A subventricular zone exists in the embryonic mouse thalamus. (A-H') Confocal images of frontal sections of E11.5 (A-D,C',D') and E12.5 (E-H,G',H') mouse forebrain showing combined immunostaining of NICD (intracellular domain of Notch1) or Pax6 with 0.5-hour pulse-labeled ethynyl deoxyuridine (EdU). Midline is to the left. Panels (C) and (C'), (D) and (D'), (G) and (G') as well as (H) and (H') are from the same section, respectively. Dashed lines in (A,C,C',E,G,G') show the lateral border of NICD-expressing cells, and dashed lines in (D,D',H,H') show the lateral border of cells with strong Pax6 expression. Solid lines in (C',G') show the lateral border of EdU-expressing cells. The space between the dashed line and the solid line in (C',G') represents the thalamic subventricular zone (SVZ). PH3-positive cells shown by arrowheads (A,B,E,F) indicate dividing cells within the VZ, whereas those shown by arrows (A,B,E,F,D',H') are located outside the VZ within the SVZ. Scale bar: 100 μm. 3V, third ventricle; SVZ, subventricular zone; VZ, ventricular zone.