The Tlx2-Cre mouse line was analyzed for β-galactosidase expression by crossing with the R26R reporter line. (a) Little or no expression of β-galactosidase was observed at 7.5 dpc. (b) Cre recombinase activity was observed at 8.5 dpc in caudal half of the embryo. (c) At 9.5, β-galactosidase expression is seen in the neural tube, lateral mesoderm, and otic vesicle. (d) Limited punctate expression of β-galactosidase was observed in yolk sac. (e) β-galactosidase expression is activated in the PNS by 10.5 dpc and remains expressed in the neural tube and lateral plate mesoderm but not in NC-derived cranial tissues. (f, g, h) Histological analysis of 9.5 dpc (f) and 10.5 dpc (g, h) embryos shows Cre activity in the dorsal neural tube, lateral mesoderm and the NC-derived sensory, sympathetic and enteric nervous systems. (i, j) β-galactosidase is not expressed in the outflow tract (oft) of the heart. ant: anterior, drg: dorsal root ganglia, ens: enteric nervous system, fg: forgut, h: heart, lm: lateral mesoderm, lv: left ventricle, nt: neural tube, oc: outflow tract cardiac cushion, oft: outflow tract, ov: otic vesicle, post: posterior, rv: right ventricle, sg: sympathetic ganglia, tg: trigeminal ganglia.