MECP2 and atypical Rett syndrome: In particular, microglia are known to affect synapse number in co-culture with neurons, a process that is highly dependent on their inflammatory state and their cytokine expression profile.11,42 It has previously been reiterated that MeCP2 is a protein highly involved in synaptogenesis and, to add to that hypothesis, synaptic deficits as in spine numbers and motility have been described in murine models of Rett syndrome.43,44 We thus tested whether and how microglial cells could contribute to the synaptic deficits in an in vitro microglia-neuron co-culture model.