ZIC4 and Cerebellar hypoplasia: In the case of ZIC1, the observation that heterozygous deletions in tandem with ZIC4 cause DWM18,36 has supported work in Xenopus27,38,40 and mouse,20,41 indicating key roles for the Zic1 ortholog in neurogenesis (in the mouse, deficiency of Zic1 and Zic4 contribute additively to cerebellar hypoplasia).20