Summary of miR-223 regulation and function. miR-223 expression rises incrementally during successive stages of granulocytic differentiation. At the transcriptional level, miR-223 is induced by myeloid-specific factors, such as PU.1 and C/EBPβ, and inhibited by NFI-1. miR-223 inhibits Mef2c and NFI-1, the latter forming a positive feedback circuit.