Other examples of the functional overlap of the genes are glutamate ionotropic receptor NMDA type subunit 1 (GRIN1) and glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A), both of which are essential in excitatory neurotransmission, verbal memory, and cognitive function, probably through regulating the patterning of neuron dendritic arborizations [63,64,70,71,72,73], which is similar to the impacts caused due to RTT mutations. The gene discussed is GRIN1; the disease is Rett syndrome.