Figure 7.
Electroporation of cell-specific promoters was used to differentially label short and long VZ cells. A–E, The Tα1 promoter construct preferentially labels short VZ cells (supplemental movie 5, available at www.jneurosci.org as supplemental material). A, Forty-eight hours after in utero electroporation with pTα1-hGFP, many neurons generated from the VZ and SVZ are found migrating radially through the IZ into the CP. B, At higher magnification, very few GFP+ ascending fibers from RGCs were found in superficial portions of the neocortical wall. C, Most neurons migrating into the CP appeared bipolar, with thin trailing processes and longer, thicker leading processes, and did not appear to be associated with GFP+ RGC fibers. D, E, Reconstructed VZ cells (arrowheads), depicted here in collapsed stacks within which they were fully contained, had short ascending processes (double arrowheads) before their entry into metaphase (D), and lacked processes when dividing at the surface of the ventricle (E). 3D-reconstructed mitotic cells were scored as short (black bars) or long cells (white bars) 24 h (F) or 48 h (G) after in utero electroporation with pGlast-EGFP, pBlbp-EGFP, or pTα1-hGFP. Of the total number of cells expressing each construct, pGlast-EGFP and pBlbp-EGFP were primarily expressed by long RGCs. Conversely, short dividing cells preferentially expressed the pTα1-hGFP construct. The percentage of unclassifiable cells is represented as N.D.(> 18,000 transfected cells were scored for the experiments in F and G). H, Cotransfection of EGFP/DsRed2 plasmid pairs demonstrated that mitotic VZ cells expressing either pGlast or pBlbp did not concurrently express pTα1, although long cells did coexpress pGlast and pBlbp. *p < 0.0001. Error bars indicate SE.