Figure 3. The differential expression of members of the Gli/Ci family of transcription factors controls the response of progenitors to Shh in the ventral telencephalon at distinct embryonic ages.
(top panel) The distribution of Gli protein expression within the telencephalon at E9.5 [72] and (middle and bottom panels) E12.5 in patterns dictates the differential responses of progenitors to Shh. At E12.5, the targets of Shh-signaling Nkx6-2 (blue) and Gli1 (green) can be observed only in the Gli2-expressing domains (purple) that are closest to the ventral sources of Shh (red) along the rostro-caudal axis of the telencephalon. Gli3 (brown) is expressed in a dorsal-to-ventral gradient in the entire telencephalon with a characteristic low level of expression in the MGE (that is apparently insufficient to provide enough Gli-activator function to allow for expression of Nkx6-2 or Gli1).