PCDH19 and developmental and epileptic encephalopathy, 9: Since it is not possible to obtain all female genotypes (wild-type, heterozygous and homozygous) as littermates in our mating protocol (see Methods) and also human EFMR occurs exclusively in heterozygous mutants of the PCDH19 gene, we compared only wild-type and heterozygous mutant mice in the female behavioral experiments.