Genetic variation in SLC12A5 which encodes KCC2, the neuron-specific cation-chloride cotransporter that is essential for hyperpolarizing GABAergic signaling and formation of cortical dendritic spines, has not been reported in human disease. Screening of SLC12A5 revealed a co-segregating variant (KCC2-R952H) in an Australian family with febrile seizures. We show that KCC2-R952H reduces neuronal Cl− extrusion and has a compromised ability to induce dendritic spines in vivo and in vitro. Biochemical analyses indicate a reduced surface expression of KCC2-R952H which likely contributes to the functional deficits. Our data suggest that KCC2-R952H is a bona fide susceptibility variant for febrile seizures.

Concepts of epilepsy, based on a simple change in neuronal excitation/inhibition balance, have subsided in face of recent insights into the large diversity and context-dependence of signaling mechanisms at the molecular, cellular and neuronal network level. GABAergic transmission exerts both seizure-suppressing and seizure-promoting actions. These two roles are prone to short-term and long-term alterations, evident both during epileptogenesis and during individual epileptiform events. The driving force of GABAergic currents is controlled by ion-regulatory molecules such as the neuronal K-Cl cotransporter KCC2 and cytosolic carbonic anhydrases. Accumulating evidence suggests that neuronal ion regulation is highly plastic, thereby contributing to the multiple roles ascribed to GABAergic signaling during epileptogenesis and epilepsy.

Cerebellar cortical throughput involved in motor control comprises granule cells (GCs) and Purkinje cells (PCs), both of which receive inhibitory GABAergic input from interneurons. The GABAergic input to PCs is essential for learning and consolidation of the vestibulo‐ocular reflex, but the role of GC excitability remains unclear. We now disrupted the Kcc2 K‐Cl cotransporter specifically in either cell type to manipulate their excitability and inhibition by GABAA‐receptor Cl− channels. Although Kcc2 may have a morphogenic role in synapse development, Kcc2 disruption neither changed synapse density nor spine morphology. In both GCs and PCs, disruption of Kcc2, but not Kcc3, increased [Cl−]i roughly two‐fold. The reduced Cl− gradient nearly abolished GABA‐induced hyperpolarization in PCs, but in GCs it merely affected excitability by membrane depolarization. Ablation of Kcc2 from GCs impaired consolidation of long‐term phase learning of the vestibulo‐ocular reflex, whereas baseline performance, short‐term gain‐decrease learning and gain consolidation remained intact. These functions, however, were affected by disruption of Kcc2 in PCs. GC excitability plays a previously unknown, but specific role in consolidation of phase learning.

SignificanceThe transition from placental to lung-based oxygen supply at mammalian birth involves an obligatory period of asphyxia, which is further aggravated by complications during delivery. This oxygen deprivation is a major threat to the fetal brain, and, under such conditions, hormonal and cardiovascular mechanisms are activated to enhance brain perfusion. Our work now demonstrates an intrinsic mechanism in the fetal brain whereby vasopressin activates hippocampal interneurons, leading to desynchronization and suppression of neuronal network activity in species (rat and guinea pig) that are born at widely different stages of brain maturation. Silencing of synchronous neuronal activity by vasopressin is expected to decrease neuronal energy demand and prevent maladaptive synaptic plasticity, thus acting as a pan-mammalian neuroprotective mechanism during birth.

The authors regret that the description of the synthesis of bumepamine in the above-mentioned article lacked an important aspect and is therefore incorrect.The correct synthesis of bumepamine is given below. The authors would like to apologise for any inconvenience caused. Synthesis of bumepamineBumetanide (1) (500 mg, 1.37 mmol) was dissolved in 9 mL dry N, N-dimethylformamide and N,N-diisopropylethylamine (765 μL, 4.39 mmol), followed by addition of aniline (250 μL, 2.74 mmol). The mixture was cooled on an ice-bath. COMU (707 mg, 1.65 mmol) was added in one portion and the mixture was gradually warmed to room temperature and stirred for 16 h. The reaction was quenched with saturated aqueous NaHCO 3 solution and extracted twice with ethyl acetate (EtOAc). The combined organic layers were washed with water, brine and dried over Na 2 SO 4 . The crude product was purified by column chromatography (toluene:EtOAc:Et 3 N, 3:2:0.01). The desired product (2; the phenylamide of bumetanide) (540 mg, 1.22 mmol) was obtained in 89% yield as a slightly yellow solid. 1 H NMR (400 MHz, d 4 -MeOH) δ 7.79 (d, J = 2.1 Hz, 1H), 7.68-7.71 (m, 2H), 7.50 (d, J = 2.1 Hz, 1H), 7.36-7.40 (m, 2H), 7.28-7.32 (m, 2H), 7.14-7.19 (m, 1H), 7.05-7.09 (m, 1H), 6.93-6.96 (m, 2H), 3.17 (t, J = 6.7 Hz, 2H), 1.40-1.48 (m, 2H), 1.13-1.21 (m, 2H), 0.83 (t, J = 7.3 Hz, 3H). 13 C NMR (100 MHz) d 4 -calculated for C 23 H 26 N 3 O 4 S [M+H] + 440.1644, found 440.1646.Next, the phenylamide of bumetanide (2) (250 mg, 0.57 mmol) was dissolved in 12 mL tetrahydrofuran and borane dimethylsulfide complex (90 μL, 0.95 mmol) was added at room temperature. The reaction mixture was stirred for 16 h at 70°C and cooled to room temperature. Since some starting material was still present, an additional amount of the borane dimethylsulfide complex (90 μL, 0.95 mmol) was added and the reaction was stirred for 5 h at 70°C. The reaction mixture was cooled to room temperature and then quenched with half-saturated aqueous NaHCO 3 solution. The mixture was extracted three times with EtOAc and the combined organic layers were dried over Na 2 SO 4 . The crude product was purified by column chromatography (CH 2 Cl 2 :MeOH, 50:1). The obtained oily substance was dried under vacuum for 4 hours and then dissolved in 10 mL dry diethyl ether (Et 2 O). 2M HCl in Et 2 O (135 μL, 0.27 mmol) was added and the flask left to stand for 10 minutes. The salt that was formed was filtered, washed three times with Et 2 O and the desired product (3; bumepamine) (90 mg, 0.21 mmol) was obtained as a slightly beige solid in 37% yield. 1 H NMR (400 MHz, d 4 -MeOH) δ 7.52-7.60 (m, 3H), 7.44-7.46 (m, 2H), 7.33 (d, J = 2.0 Hz, 1H), 7.68-7.30 (m, 2H), 7.04-7.08 (m, 1H), 6.92 (d, J = 2.0 Hz, 1H), 6.86-6.89 (m, 2H), 4.64 (s, 2H), 3.00 (t, J = 6.8 Hz, 2H), 1.29-1.37 (m, 2H), 1.06-1.15 (m, 2H), 0.80 (t, J = 7.4 Hz, 3H). 13 C NMR (100 MHz) d 4 -