Figure 3.
Cell-type specificity of Cre expression in POMC-Cre transgenic mice. a1–a4, Immunohistochemistry of hippocampal sections from POMC-Cre mice at P15, labeled using antibodies for Cre (red) and a neuron specific marker, NeuN (green). NeuN-positive granular neurons (a1; green) and Cre-positive newborn neurons (a2; red) are located in the postnatal dentate gyrus. In a3, the merged image of a1 and a2 shows that Cre-positive cells are located in the inner granular layer and are adjacent to NeuN-positive mature granular neurons. a4 is an amplified view of a3 of Cre (red) and NeuN (green) double staining to show that Cre is not expressed in NeuN positive cells. b1–b4, Immunohistochemistry of hippocampal sections using antibodies for Dcx (green), a marker of migrating newborn neurons, and Cre (red). The Dcx-positive neurons (b1; green) are located in the same layer as Cre positive cells (b2; red). The merged image (b3) and the enlarged view (b4) of these pictures show that Cre is highly expressed in Dcx-positive newborn neurons in the dentate gyrus. c1–c4, Immunofluorescence labeling for Nestin (green), a marker of neural progenitor cells, and Cre (red). The Nestin-positive cell bodies (green; b1, b3, and b4) are located below the Cre-positive cell layer (red; c2, c3, and c4). The enlarged view (c4) of the merged image (c3) shows that the Nestin is highly expressed in the processes of neural progenitors, but is very weakly expressed in the cell bodies. We do not see any colocalization of Nestin signals and Cre signals. These results suggest that Cre is specifically expressed in the Dcx positive-newborn neurons in the postnatal dentate gyrus. Scale bars: a3, b3, c3, 100 μm; a4, b4, c4, 20 μm.