RREB1 and microcephaly: At E9.0–9.5, Rreb1-/- embryos showed various defects, including microcephaly (2/7 at E9.5, Figure 2—figure supplement 1D), an open foregut (Figure 2—figure supplement 1E), and an open neural tube at the forebrain, midbrain, and posterior neuropore level (8/10 Rreb1-/- at E9.5, Figure 2D–E, Figure 2—figure supplement 1F).