Analyses of teratomas. Ctrl and Q-KO ES cells were injected subcutaneously into nude mice. Teratomas were collected and sections were stained with haematoxylin and eosin (H&E), or analysed by immunohistochemistry with antibodies against beta III tubulin (a marker of immature postmitotic neuronal precursors), NeuN (a marker of mature neurons), GFAP (astrocytes), nestin (neural stem cells), Olig2 (oligodendrocytes), GATA6 (endoderm), or stained with Safranin O (to highlight mesoderm-derived skeletal muscle, cartilage and bone). Arrowheads point to Olig2- and GATA6- positive cells, and in the Safranin O panel to mesoderm-derived muscle (Ctrl) and bone (Q-KO). S, squamous epithelium; R, respiratory epithelium; N, neural tissue; F, fat; B, bone. Scale bars, 250 μM in (H&E panel) and 50 μM (all other panels). 12 Ctrl and 12 Q-KO teratomas (derived from 3 independent ES cell lines per genotype) were analysed by histology; sections from 2 teratomas per genotype were used for immunohistochemical confirmation of the identity of the lineages.