Figure 8

Notch signaling in the lateral ganglionic eminence (LGE) of Gsx2;Ascl1 mutants is improved from that in Ascl1 mutants. (A) _Gsx1/2 staining in the E12.5 wild type ventral telencephalon. (B, C) Gsx1/2 staining illustrates the expansion of Gsx1 in the Gsx2 mutant LGE (B) as well as the expression of Gsx proteins in the Ascl1 mutant LGE (C); arrows point to the dorsal limit of Gsx expression. (D) Note that the Gsx1 expansion is delayed in Gsx2;Ascl1 mutants at this stage but, as shown earlier, this recovers at later stages. (E, F, H) The proneural protein Ngn2 is normally expressed in pallial progenitors (E) but in the Gsx2 (F) and Gsx2;Ascl1 mutants (H) the ventral limit of Ngn2 expression (arrows in (F, H)) has expanded ventrally into the mutant LGE. (G) In contrast, the ventral limit of Ngn2 expression in Ascl1 mutants (arrow) appears to be similar to that in wild type (E). (I-P) The status of Notch signaling can be assessed by the expression of Dll1 and Hes5. In wild types, Dll1 (I) and Hes5 (M) are expressed in ventricular zone (VZ) progenitors along the dorsal-ventral axis of the telencephalon. As is the case in the wild types, Gsx2 mutants appear to express Dll1 (J) and Hes5 (N) throughout the telencephalic VZ, while the Ascl1 mutants exhibit expression only in the dorsal telencephalon (K, O) corresponding with Ngn2 expression. Although the Gsx2;Ascl1 mutants do not show Dll1 (L) and Hes5 (P) expression in the ventral-most telencephalon (that is, medial ganglionic eminence (MGE) remnant indicated by asterisk) these Notch effectors are expressed in the mutant LGE progenitors unlike the case in Ascl1 mutants. Asterisks in (C, D, G, H, K, L, O, P) indicate the remnant of the MGE.