Fig. 1.
Changes in Six3 levels lead to different types of HPE-like phenotypes in mice. Scanning electron microscopy analysis was performed on E10.5 wild-type (A), Six3neo/neo (E) and Six3neo/– (I) embryos. The telencephalic vesicles are pseudocolored in magenta, medial nasal prominences (MNPs) in yellow, and lateral nasal prominences (LNPs) in green. (A) In control embryos, both the telencephalic vesicles and the MNPs are well separated (n=3). (E) In Six3neo/neo embryos, the LNPs are well formed; however, a single telencephalic vesicle is present and the MNP is not separated (n=2). (I) In Six3neo/– embryos, the single telencephalic vesicle is small, the MNPs are absent and the LNPs are not separated (n=2). Coronal sections [rostral (R) to caudal (C)] of P0 control (B-D), Six3neo/neo (F-H) and Six3neo/– (J-L) pups stained with Hematoxylin and Eosin. At the most rostral level, the cartilage nasal septum is seen in controls (B, arrow), but this structure is severely defective in Six3neo/neo pups (F, arrow). The nasal structures are absent in Six3neo/– pups (J, arrow). At the mid level, the corpus callosum (C,G,K, red arrows) and the septum (C,G,K, black arrows) are absent in Six3neo/neo and Six3neo/– embryos. More caudally, the cerebral hemispheres are well formed and separated by the diencephalon and the hippocampus in wild-type and in Six3neo/neo pups (D,H, arrows). However, the hippocampus is relatively enlarged and misplaced on the surface of the brain (L, arrow). n=3 control; n=4 Six3neo/neo; n=3 Six3neo/−.