Immunohistochemical detection of β-galactosidase expression in the brain of endoxifen-injected GLAST::CreERT2;ROSA26loxP/loxP or in Adeno-Cre-injected ROSA26loxP/loxP reporter mice. Left column: expression of β-galactosidase in clusters of cells in the SVZ of the lateral ventricles (A,D), and in ependymal cells (G) of the third ventricle. Arrowhead in A points to a recombined cluster of cells. Cells of the choroid plexus (J) are not recombined: they do not express GLAST in this mouse. Insert in G shows recombined cells in the ependymal layer. Middle column: upon Adeno-Cre-mediated recombination, there is widespread expression of β-galactosidase in the cells of the SVZ (B,E), and ependymal cells of the third ventricle (H). Also, a population of choroid plexus cells (K) underwent recombination and expressed β-galactosidase. Right column: no recombination is seen in controls, which were injected with PBS. (M-O) Widespread expression in the brain is seen after intraperitoneal application of tamoxifen, including in astrocytes in the cortex (N; higher-magnification view of the uppermost box in M) and deep beneath the SVZ (O; higher-magnification view of the lowermost box in M). Scale bar: 50 µm (A-C,N,O), 100 µm (D-L), 1.8 mm (M).