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. Author manuscript; available in PMC: 2011 Jun 18.
Published in final edited form as: Brain Res. 2010 Apr 9;1338:14–19. doi: 10.1016/j.brainres.2010.04.002

Figure 2.

Figure 2

The miRNAs and the existence of molecular feedback loops. Three examples of negative feedback loops are shown for Pitx3-miR-133b, Tlx-miR-9 and Rest-miR-9. In the hypothetical model, the transcription factors (Pitx3, Tlx and REST) induce transcription of the miRNAs during neural differentiation. Those miRNAs are embedded in negative feedback circuits that normally suppress the expression of transcription factors. The proposed model also implies that miRNAs are dynamically regulated during neural differentiation (e.g. increase inexpression) and expressed regionally or specifically in some cell types (dopaminergic neurons, neural stem cells or neurons). Because transcription factors and miRNAs are co-expressed during a specific time window, the proposed function of these miRNAs is to insure the proper timing of differentiation, as opposed to a more prevalent fail-safe function in maintaining cellular homeostasis in neural cells by preventing the expression of leaky transcripts (i.e. expression buffering characterized by mutual exclusion of miRNAs and mRNA targets, not described here).