The gross structure of the brain on postnatal day 0 (P0) appeared normal in both Derl1NesCre mice (Figures S1E and S1F) and systemic Derl2 deletion mice (Derl2−/−) (Dougan et al., 2011); however, Derl1NesCre and Derl2NesCre mice demonstrated substantial microcephaly with significant reductions in brain size, weight, and whole volume at 37 weeks of age (Figures 1B–1D). Here, DERL2 is linked to microcephaly.