ARSD and Anxiety: Among the known rodent (i.e. mouse) models for PCDH19 dysregulation that reported milder brain developmental phenotypes, only some displayed also behavioural phenotypes (i.e. ASD-related behaviours in Pcdh19XLacZ/X, Pcdh19X+/X and Pcdh19X−/Y mice22,23 cognitive impairments in Pcdh19+/− females, but not Pcdh19−/y male mice25) reduced anxiety and increased exploratory behaviour both in Pcdh19X+/X and Pcdh19X−/Y,26 whereas in some others, behaviours were not investigated (i.e. Pcdh19HA-FLAG/β-Geo and Pcdh19+/β-Geo11,21  Table 3).