MAB21L3 and Rett syndrome: Our results indicated that the classical RTT subjects are likely to have a dysfunction in dopaminergic synapses due to functional variants in ATF6B (OMIM*600984) and PPP2R5E (OMIM*601647) genes encoding effectors of the postsynaptic cascade that follow binding of dopamine to D5 (OMIM+126453) receptor and D2 receptor (OMIM*126450), respectively (Table S1 in File S1 and Fig. 2a).