PCDH19 and Down syndrome: Initially we investigated and confirmed the presence of several Down syndrome-related risk proteins in the synaptic proteome of Ts65Dn mice, including ARID1B, CCT8, DYRK1A, EZR, GART, INA, ITSN1, MRPL39, PCDH19, SNX9, and SYNJ1 [45,46,47,48].