DAG1 and lissencephaly spectrum disorders: Emx1Cre:Dag1 cKO and Emx1Cre:Pomt2 cKO mice show Type II lissencephaly consistent with severe dystroglycanopathy, whereas B4gat1M155T/M155T and FkrpP448L/P448L mutants have relatively normal cortical development consistent with mild dystroglycanopathy.