SLC38A1 and atypical Rett syndrome: In addition, SLC38A1, involved in neurotransmission at glutaminergic and GABAergic synapses (63), was downregulated in ASD relative to control STG. SLC38A1 is implicated in Rett Syndrome (64) and mitochondrial disorders, and its decrease may contribute to the observed alterations in synapse formation and neural connectivity.