ACTB and microcephaly: In addition, the extended network (Fig. 3B) contains several genes previously associated with an abnormal head circumference including ACTB in Baraitser-Winter syndrome (MIM #243310)[42], AKT1 in Proteus syndrome (MIM #176920)[43], CASK in Mental retardation and microcephaly with pontine and cerebellar hypoplasia (MIM #300749)[44], and NDE1 in microcephaly and lissencephaly[45,46].