Erythropoietin receptor expression in mice during brain development. (a) Quantification of EpoR mRNA in mouse brain (circles) compared with liver (triangles) beginning at embryonic day E10 from Liu et al., [68]. (b) Hypoplasia of neuroepithelium of the fourth ventricle at embryonic day E12.5 in embryo (right) compared with embryo (left) (bars, 0.4 mm) from Yu et al., [69].