Dani C, Chambers I, Johnstone S, Robertson M, Ebrahimi B, Saito M, Taga T, Li M, Burdon T, Nichols J, Smith A
Centre for Genome Research, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JQ, Scotland.
Dev Biol. 1998 Nov 1;203(1):149-62. doi: 10.1006/dbio.1998.9026.
The propagation of pluripotential mouse embryonic stem (ES) cells is sustained by leukemia inhibitory factor (LIF) or related cytokines that act through a common receptor complex comprising the LIF receptor subunit (LIF-R) and the signal transducer gp130. However, the findings that embryos lacking LIF-R or gp130 can develop beyond gastrulation argue for the existence of an alternative pathway(s) governing the maintenance of pluripotency in vivo. In order to define those factors that contribute to self-renewal in ES cell cultures, we have generated ES cells in which both copies of the lif gene are deleted. These cells showed a significantly reduced capacity for regeneration of stem cell colonies when induced to differentiate, confirming that LIF is the major endogenous regulatory cytokine in ES cell cultures. However, self-renewal was not abolished and undifferentiated ES cell colonies were still obtained in the complete absence of LIF. A differentiated, LIF-deficient, parietal endoderm-like cell line was derived and shown to support ES cell propagation via production of a soluble, macromolecular, trypsin-sensitive activity. This activity, which we name ES cell renewal factor (ESRF), is distinct from members of the IL-6/LIF family because (i) it is effective on ES cells lacking LIF-R; (ii) it is not blocked by anti-gp130 neutralizing antibodies; and (iii) it acts without activation of STAT3. ES cells propagated clonally using ESRF alone can contribute fully to chimaeras and engender germline transmission. These findings establish that ES cell pluripotency can be sustained via a LIF-R/gp130-independent, STAT-3 independent, signaling pathway. Operation of this pathway in vivo could play an important role in the regulation of pluripotency in the epiblast and account for the viability of lifr -/- and gp130 -/- embryos.
多能性小鼠胚胎干细胞（ES细胞）的增殖由白血病抑制因子（LIF）或相关细胞因子维持，这些因子通过一个共同的受体复合物发挥作用，该复合物由LIF受体亚基（LIF-R）和信号转导子gp130组成。然而，缺乏LIF-R或gp130的胚胎能够发育至原肠胚形成期之后，这一发现表明体内存在另一条调控多能性维持的途径。为了确定那些有助于ES细胞培养中自我更新的因子，我们构建了lif基因两个拷贝均被缺失的ES细胞。当诱导分化时这些细胞显示出干细胞集落再生能力显著降低，证实LIF是ES细胞培养中的主要内源性调节细胞因子。然而，自我更新并未被消除，在完全没有LIF的情况下仍能获得未分化的ES细胞集落。一种分化的、缺乏LIF的、壁内胚层样细胞系被分离出来，并显示其通过产生一种可溶性的、大分子的、对胰蛋白酶敏感的活性物质来支持ES细胞增殖。这种活性物质，我们命名为ES细胞更新因子（ESRF），不同于IL-6/LIF家族成员，因为（i）它对缺乏LIF-R的ES细胞有效；（ii）它不被抗gp130中和抗体阻断；（iii）它在不激活STAT3的情况下发挥作用。仅使用ESRF进行克隆培养的ES细胞能够完全参与嵌合体形成并实现种系传递。这些发现表明ES细胞多能性可以通过一条不依赖LIF-R/gp130、不依赖STAT-3的信号通路得以维持。该通路在体内的运作可能在调控上胚层多能性方面发挥重要作用，并解释了lifr -/-和gp130 -/-胚胎的存活情况。
