AKT signaling promotes derivation of embryonic germ cells from primordial germ cells
AKT signaling promotes derivation of embryonic germ cells from primordial germ cells
复制标题
DOI：
10.1242/dev.013474
复制
发表时间：
2008-03-01
期刊：
影响因子：
4.6
通讯作者：
Nakano, Toru
中科院分区：
文献类型：
--
作者：
Kimura, Tohru;Tomooka, Maya;Nakano, Toru
原始生殖细胞（PGCs）是胚胎生殖细胞的前体。虽然PGCs的发育潜能仅限于生殖谱系，但PGCs可以获得多能性，如通过体外建立胚胎生殖（EG）细胞和体内产生睾丸畸胎瘤所证实的。PGC特异性失活的PTEN，这是一种脂质磷酸酶拮抗磷酸肌醇-3激酶（PI 3 K），增强EG细胞的生产和睾丸畸胎瘤的形成。在这里，我们分析了丝氨酸/苏氨酸激酶AKT，PI 3 K的主要下游效应之一，对PGCs的发育潜能的影响。我们使用表达AKT-MER融合蛋白的转基因小鼠，其激酶活性可由修饰的雌激素受体（MER）的配体4-羟基他莫昔芬调节。我们发现在增殖期PGCs中AKT信号的过度激活显著增强了EG细胞建立的效率。此外，AKT信号转导激活在一定程度上取代了bFGF的作用，bFGF是EG细胞建立的必需生长因子。相比之下，AKT激活对有丝分裂停滞或在胚胎后期开始减数分裂的生殖细胞没有影响。在转基因PGCs中，AKT激活诱导GSK 3磷酸化，这抑制了其激酶活性;增强了MDM 2的稳定性和核定位;并抑制了其激活所需的p53磷酸化。p53缺陷，而不是GSK 3抑制，概括了AKT超活化对EG细胞衍生的影响，表明p53是PI 3 K/AKT信号的关键下游靶点之一，而GSK 3不是。
Primordial germ cells (PGCs) are embryonic germ cell precursors. Although the developmental potency of PGCs is restricted to the germ lineage, PGCs can acquire pluripotency, as verified by the in vitro establishment of embryonic germ (EG) cells and the in vivo production of testicular teratomas. PGC-specific inactivation of PTEN, which is a lipid phosphatase antagonizing phosphoinositide-3 kinase (PI3K), enhances both EG cell production and testicular teratoma formation. Here, we analyzed the effect of the serine/threonine kinase AKT, one of the major downstream effectors of PI3K, on the developmental potency of PGCs. We used transgenic mice that expressed an AKT-MER fusion protein, the kinase activity of which could be regulated by the ligand of modified estrogen receptor (MER), 4-hydroxytamoxifen. We found that hyperactivation of AKT signaling in PGCs at the proliferative phase dramatically augmented the efficiency of EG cell establishment. Furthermore, AKT signaling activation substituted to some extent for the effects of bFGF, an essential growth factor for EG cell establishment. By contrast, AKT activation had no effect on germ cells that were in mitotic arrest or that began meiosis at a later embryonic stage. In the transgenic PGCs, AKT activation induced phosphorylation of GSK3, which inhibits its kinase activity; enhanced the stability and nuclear localization of MDM2; and suppressed p53 phosphorylation, which is required for its activation. The p53 deficiency, but not GSK3 inhibition, recapitulated the effects of AKT hyperactivation on EG cell derivation, suggesting that p53 is one of the crucial downstream targets of the PI3K/AKT signal and that GSK3 is not.