Fig. 6. Dosage-dependent requirement for Foxa1/2 in the differentiation of mDA neurons and a progressive rescue of mDA neuron number in mutant embryos during development. (A-C) Bar charts showing the number of immature (Nurr1⁺ TH^-) and mature (Nurr1⁺ TH⁺) neurons, as determined by immunohistochemistry, in embryos carrying 0-4 copies of Foxa1 and/or Foxa2 at three different stages. The x-axis shows the genotype of the mouse embryos, and the y-axis indicates the number of cells.