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. Author manuscript; available in PMC: 2009 Jan 1.
Published in final edited form as: Crit Rev Oncol Hematol. 2007 Jul 23;65(1):43–53. doi: 10.1016/j.critrevonc.2007.06.004

Fig. 3.

Fig. 3

A model for miRNA action in neural stem cells. Molecules that are expressed in neural stem cells to maintain their self-renewable state are collectively referred to as stem cell maintenance factors. miRNAs are initially transcripted in the nucleus as pri-miRNAs. The pri-miRNAs are processed into pre-miRNAs (hairpin) and transferred to the cytosol, where it is processed into 22-24 nucleotide mature miRNAs. Upon differentiation, miRNAs, such as miR-124 and miR-128, are highly expressed in the neuronal lineage, whereas miR-23, miR-26, and miR-29 are upregulated in glia. MiR-9 and miR-125 are expressed in both neurons and glia. These miRNAs form incomplete base paring with their target mRNAs and direct the cleavage of these mRNAs or inhibit their translation, thus preventing the expression of the stem cell maintenance factors and enabling rapid neural differentiation.