Immunohistochemistry was carried out as previously described28,51. Antibodies included: mouse anti-NeuN (1:1000; MAB377, Millipore Corporation), rabbit anti-BAF53b (1:500; generous gift from G.R. Crabtree), goat anti-mouse IgG–FITC secondary antibody (1:1000; Millipore Bioscience Research Reagents), and donkey anti-rabbit IgG-CY3 (1:1000; Jackson ImmunoResearch).
