Overexpression of Fgf8a by injection of Fgf8a mRNA in one blastomere at the 2-cell stage results in an expansion of the Runx1 expression domain. The expression domain of N-Tub and Ngnr1 is also expanded in these embryos. Knockdown of Fgf8a (Fgf8aMO) causes a severe reduction of all three genes. Similarly, interference with canonical Wnt signaling, by injection of Wnt8MO or β-catMO, reduces Runx1, N-Tub and Ngnr1 expression in all three populations of primary neurons. Expression of an activated form of Notch (Notch-ICD) also represses Runx1 expression. In all panels embryos are viewed from the dorsal side, anterior to top. The injected side is on the right.