Embryonic GFAP+ cells mainly produce neurons in the cortex of the young adult mouse. X-gal+ cells were identified using double immunohistochemical staining with antibodies for BLBP (A, C) and NeuN (B, D). Most X-gal+ cells co-expressed NeuN (B, D), and only a few were stained with BLBP (A, C) in both the superficial and deep cortex of the dorsal forebrain. Scale bars, 10 μm in A–D; 5 μm in insets.