HSP90AB1 and Rett syndrome: For example, GPS2 is a component of the nuclear receptor co-receptor (NCOR-SMRT) complex which interacts with methyl CpG binding protein 2 (MeCP2) to regulate silencing and has been implicated in the etiology of Rett syndrome [30], HSP90AB1 is elevated in ASD patients [31], and the potassium channel protein, KCND2 (Kv4.2), has been associated with a case of twins that were comorbid for ASD and seizures [32, 33].