Extended Data Fig. 9: At 22 GW, the CGE contains Ki-67⁺SOX2⁺ progenitors and many SP8⁺, COUPTFII⁺ and PROX1⁺ cells.

a, Diagrams of coronal sections of one hemisphere of the human brain at 22 GW at one anterior and one posterior level of the CGE. Red boxes indicate inset locations of immunostaining for Ki-67⁺SOX2⁺ cells. Immature DCX⁺ neurons are present in clusters between the Ki-67⁺SOX2⁺ cells (i-vi). In the ventral V-SVZ, fewer Ki-67⁺SOX2⁺ cells are visible (vii-ix). b, Diagrams of coronal sections at three cross-sections across the temporal lobe and immunostains for SP8, COUPTFII, and PROX1 at each level showing that each marker is highly expressed throughout the CGE. c, Ultrastructure of a migratory young neuron at 22 GW in the temporal lobe CGE. This cell has a classical localization of the Golgi (green arrow) and centrosome (magenta arrowhead) in the leading process filled with microtubules and displays an adherens junction (magenta arrow). Immunogold labelling for DCX reveals processes filled with microtubules at this age. d, Immunostaining of the 22-GW human temporal lobe at the level of the anterior hippocampus. Insets show higher magnification of SCGN+ cells densely clustered near the ventral extension of the temporal lobe lateral ventricle and extending into the EC. Scale bars: 2 mm (a maps, b all panels), 500 µm (a left immunostaining overviews, d), 100 µm (d inset), 20 µm (a right panels i-ix), 1 µm (c top left), 200 nm (c top right, bottom panels). Abbreviations: BLA: basolateral amygdala; CGE: caudal ganglionic eminence; EC: entorhinal cortex; HP: hippocampus; oSVZ: outer subventricular zone; tLV temporal lobe lateral ventricle; V-SVZ: ventricular–subventricular zone.