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. Here, PCDH19 is linked to autism.