In vivo CRISPRa decreases seizures and rescues cognitive deficits in a rodent model of epilepsy.

Epilepsy is a major health burden, calling for new mechanistic insights and therapies. CRISPR-mediated gene editing shows promise to cure genetic pathologies, although hitherto it has mostly been applied ex vivo. Its translational potential for treating non-genetic pathologies is still unexplored. Furthermore, neurological diseases represent an important challenge for the application of CRISPR, because of the need in many cases to manipulate gene function of neurons in situ. A variant of CRISPR, CRISPRa, offers the possibility to modulate the expression of endogenous genes by directly targeting their promoters. We asked if this strategy can effectively treat acquired focal epilepsy, focusing on ion channels because their manipulation is known be effective in changing network hyperactivity and hypersynchronziation. We applied a doxycycline-inducible CRISPRa technology to increase the expression of the potassium channel gene Kcna1 (encoding Kv1.1) in mouse hippocampal excitatory neurons. CRISPRa-mediated Kv1.1 upregulation led to a substantial decrease in neuronal excitability. Continuous video-EEG telemetry showed that AAV9-mediated delivery of CRISPRa, upon doxycycline administration, decreased spontaneous generalized tonic-clonic seizures in a model of temporal lobe epilepsy, and rescued cognitive impairment and transcriptomic alterations associated with chronic epilepsy. The focal treatment minimizes concerns about off-target effects in other organs and brain areas. This study provides the proof-of-principle for a translational CRISPR-based approach to treat neurological diseases characterized by abnormal circuit excitability.

Auditory Input Shapes Tonotopic Differentiation of Kv1.1 Expression in Avian Cochlear Nucleus during Late Development.

Tonotopic differentiation is fundamental for signal processing in the auditory system. However, when and how this differentiation arises remain elusive. We addressed this issue using electrophysiology and immunohistochemistry in nucleus magnocellularis of chickens of both sexes, which is known to differ in the expression of Kv1.1 channels depending on characteristic frequency (CF). Just after hearing onset (embryonic day 12-14), Kv1 current gradually increased to a slightly larger extent in neurons with higher CF, causing a tonotopic difference of Kv1 current before hatch. However, after hatch, a much larger increase of Kv1 current occurred, particularly in higher-CF neurons, due to an augmentation of Kv1.1 expression at the plasma membrane. This later change in expression led to the large tonotopic difference of Kv1 current characteristic of mature animals. Attenuation of auditory input by inducing conductive or sensorineural hearing loss around hatch suppressed the differentiation in a level-dependent manner. Moreover, elevation of auditory input during embryonic periods could not reproduce the differentiation, suggesting that the capacity of neurons to drive Kv1.1 expression via auditory input develops in a cell-specific manner, thus underlying the frequency-specific expression of the channel within the nucleus. The results indicated that the tonotopic differentiation of Kv1.1 in nucleus magnocellularis is partially determined before hatch, but largely driven by afferent input after hatch. Our results highlight the importance of neuronal capacity for sound to drive ion channel expression as well as the level of auditory experience in the frequency tuning of brainstem auditory circuits.SIGNIFICANCE STATEMENT Tuning-frequency-specific expression of ion channels is a prerequisite for auditory system function, but its underlying mechanisms remain unclear. Here, we revealed in avian cochlear nucleus that the expression of Kv1.1 became more dependent on auditory input at a late period of maturation in neurons tuned to higher-frequency sound, leading to frequency-specific Kv1.1 expression. Attenuation of auditory input during this period suppressed the differentiation in a level-dependent manner, whereas elevation of input in earlier periods could not reproduce the differentiation. Thus, the capacity of neurons to drive Kv1.1 expression via auditory input develops in a cell-specific manner and directs differentiation, highlighting the importance of neuronal character as well as the level of input in the frequency tuning of auditory circuits.

RNA editing in the central cavity as a mechanism to regulate surface expression of the voltage-gated potassium channel Kv1.1.

Voltage-gated potassium (Kv) 1.1 channels undergo a specific enzymatic RNA deamination, generating a channel with a single amino acid exchange located in the inner pore cavity (Kv1.1(I400V)). We studied I400V-edited Kv1.1 channels in more detail and found that Kv1.1(I400V) gave rise to much smaller whole-cell currents than Kv1.1. To elucidate the mechanism behind this current reduction, we conducted electrophysiological recordings on single-channel level and did not find any differences. Next we examined channel surface expression in Xenopus oocytes and HeLa cells using a chemiluminescence assay and found the edited channels to be less readily expressed at the surface membrane. This reduction in surface expression was verified by fluorescence imaging experiments. Western blot analysis for comparison of protein abundances and glycosylation patterns did not show any difference between Kv1.1 and Kv1.1(I400V), further indicating that changed trafficking of Kv1.1(I400V) is causing the current reduction. Block of endocytosis by dynasore or AP180C did not abolish the differences in current amplitudes between Kv1.1 and Kv1.1(I400V), suggesting that backward trafficking is not affected. Therefore, our data suggest that I400V RNA editing of Kv1.1 leads to a reduced current size by a decreased forward trafficking of the channel to the surface membrane. This effect is specific for Kv1.1 because coexpression of Kv1.4 channel subunits with Kv1.1(I400V) abolishes these trafficking effects. Taken together, we identified RNA editing as a novel mechanism to regulate homomeric Kv1.1 channel trafficking. Fine-tuning of Kv1.1 surface expression by RNA editing might contribute to the complexity of neuronal Kv channel regulation.

A mouse model of Schwartz-Jampel syndrome reveals myelinating Schwann cell dysfunction with persistent axonal depolarization in vitro and distal peripheral nerve hyperexcitability when perlecan is lacking.

Congenital peripheral nerve hyperexcitability (PNH) is usually associated with impaired function of voltage-gated K(+) channels (VGKCs) in neuromyotonia and demyelination in peripheral neuropathies. Schwartz-Jampel syndrome (SJS) is a form of PNH that is due to hypomorphic mutations of perlecan, the major proteoglycan of basement membranes. Schwann cell basement membrane and its cell receptors are critical for the myelination and organization of the nodes of Ranvier. We therefore studied a mouse model of SJS to determine whether a role for perlecan in these functions could account for PNH when perlecan is lacking. We revealed a role for perlecan in the longitudinal elongation and organization of myelinating Schwann cells because perlecan-deficient mice had shorter internodes, more numerous Schmidt-Lanterman incisures, and increased amounts of internodal fast VGKCs. Perlecan-deficient mice did not display demyelination events along the nerve trunk but developed dysmyelination of the preterminal segment associated with denervation processes at the neuromuscular junction. Investigating the excitability properties of the peripheral nerve suggested a persistent axonal depolarization during nerve firing in vitro, most likely due to defective K(+) homeostasis, and excluded the nerve trunk as the original site for PNH. Altogether, our data shed light on perlecan function by revealing critical roles in Schwann cell physiology and suggest that PNH in SJS originates distally from synergistic actions of peripheral nerve and neuromuscular junction changes.

Kv 1.1 is associated with neuronal apoptosis and modulated by protein kinase C in the rat cerebellar granule cell.

Previously, we reported that apoptosis of cerebellar granular neurons induced by low-K+ and serum-free (LK-S) was associated with an increase in the A-type K+ channel current (I(A)), and an elevated expression of main alpha-subunit of the I(A) channel, which is known as Kv4.2 and Kv4.3. Here, we show, as assessed by quantitative RT-PCR and whole-cell recording, that besides Kv4.2 and Kv4.3, Kv1.1 is very important for I(A) channel. The expression of Kv1.1 was elevated in the apoptotic neurons, while silencing Kv1.1 expression by siRNA reduced the I(A) amplitude of the apoptotic neuron, and increased neuron viability. Inhibiting Kv1.1 current by dendrotoxin-K evoked a similar effect of reduction of I(A) amplitude and protection of neurons. Applying a protein kinase C (PKC) activator, phorbol ester acetate A (PMA) mimicked the LK-S-induced neuronal apoptotic effect, enhanced the I(A) amplitude and reduced the granule cell viability. The PKC inhibitor, bisindolylmaleimide I and Gö6976 protected the cell against apoptosis induced by LK-S. After silencing the Kv1.1 gene, the effect of PMA on the residual K+ current was reduced significantly. Quantitative RT-PCR and Western immunoblot techniques revealed that LK-S treatment and PMA increased the level of the expression of Kv1.1, in contrast, bisindolylmaleimide I inhibited Kv1.1 expression. In addition, the activation of the PKC isoform was identified in apoptotic neurons. We thus conclude that in the rat cerebellar granule cell, the I(A) channel associated with apoptotic neurons is encoded mainly by the Kv1.1 gene, and that the PKC pathway promotes neuronal apoptosis by a brief modulation of the I(A) amplitude and a permanent increase in the levels of expression of the Kv1.1 alpha-subunit.

4-methyl benzylamine stimulates food consumption and counteracts the hypophagic effects of amphetamine acting on brain Shaker-like Kv1.1 channels.

1.--4-methyl benzylamine (4-MBZ; 28 microg, 231 nmol) elicits a hyperphagic response in starved mice in contrast to the hypophagia induced by the parent compound benzylamine (BZ; 33 microg, 231 nmol) or by amphetamine (AMPH, 2 mug). 2.--In mice starved for only 4 h, and therefore with little stimulation to eat, the maximal increase in food consumption induced by intracerebroventricular (i.c.v.)-injected 4-MBZ was 190% over that of the controls (ED(50) 8.3+/-2.7 microg mouse(-1); 68+/-22 nmol mouse(-1)), whereas after i.p. administration, these values were 160% and approximately 129 mg kg(-1), respectively. 3.--The hyperphagic effect of 4-MBZ was reduced by more than 60% in mice pretreated with antisense oligodeoxyribonucleotide (aODN(1)) previously found to selectively inhibit (over 50%) the expression of Shaker-like Kv1.1 channels. 4.--In mice highly stimulated to eat after 12-h fasting, 4-MBZ (28 microg) significantly reduced (to about 70%) the hypophagic response by AMPH (2 microg) or BZ (33 microg). Conversely, these two compounds reduced (respectively, by 69 and 44%) the hyperphagic response of 4-MBZ in 4-h fasting mice. 5.--4-MBZ (28 microg) also reduced the hypermotility and the stimulation of inspection activity elicited by AMPH in mice and the release of DA stimulated by AMPH (2 microg) from the nucleus accumbens of rats. We hypothesize that 4-MBZ elicits hyperphagic effects probably by opening Shaker-like Kv1.1 subtypes in the brain, whereas AMPH and BZ are hypophagic by blocking these channels.

Effects of voltage-gated K+ channel blockers in gefitinib-resistant H460 non-small cell lung cancer cells.

Voltage-gated K(+) (Kv) channels are known to be associated with the proliferation of several types of cancer cells, including lung adenocarcinoma cells, and certain Kv channel blockers inhibit cancer cell proliferation. In the present study, we investigated the effects of Kv channel blockers in gefitinib-resistant H460 non-small cell lung cancer (NSCLC) cells. Treatment with dendrotoxin-κ (DTX-κ), which is a Kv1.1-specific blocker, reduced H460 cell viability and arrested cells in G(1)/S transition during cell-cycle progression. We administered DTX-κ in a xenograft model using nude mice. The tumor volume was reduced by the injection of DTX-κ into the tumor tissues compared to the control group. These results indicate that DTX-κ has antitumor effects in gefitinib-resistant H460 cells through the pathway governing the G(1)/S transition both in vitro and in vivo. These findings suggest that Kv1.1 could serve as a novel therapeutic target for gefitinib-resistant NSCLC.

Expression of glutamate receptors and potassium channels in vestibular nuclei neurons during development of signal processing.

The principal cells of the chick tangential vestibular nucleus offer a simple neuron model to study signal processing in second-order, vestibular reflex projection neurons. The principal cells represent a relatively uniform population of vestibular nuclei neurons which receive a major input from the primary vestibular fibers and send axons to targets mainly involved in the vestibuloocular reflexes. Here, studies performed on ion channels involved in the emergence and establishment of signal processing in this morphologically-identified subset of vestibular nuclei neurons are reviewed, including the AMPA glutamate receptor subunits GluR1, GluR2, GluR3, and GluR4 and the potassium channel subunits Kv1.1 and Kv1.2.

Voltage-gated delayed rectifier K v 1-subunits may serve as distinctive markers for enteroglial cells with different phenotypes in the murine ileum.

Due to entangled results concerning K(v)1 subunit distribution in the gastrointestinal wall, we aimed to unravel the expression of the delayed rectifier potassium subunits K(v)1.1 and K(v)1.2 in the murine ileum. Presence and distribution of both subunits were determined in cryosections and whole-mount preparations of the ileum of three different murine strains by indirect immunofluorescence, and analysed by conventional fluorescence and confocal microscopy. Distribution of both subunits was similar in the ileum of the three strains. K(v)1.1 immunoreactivity (IR) was found in some S100-expressing enteroglial cells (EGC) located at the periphery of myenteric ganglia, in S100-positive EGC along interganglionic, intramuscular and vascular nerve fibres, and in S100-positive EGC of the submucous plexus. K(v)1.1 IR was also observed in some GFAP-expressing EGC at the periphery of myenteric ganglia, and in GFAP-positive EGC of submucous ganglia. K(v)1.2 IR was detected in some intramuscular S100-positive EGC, in almost all submucous S100-expressing EGC, and in a few GFAP-expressing EGC. K(v)1.2 IR was also expressed in a majority of enteric neurons. Coding of these neurons showed that all cholinergic and most nitrergic neurons express K(v)1.2. In conclusion, the results showed that K(v)1.1 and K(v)1.2 were predominantly expressed in distinct EGC phenotypes. K(v)1.2 was also observed in distinct neuron subpopulations. Our results support the active role of EGC with distinct phenotypes in intestinal functions, which is relevant in view of their modulating role on intestinal barrier and inflammatory responses.

Kv1 potassium channel C-terminus constant HRETE region: arginine substitution affects surface protein level and conductance level of subfamily members differentially.

We have shown previously that truncating all of the variable cytoplasmic C-terminus of Kv1.1 potassium channels to G421stop had only a small inhibitory effect on their cell surface conductance density levels and cell surface protein levels. Here we investigated the role of a highly conserved cytoplasmic C-terminal charged region of five amino acids (HRETE) of the S6 transmembrane domain in the protein and conductance expression of Kv1.1, Kv1.2, and Kv1.4 channels. For Kv1.1 we found that E420stop, T419stop, and E418stop showed cell surface conductance densities and cell surface protein levels similar to full length control, whereas R417stop and H416stop exhibited essentially no conductance but their surface protein levels were similar to full length control. A bulky non-negatively charged hydrophilic amino acid at position 417 appeared to be critical for wild type gating of Kv1.1 because R417K and R417Q rescued conductance levels whereas R417A or R417E did not. The R417A mutation in the full length Kv1.1 also exhibited surface protein levels similar to control but it did not exhibit significant conductance. In contrast, mutation of the equivalent arginine to alanine in full length Kv1.2 and Kv1.4 appeared to have little or no effect on channel conductance but rather decreased cell surface protein levels by inducing partial high ER retention. These findings are consistent with the notion that the arginine amino acid in the HRETE region plays a different role in affecting conductance levels or cell surface protein levels of very closely related Kv1 potassium channels.

Activity- and mTOR-dependent suppression of Kv1.1 channel mRNA translation in dendrites.

Mammalian target of rapamycin (mTOR) is implicated in synaptic plasticity and local translation in dendrites. We found that the mTOR inhibitor, rapamycin, increased the Kv1.1 voltage-gated potassium channel protein in hippocampal neurons and promoted Kv1.1 surface expression on dendrites without altering its axonal expression. Moreover, endogenous Kv1.1 mRNA was detected in dendrites. Using Kv1.1 fused to the photoconvertible fluorescence protein Kaede as a reporter for local synthesis, we observed Kv1.1 synthesis in dendrites upon inhibition of mTOR or the N-methyl-d-aspartate (NMDA) glutamate receptor. Thus, synaptic excitation may cause local suppression of dendritic Kv1 channels by reducing their local synthesis.