Fig. 5. Exogenous Shh rescues Nkx2.1 expression and somatostatin fate of NsCre:Shh^Fl/Fl MGE progenitors in vitro. (A,B) Sections (12 µm) from slices cultured from E13.5 NsCre:Shh^Fl/Fl + 1 DIV. BrdU was added to the culture medium 6 hours before fixation. Control sections (A) show a marked reduction of Nkx2.1 in the MGE, primarily in the proliferative region. When cultured with 10 nM Shh (B), Nkx2.1 expression is rescued in the proliferative region of the MGE. (C) Quantification of similarly treated sections co-labeled for Nkx2.1 and BrdU. Although the addition of Shh does not affect the overall percentage of BrdU+ cells (left), the percentage of these cells that co-express Nkx2.1 is increased nearly 3-fold (right). To determine the fate potential of the BrdU-labeled cells, the proliferative region of the MGE was transplanted onto cortical feeders and immunolabeled for BrdU and somatostatin (D). (E) Quantification of the percentage of BrdU⁺ cells that co-labeled with Som, showing a marked reduction in NsCre:Shh^Fl/Fl compared with wild type, and a partial restoration of Som-BrdU co-labeling following the addition of Shh (n=3). Scale bar in D: 200 µm.