Primary aldosteronism, a common cause of severe hypertension1, features constitutive production of the adrenal steroid aldosterone. We analyzed a multiplex family with familial hyperaldosteronism type II (FH-II)2 and 80 additional probands with unsolved early-onset primary aldosteronism. Eight probands had novel heterozygous variants in CLCN2, including two de novo mutations and four independent occurrences of the identical p.Arg172Gln mutation; all relatives with early-onset primary aldosteronism carried the CLCN2 variant found in probands. CLCN2 encodes a voltage-gated chloride channel expressed in adrenal glomerulosa that opens at hyperpolarized membrane potentials. Channel opening depolarizes glomerulosa cells and induces expression of aldosterone synthase, the rate-limiting enzyme for aldosterone biosynthesis. Mutant channels cause gain of function, with higher open probabilities at the glomerulosa resting potential. These findings for the first time demonstrate a role of anion channels in glomerulosa membrane potential determination, aldosterone production and hypertension. They establish the cause of a substantial fraction of early-onset primary aldosteronism.

Highlights Extracellular levels of norepinephrine display dynamic changes during NREM and REM sleep  Phasic activity of locus coeruleus neurons during NREM underlies slow norepinephrine oscillations  Spindles occur at norepinephrine troughs and are abolished by norepinephrine increases  Increased spindles prior to REM reflect the beginning of a long-lasting norepinephrine decline  REM episodes are characterized by a sub-threshold continuous norepinephrine decline  The responsiveness of astrocytic Ca 2+ to norepinephrine is reduced during sleep

Astrocytic volume regulation and neurotransmitter uptake are critically dependent on the intracellular anion concentration, but little is known about the mechanisms controlling internal anion homeostasis in these cells. Here we used fluorescence lifetime imaging microscopy (FLIM) with the chloride-sensitive dye MQAE to measure intracellular chloride concentrations in murine Bergmann glial cells in acute cerebellar slices. We found Bergmann glial [Cl ] to be controlled by two opposing transport processes: chloride is actively accumulated by the Na -K -2Cl cotransporter NKCC1, and chloride efflux through anion channels associated with excitatory amino acid transporters (EAATs) reduces [Cl ] to values that vary upon changes in expression levels or activity of these channels. EAATs transiently form anion-selective channels during glutamate transport, and thus represent a class of ligand-gated anion channels. Age-dependent upregulation of EAATs results in a developmental chloride switch from high internal chloride concentrations (51.6 ± 2.2 mM, mean ± 95% confidence interval) during early development to adult levels (35.3 ± 0.3 mM). Simultaneous blockade of EAAT1/GLAST and EAAT2/GLT-1 increased [Cl ] in adult glia to neonatal values. Moreover, EAAT activation by synaptic stimulations rapidly decreased [Cl ] . Other tested chloride channels or chloride transporters do not contribute to [Cl ] under our experimental conditions. Neither genetic removal of ClC-2 nor pharmacological block of K -Cl cotransporter change resting Bergmann glial [Cl ] in acute cerebellar slices. We conclude that EAAT anion channels play an important and unexpected role in adjusting glial intracellular anion concentration during maturation and in response to cerebellar activity. GLIA 2017;65:388-400.

No abstract

Episodic ataxia type 6 is an inherited neurological condition characterized by combined ataxia and epilepsy. A severe form of this disease with episodes combining ataxia, epilepsy and hemiplegia was recently associated with a proline to arginine substitution at position 290 of the excitatory amino acid transporter 1 in a heterozygous patient. The excitatory amino acid transporter 1 is the predominant glial glutamate transporter in the cerebellum. However, this glutamate transporter also functions as an anion channel and earlier work in heterologous expression systems demonstrated that the mutation impairs the glutamate transport rate, while increasing channel activity. To understand how these changes cause ataxia, we developed a constitutive transgenic mouse model. Transgenic mice display epilepsy, ataxia and cerebellar atrophy and, thus, closely resemble the human disease. We observed increased glutamate-activated chloride efflux in Bergmann glia that triggers the apoptosis of these cells during infancy. The loss of Bergmann glia results in reduced glutamate uptake and impaired neural network formation in the cerebellar cortex. This study shows how gain-of-function of glutamate transporter-associated anion channels causes ataxia through modifying cerebellar development.

Alexei Verkhratsky is an internationally recognised scholar in the field of cellular neurophysiology. His research is concentrated on the mechanisms of inter-and intracellular signalling in the CNS, being especially focused on two main types of neural cells, on neurones and neuroglia. He made important contributions to understanding chemical and electrical transmission in reciprocal neuronal-glial communications and the role of intracellular Ca 2+ signals in integrative processes in the nervous system. Many of his studies are dedicated to investigations of cellular mechanisms of neurodegeneration. He was the first to perform intracellular Ca 2+ recordings in old neurones in isolation and in situ, which provided direct experimental support for the 'Ca 2+ hypothesis of neuronal ageing' . In recent years he has studied glial ageing and gliopathology in age-related brain diseases, including Alzheimer's disease and neuropsychiatric diseases. He authored a pioneering hypothesis of astroglial atrophy as a general mechanism of cognitive brain disorders including neurodegenerative and psychiatric diseases. He was among 30 most-cited European neuroscientists in 2016.

Information transfer within neuronal circuits depends on the balance and recurrent activity of excitatory and inhibitory neurotransmission. Chloride (Cl−) is the major central nervous system (CNS) anion mediating inhibitory neurotransmission. Astrocytes are key homoeostatic glial cells populating the CNS, although the role of these cells in regulating excitatory-inhibitory balance remains unexplored. Here we show that astrocytes act as a dynamic Cl− reservoir regulating Cl− homoeostasis in the CNS. We found that intracellular chloride concentration ([Cl−]i) in astrocytes is high and stable during sleep. In awake mice astrocytic [Cl−]i is lower and exhibits large fluctuation in response to both sensory input and motor activity. Optogenetic manipulation of astrocytic [Cl−]i directly modulates neuronal activity during locomotion or whisker stimulation. Astrocytes thus serve as a dynamic source of extracellular Cl− available for GABAergic transmission in awake mice, which represents a mechanism for modulation of the inhibitory tone during sustained neuronal activity.

PTSNtr is a regulatory phosphotransferase system in many bacteria. Mutation of the PTSNtr enzymes causes pleiotropic growth phenotypes, dry colony morphology and a posttranslational inactivation of ABC transporters in Rhizobium leguminosarum 3841. The PTSNtr proteins EINtr and 2 copies of EIIANtr have been described previously. Here we identify the intermediate phosphocarrier protein NPr and show its phosphorylation by EINtr in vitro. Furthermore we demonstrate that phosphorylation of EINtr and NPr is required for ABC transport activation and that the N-terminal GAF domain of EINtr is not required for autophosphorylation. Previous studies have shown that non-phosphorylated EIIANtr is able to modulate the transcriptional activation of the high affinity potassium transporter KdpABC. In R. leguminosarum 3841 kdpABC expression strictly depends on EIIANtr. Here we demonstrate that under strong potassium limitation ABC transport is inactivated, presumably by non-phosphorylated EIIANtr. This is to our knowledge the first report where PTSNtr dictates an essential cellular function. This is achieved by the inverse regulation of two important ATP dependent transporter classes.