MECP2 and Rett syndrome: Mutations in the methyl-CpG-binding protein-2 gene (MECP2), which cause Rett syndrome (RTT), disrupt neuronal activity; however, the impact of the MECP2 loss-of-function on the cytoarchitecture of medial entorhinal cortex layer II (MECII) neurons—crucial for spatial memory and learning—remains poorly understood.