Figure 4.
Exogenous expression of Kir2.1 in layer 2/3 cortical neurons does not affect their neuronal identity, migration, or axonal extension. A, Immunostaining using anti-NeuN antibody (red) showed that Kir2.1-transfected neurons (GFP-labeled cell bodies in the right) resided in the correct cortical layer. GFP electroporation was performed at E15.5; images from P15 cortical sections. Scale bar, 200 μm. B, Immunostaining using anti-Brn-1 antibody (red) showed that Kir2.1-transfected neurons expressed the transcription factor Brn-1. Brn-1 is involved in neuronal identity specification. Arrows in the insets indicate GFP-labeled cell bodies expressing Brn-1. Scale bar, 50 μm. C, Numerous GFP-labeled axons expressing Kir2.1 crossed the midline and projected to the contralateral cortex in a fasciculated tract at P5. Scale bar, 500 μm. D, GFP-labeled axons reached the 17/18 border by P5 (left). There was no apparent developmental delay in the arrival of axons expressing Kir2.1 (right). Arrows indicate callosal axon fibers. Arrowheads indicate the border between areas 17 and 18. In the bottom panels, DAPI staining was used to show cortical layers. Hp, Hippocampus; Cx, cerebral cortex. Scale bars: top, 500 μm; bottom, 200 μm.