ARHGEF1 and microcephaly: After adjusting for body weight, both the head width (Figure 3D, Figure 3—figure supplement 1D) and brain weight (Figure 3E, Figure 3—figure supplement 1E) were reduced in P42 adult +/K1431M mice of both sexes relative to WT, consistent with the microcephaly seen in patients harboring TRIO GEF1-deficient alleles.