Expression of neural transcription factors in fetuses and along ESC differentiation. A, B, Western blotting shows temporal expression of Pax6 and Sox1 along human and mouse ESC differentiation. Arrowheads, Pax6a (lower) and Pax6b (upper). C, Pax6 and Sox2, but not Sox1, are expressed in the neural plate of day-18 and day-21 human fetuses, and Sox1 is detected in the brain and neural tube of day-26 human fetus. D, Sox1 and Sox2 are expressed throughout the mouse neural plate and neural tube from day-8 to 10.5 whereas Pax6 is absent in day-8 embryos but present in the forebrain and neural tube at day-10.5. Bright field images are provided in supplementary Figure 1. Scale Bars, 100 μm (C) and 50 μm (D).