互作用的分子基础。关于相同原理是否适用于活细胞内的生理环境，缺乏确凿的证据。在本视角中，我们分析了支持跨多个细胞过程的体内相分离的证据。我们发现体内 LLPS 的证据通常是现象学的，不足以区分相分离和其他可能的机制。此外，LLPS在体内的因果关系和功能后果更加难以捉摸。我们强调对蛋白质的内源状态和生理丰度进行定量测量的重要性，并对可能产生更结论性结果的实验​​提出建议。