Figure 3.

Shh regulates the generation of interneurons from dorsal telencephalic progenitors. E11.5 dorsolateral and dorsomedial telencephalic explants were infected with control retrovirus expressing β-gal. A, The proportion of infected cells in the dorsolateral wall that expressed GABA decreased in the presence of cyclopamine (5μm), an inhibitor of Shh signaling. Cyclopamine was added to explants for 3 d (4 div total). Explants were dissociated and cultured for 3 more days as monolayers without cyclopamine (7 div total). B, A complementary increase in glutamatergic neurons was observed when cyclopamine was added to explants. C, Blocking Shh also decreased proliferation, but did not cause a significant change in the proportion of neurons (D). Adding recombinant Shh to dorsomedial telencephalic explants for 3 d (4 div total) increased the generation of interneurons (E). Exogenous Shh reduced neuronal differentiation at 4 div (H), which might be caused by increased proliferation (G). Cells from dissociated explants were also cultured as monolayers for 3 d without Shh (7 div total). The proportion of interneurons was still greater in cultures that had been exposed to Shh (E). The proportion of neurons was not different after 7 div, but the production of glutamatergic neurons showed a complementary decrease compared to GABAergic neurons in Shh-treated cultures (F). *p = 0.04; **p ≤ 0.008; ***p = 0.0003.