胚胎干细胞的分化既需要对自我更新进行抑制，又需要对一个特定的分化通道进行激发。被称为微RNA（miRNA）的小型非编码RNA作为支配细胞命运的重要物质正在被人们所认识。
现在研究发现，一种名为“let-7”的著名miRNA负责抑制胚胎干细胞中的自我更新程序。这种抑制可以被一组“胚胎干细胞调控型miRNA”（称之为ESCC miRNA，它们调控细胞周期）逆转，说明“let-7”和ESCC miRNA之间的互动提供一个能够支配细胞命运的机制。
生物谷推荐原始出处：
Nature 463, 621-626 (4 February 2010) | doi:10.1038/nature08725
Opposing microRNA families regulate self-renewal in mouse embryonic stem cells
Collin Melton1,2, Robert L. Judson1,2 " Robert Blelloch1,2
1 The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, Program in Biomedical Sciences,
2 Department of Urology, University of California San Francisco, San Francisco, California 94143, USA
When embryonic stem cells (ESCs) differentiate, they must both silence the ESC self-renewal program and activate new tissue-specific programs. In the absence of DGCR8 (Dgcr8 -/-), a protein required for microRNA (miRNA) biogenesis, mouse ESCs are unable to silence self-renewal. Here we show that the introduction of let-7 miRNAs―a family of miRNAs highly expressed in somatic cells―can suppress self-renewal in Dgcr8 -/- but not wild-type ESCs. Introduction of ESC cell cycle regulating (ESCC) miRNAs into the Dgcr8 -/- ESCs blocks the capacity of let-7 to suppress self-renewal. Profiling and bioinformatic analyses show that let-7 inhibits whereas ESCC miRNAs indirectly activate numerous self-renewal genes. Furthermore, inhibition of the let-7 family promotes de-differentiation of somatic cells to induced pluripotent stem cells. Together, these findings show how the ESCC and let-7 miRNAs act through common pathways to alternatively stabilize the self-renewing versus differentiated cell fates.
