RESUMEN
Embryonic stem cells are the cells that have the ability both to self-renew and to differentiate into all the mature cell types in an adult. Both of these processes are tightly regulated by genetic and epigenetic mechanisms. Increasing evidence indicates that a class of single-stranded non-coding RNA, known as "microRNAs", also plays a critical role in this process. MicroRNA can bind to target mRNAs by specific base pairing, then degrade mRNAs or inhibit protein translation. Therefore, they can participate in post-transcriptional regulation. Recently, scientists began to study the effect of microRNA on embryonic stem cell and found that some microRNAs are specifically expressed and form an intricate network of microRNAs, regulating key transcription factors and other genes. This review focuses on the expression of microRNA in embryonic stem cell and their functions. We discuss some microRNA that are specifically expressed in embryonic stem cell and their regulating effect on self-renewal and differentiation.