Subcellular localization of Annexin A7 in embryos E13, E15 and E16. Paraffin sections of embryonic brain were stained with purified mAb 203–217. Annexin A7 was visualized with Alexa Fluor 488-conjugated secondary antibody. (A) Overview, at E16 the immature GFAP-negative cells of the forming cerebral neocortex (b) surrounding the lateral ventricle (a) are strongly stained; square, a higher magnification of this area is given in (I). (B) Higher magnification of the earlier stage E13 (H) shows, that the cells are stained in the cytosol (arrowhead). (C) Two days later at E15 the cells have rounded up, and Annexin A7 stays in the cytosol. (D) At E16 the first nuclear staining becomes apparent (arrowhead) in cells of the intermediate zone located between ventricular germinative zone and marginal neopallial cortex as seen in (I), oval. (E-G) Confocal microscopy confirms the results in B-D. (H) Overview, at E13 the immature GFAP-negative cells are strongly stained; a, lateral ventricle. (I) Higher magnification of a cortical section of (A, square) demonstrating ventricular, intermediate, and marginal zones; oval, a higher magnification of this area is given in (D,G).