(A), Dorsal view of the skull vault of an E18.5 Mef2c-F10N-Cre;R26R embryo stained with X-gal. (B–D) Skull double stained for X-gal and Alizarin red in dorsal (B) and lateral (C, D) views. (D), Higher magnification image of specimen in (C). (E, F) Frontal sections through the forebrain region of an E14.5 embryo corresponding to inset in Fig.7B. Distribution of β-galactosidase activity revealed by bright field microscopy and also by direct detection of far-red (633nm) X-gal fluorescence in conjunction with immunostaining for neural maturation, (Tuj1) and nuclei, (DAPI). Red arrowheads in (A, C–E) indicate β-galactosidase activity of meninges covered cortex. White arrowheads in F indicate choroid plexus. Abbreviations: C1, C1 vertebra; C2, C2 vertebra; CS, coronal suture; Cx, cortex; E, eye; EO, exoccipital bone; F, frontal bone; GE, ganglionic eminence; IP, interparietal bone; IS, interfrontal suture; N, nasal bone; P, parietal bone; SO, supraoccipital bone; Ve, ventricle. Scale bars: 1 mm in A–D, 0.2 in E, F.