Pitx2 Expression Promotes p21 Expression and Cell Cycle Exit in Neural Stem Cells
Pitx2 Expression Promotes p21 Expression and Cell Cycle Exit in Neural Stem Cells
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DOI：
10.2174/1871527311201070884
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发表时间：
2012-11-01
影响因子：
3
通讯作者：
Kioussi, Chrissa
中科院分区：
文献类型：
--
作者：
Heldring, Nina;Joseph, Bertrand;Kioussi, Chrissa
皮质发育是一个复杂的过程，涉及许多事件，包括增殖，细胞周期退出和分化，需要适当同步。神经干细胞（NSCs）是从胚胎皮层中分离出来的，具有自我更新的能力，并能持续保持多能性。发育过程中的细胞周期进程和停滞受许多因素调节，包括细胞周期蛋白、细胞周期蛋白依赖性激酶及其抑制剂。在这项研究中，我们外源性表达的同源结构域转录因子Pitx 2，通常在有丝分裂后的祖细胞和神经元的胚胎皮层，在神经干细胞与内源性Pitx 2低表达。我们发现Pitx 2表达诱导了与G1期神经干细胞积累相关的增殖迅速下降。对负责NSC的这种细胞周期退出的潜在细胞周期抑制剂的搜索显示，Pitx 2表达引起细胞周期抑制剂p21（WAF 1/Cip 1）表达的快速和显著（约20倍）增加。此外，Pitx 2直接结合p21启动子，如通过染色质免疫沉淀（ChIP）在神经干细胞中所评估的。令人惊讶的是，Pitx 2表达与分化标志物的增加无关，而是与未分化的NSC相关的巢蛋白表达得以维持。我们的研究结果表明，Pitx 2促进p21的表达，并诱导神经祖细胞的细胞周期退出。
Cortical development is a complex process that involves many events including proliferation, cell cycle exit and differentiation that need to be appropriately synchronized. Neural stem cells (NSCs) isolated from embryonic cortex are characterized by their ability of self-renewal under continued maintenance of multipotency. Cell cycle progression and arrest during development is regulated by numerous factors, including cyclins, cyclin dependent kinases and their inhibitors. In this study, we exogenously expressed the homeodomain transcription factor Pitx2, usually expressed in postmitotic progenitors and neurons of the embryonic cortex, in NSCs with low expression of endogenous Pitx2. We found that Pitx2 expression induced a rapid decrease in proliferation associated with an accumulation of NSCs in G1 phase. A search for potential cell cycle inhibitors responsible for such cell cycle exit of NSCs revealed that Pitx2 expression caused a rapid and dramatic (approximate to 20-fold) increase in expression of the cell cycle inhibitor p21 (WAF1/Cip1). In addition, Pitx2 bound directly to the p21 promoter as assessed by chromatin immunoprecipitation (ChIP) in NSCs. Surprisingly, Pitx2 expression was not associated with an increase in differentiation markers, but instead the expression of nestin, associated with undifferentiated NSCs, was maintained. Our results suggest that Pitx2 promotes p21 expression and induces cell cycle exit in neural progenitors.