Fig. 6. Complementary Id2 and Cdh6 expression domains show a molecular shift in the orbitofrontal and frontal neocortex of Fgf8neo/neo newborns. Id2 (A-H) and Cdh6 (A'-H') in situ hybridization were performed on adjacent 100 µm sections (A-H and A'-H') from the rostral brain of a wild-type (A-D') and a Fgf8neo/neo (E-H') newborn. In wild type, Id2 and Cdh6 expression delimit two complementary zones (black arrowheads in A-D'): a rostral and medial domain of high Id2^rs, low Id2⁵ and low Cdh6 expression, and a lateral parietal domain of low Id2^rs, high Id2⁵ and Cdh6 expression. These two zones are still observed in Fgf8neo/neo newborns (black arrowheads in E-H'). However the rostral and medial domain is severely reduced and the lateral parietal domain expands both medially and rostrally (E-H'), even into the rostralmost neocortex (E,E'). 5, layer 5 expression; Ncx, neocortex; rs, rostral superficial expression; OB, olfactory bulb.