【原】MTORC1必要且充分控制静止干细胞从G0到G（alert）的适应性转变

mTORC1 controls the adaptive transition of quiescent stem cells from G0 to G(Alert).

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|核心内容：

许多成体干细胞的一个独特特性是它们能够在无细胞周期、静止状态下生存。

尽管静止状态在维持干细胞功能方面起着至关重要的作用，直到组织内稳态或修复需要干细胞，但静止状态的缺陷可能会导致组织功能受损。（静息状态细胞变少还是处于静息状态的细胞本身有问题？）

干细胞能在多大程度上调节静止尚不清楚。

在这里，我们展示了干细胞静止状态由两个不同的功能阶段组成，G0和一个我们称之为G(警报)的“警报”阶段。

干细胞在这些阶段之间积极且可逆地转换，以响应损伤诱导的系统信号。

利用特定于肌肉干细胞(或卫星细胞)的小鼠遗传模型，我们证明了mTORC1活性对于卫星细胞从G0到G(Alert)的转变是必要和充分（单独激活mTORC1即可，无需去除其他信号通路）的，并且通过HGF受体cMET发出的信号也是必要的。

我们还在几个静止干细胞群体中发现了从G0到G(Alert)的转变。

转化为G(Alert)的静止干细胞具有增强的组织再生功能。

我们认为，静止干细胞向G(Alert)的转变是一种“警示”机制，是一种适应性反应，使干细胞在损伤和应激条件下迅速做出反应，为细胞周期进入做好准备。

#mTORC1的活性与营养，生长因子相对应。其激活对于组织的损伤修复非常重要，所以长身体或者需要组织进行损伤修复的时候多补充营养。平时七分饱即可。

原文摘要：

A unique property of many adult stem cells is their ability to exist in a non-cycling, quiescent state. 

Although quiescence serves an essential role in preserving stem cell function until the stem cell is needed in tissue homeostasis or repair, defects in quiescence can lead to an impairment in tissue function. （what logic？)

The extent to which stem cells can regulate quiescence is unknown. Here we show that the stem cell quiescent state is composed of two distinct functional phases, G0 and an 'alert' phase we term G(Alert). 

Stem cells actively and reversibly transition between these phases in response to injury-induced systemic signals. 

Using genetic mouse models specific to muscle stem cells (or satellite cells), we show that mTORC1 activity is necessary and sufficient for the transition of satellite cells from G0 into G(Alert) and that signalling through the HGF receptor cMet is also necessary. 

We also identify G0-to-G(Alert) transitions in several populations of quiescent stem cells. Quiescent stem cells that transition into G(Alert) possess enhanced tissue regenerative function.

We propose that the transition of quiescent stem cells into G(Alert) functions as an 'alerting' mechanism, an adaptive response that positions stem cells to respond rapidly under conditions of injury and stress, priming them for cell cycle entry.

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参考文献：mTORC1 controls the adaptive transition of quiescent stem cells from G0 to G(Alert).

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