Figure 4

Removal of Ascl1 on the Gsx2 mutant background exacerbates the Gsx2 mutant phenotype in the striatum. (A) FoxP1 expression labels striatal projection neurons at E18.5. (B) In Gsx2 mutants, the expression domain of FoxP1 in the striatum is severely reduced. (D) Removal of Ascl1 on the Gsx2 mutant background (Gsx2;Ascl1 double mutant) results in a more severe effect on the FoxP1 expression domain compared to Gsx2 mutants (compare (D) to (B)). (C) Ascl1 mutants display relatively normal expression of FoxP1 in the striatum. (E-G) Gsx2 mutants also exhibit a severe reduction in DARPP-32 expression (F), which is enriched in early born striatal neurons at E18.5 in controls (E) and Ascl1 mutants (G). (H) Gsx2;Ascl1 double mutants display a more severe phenotype in DARPP-32 expression compared to Gsx2 mutants (compare (H) to (F)). Note that Gsx2;Ascl1 double mutants display a complete loss of DARPP-32 positive neurons in the striatum (H). The only DARPP-32 staining observed in the double mutant striatum is in fibers (arrow in (H)), which presumably arise from the cortical DARPP-32 expressing neurons. (I, J, L) Calbindin (CB) expression labels the later born striatal neurons at E18.5 (I) and is upregulated in the SVZ of Gsx2 mutants (J) and Gsx2;Ascl1 double mutants (L). (K) Ascl1 mutants exhibit a noticeable reduction in CB expression in the striatum. ac, anterior commissure.