The TCA-TLZ reporter line reveals the TCA pathfinding and cortical lamination defects of the reeler mutant. (A, A') In a P0 control brain, the TCAs elongate (dark blue) in the subplate (sp) layer beneath the cortical plate, and extend collateral branches (br, lighter blue) up to layer 4. (B, B') In the reeler mutant brain, the cortex is roughly inverted (ctx*), the subplate is abnormally positioned (sp*) at the top of cortex, and the TCA fascicles can be seen crossing the cortical plate to reach it. Dotted lines indicate top of cortical plate at cut edge of hemisphere. dTh, dorsal thalamus.