MECP2 and atypical Rett syndrome: Indeed, loss of MeCP2 protein, specifically in cholinergic neurons, has been shown to be a strong driver of Rett-like phenotypes, such as learning deficits46 and seizure susceptibility.34 Moreover, decreased levels of acetylcholine have been reported in multiple brain regions of female MeCP2-deficient gene knockout rats,47 suggesting how cholinergic neuron activity might be substantially decreased in Rett syndrome models.