Neuronal MHC-I proteins are in turn modulated by increase and decrease in electrical activity and by the neuronal transcription factors CREB, NPAS4 (in inhibitory neurons), and MECP2 (in the neuron-derived cell line N2A).134 Interestingly, mutation and dysregulation of CREB, NPAS4, and MECP2 have been found in autism.85,135. Here, NPAS4 is linked to autism.