Annu. Rev. Cell Dev. Biol. 2007.23:175-205

Mutually exclusive expression of miRNAs and their targets. (a) miRNAs and their targets can be

expressed in a temporally reciprocal manner: Target transcription may be turned off, concurrent with the turning on of miRNA expression. miRNA expression may also actively contribute to target repression, without an underlying change in target transcription. (b) In the case of spatial reciprocity, the miRNA  and its targets, e.g., miR-124 ( green) and its target repo (red ) in the Drosophila central nervous system, are often expressed in adjacent domains (from Stark et al. 2005).