We do not yet know how the complete loss of Pcdh19 causes autism-like behaviors in male mice, but considering the fact that the abnormal segregation pattern occurs only in the brain of female heterozygous Pcdh19 KO mice [9, 13], but not in male KO mice, our present findings suggest the mechanism will be distinct from the cellular interference mechanism that underlies the epileptic symptoms of EFMR. This evidence concerns the gene PCDH19 and developmental and epileptic encephalopathy, 9.