Human genetic studies have associated mutations in the neuron-specific type 2 K+/Cl− cotransporter KCC2 with the development of epilepsy (Kahle et al., 2014; Puskarjov et al., 2014; Stödberg et al., 2015; Saitsu et al., 2016; Saito et al., 2017; Till et al., 2019). The gene discussed is SLC12A5; the disease is epilepsy.