NPC1 and early-onset autosomal dominant Alzheimer disease: PRNP,which has been associated with Alzheimer’s disease,has also been reported in intercellular signal transmission and interactionbetween signaling pathways.70,71 Thus, although themajor effect of RTT has not been observed for the NPC group pathways,it may still have a role in the early stages of RTT by deteriorationof cellular processes.