Figure 6.

Robo/Dll1 Signaling Regulates the Balance between Direct Neurogenesis and IPC Abundance in Chick Dorsal Pallium

(A–D) Analysis of chick dorsal pallium at 6 days post-ovoposition (dpo), showing many neurons in the VZ (solid arrowheads) in the medial part (mDP; B) and basal mitoses (open arrowheads) in the lateral (lDP; C; n = 3 embryos; t tests).

(E–H) ISH in chick DP at 6 dpo, and quantifications of intensity (au, arbitrary units). High magnifications show chkRobo1 (E’ and E”) and chkDll1 (G’ and G”) in the indicated regions. Panel shown in (G) is a tiled image.

(I) qPCR analysis in the VZ of the regions and species indicated. Values are ratio Robo1 to Gapdh (n = 12–15 replicates; paired or independent samples t tests).

(J–O) Experimental design to manipulate in ovo Robo and Dll1 in mDP and lDP, representative examples and quantifications of neurons in the VZ (Tbr1+) and basal mitoses (PH3, open arrowheads; n = 3-5 embryos per group; t tests in L and Q; one-way ANOVA followed by t tests in M and O). Red shadowing and asterisks in (L) and (O) indicate values within group corresponding to GFP− cells.

(P and Q) Expression of Tbr2 in basal PH3+ mitoses (solid arrowhead, Tbr2+; open arrowhead, Tbr2−) upon electroporation of dnR1/2+Dll1 in mDP (as in J and K), and quantification (n = 4–5 embryos; t tests).

(R–U) Analysis of neuronal clones (GFP+RFP+Tuj1+) upon overexpression of dnR1/2+Dll1+Gfp, representative examples and quantification (n = 52 clones Gfp, 59 clones dnR1/2+Dll1+Gfp, 3–7 embryos; t test or χ2-test).

Values are mean + SEM; ^∗p < 0.05; ^∗∗p < 0.01; ^∗∗∗p < 0.001. Scale bars: 100 μm (A, E, F, and G), 50 μm (B, C, K, N, P, and S).