Meanwhile, the remaining mutation associated with lissencephaly-4 (g.15691175_15691176GC > CT) stems from compound heterozygosity where one allele carries the mutation and the other allele is absent due to a microdeletion spanning the NDE1 locus (Figures 3A,B; Tan et al., 2017). Here, NDE1 is linked to lissencephaly 4.