Fig. 3. Absence of MGE progenitors in the mouse Shh^N/- telencephalon. (A-D) Nkx2.1 expression in control (A), Shh^N/- (B), Shh^flox/- (C) and Shh^-/- (D) telencephalons. Nkx2.1 is an MGE marker (arrow in A points to the boundary of the Nkx2.1 expression domain) and its expression is maintained in Shh^flox/-, but lost in Shh^N/- and Shh^-/-, telencephalons. (E-H) Mash1 expression in control (E), Shh^N/- (F), Shh^flox/- (G) and Shh^-/- (H) telencephalons. Mash1 expression delineates the ventral region of the control telencephalon, encompassing the MGE and LGE. Mash1 expression was reduced in the LGE domain of Shh^flox/- as compared with the control. Mash1 expression was maintained in the ventral Shh^N/- telencephalon (arrows in E and F point to the boundary of the Mash1 expression domain). No Mash1-positive cells were found in Shh^-/- telencephalon at this stage. (I-L) Pax6 expression in the telencephalon of control (I), Shh^N/- (J) Shh^flox/- (K) and Shh^-/- (L) embryos. Pax6 normally marks the dorsal telencephalon with the exception of the distal dorsal midline. Note that weak Pax6 expression extends to the ventral region in the Shh^N/- telencephalon (arrows in I and J point to the presumptive boundary between neocortex and LGE). Shh^flox/- showed comparable Pax6 expression to that of the control, whereas the Shh^-/- telencephalon was completely dorsalized at this stage. Brackets indicate LGE domains. ncx, neocortex; MGE, medial ganglionic eminence; LGE, lateral ganglionic eminence.