SLC6A1 (Solute Carrier Family 6 Member 1) is a gene encoding GAT1, the gamma-aminobutyric acid (GABA) transporter protein. GAT1 is responsible for GABA reuptake from the synaptic cleft and intercellular space. Mutations in the SLC6A1 gene can lead to impaired GABA regulation and are associated with epilepsy and a number of mental disorders. In this review, we discuss the role of GAT1 protein in GABAergic regulation and the association of mutations in SLC6A1 gene with epilepsy, autism spectrum disorders, intellectual disability, and schizophrenia, as well as prospects for their treatment with genome editing systems.