Miyabayashi Tomoyuki, Teo Jia-Ling, Yamamoto Masashi, McMillan Michael, Nguyen Cu, Kahn Michael
Central R&D Laboratories, Asahi Kasei Corporation, Shizuoka 416-8501, Japan.
Proc Natl Acad Sci U S A. 2007 Mar 27;104(13):5668-73. doi: 10.1073/pnas.0701331104. Epub 2007 Mar 19.
Embryonic stem cells (ESCs) represent an important research tool and a potential resource for regenerative medicine. Generally, ESCs are cocultured with a supportive feeder cell layer of murine embryonic fibroblasts, which maintain the ESCs' capacity for self-renewal and block spontaneous differentiation. These cumbersome conditions, as well as the risk of xenobiotic contamination of human ESCs grown on murine embryonic fibroblasts, make it a priority to develop chemically defined methods that can be safely used for the expansion of ESCs. Using a high-throughput, cell-based assay, we identified the small molecule IQ-1 that allows for the Wnt/beta-catenin-driven long-term expansion of mouse ESCs and prevents spontaneous differentiation. We demonstrate that IQ-1, by targeting the PR72/130 subunit of the serine/threonine phosphatase PP2A, prevents beta-catenin from switching coactivator usage from CBP to p300. The increase in beta-catenin/CBP-mediated transcription at the expense of beta-catenin/p300-mediated transcription is critical for the maintenance of murine stem cell pluripotency.
胚胎干细胞（ESCs）是再生医学的重要研究工具和潜在资源。一般来说，胚胎干细胞与小鼠胚胎成纤维细胞的支持性饲养层共培养，后者维持胚胎干细胞的自我更新能力并阻止其自发分化。这些繁琐的条件，以及在小鼠胚胎成纤维细胞上生长的人类胚胎干细胞受到异种生物污染的风险，使得开发能够安全用于胚胎干细胞扩增的化学成分明确的方法成为当务之急。通过基于细胞的高通量分析，我们鉴定出小分子IQ-1，它能实现Wnt/β-连环蛋白驱动的小鼠胚胎干细胞长期扩增并防止自发分化。我们证明，IQ-1通过靶向丝氨酸/苏氨酸磷酸酶PP2A的PR72/130亚基，阻止β-连环蛋白将共激活因子的使用从CBP切换为p300。以β-连环蛋白/p300介导的转录为代价，β-连环蛋白/CBP介导的转录增加对于维持小鼠干细胞多能性至关重要。
