The microRNA-processing enzyme Dicer is dispensable for somite segmentation but essential for limb bud positioning

► Dicer is essential for paraxial mesodermal cell survival. ► Dicer is essential for establishing rostral-caudal polarity of somites. ► Paraxial mesoderm segmentation occurs in the absence of Dicer. ► Dicer is essential for limb bud positioning. ► Dicer may act via miRNAs to control Hand2/Tbx3 expression and limb positioning.