A New Kv1.2 Channelopathy Underlying Cerebellar Ataxia

A forward genetic screen of mice treated with the mutagen ENU identified a mutant mouse with chronic motor incoordination. This mutant, named Pingu (Pgu), carries a missense mutation, an I402T substitution in the S6 segment of the voltage-gated potassium channel Kcna2. The gene Kcna2 encodes the voltage-gated potassium channel α-subunit Kv1.2, which is abundantly expressed in the large axon terminals of basket cells that make powerful axo-somatic synapses onto Purkinje cells. Patch clamp recordings from cerebellar slices revealed an increased frequency and amplitude of spontaneous GABAergic inhibitory postsynaptic currents and reduced action potential firing frequency in Purkinje cells, suggesting that an increase in GABA release from basket cells is involved in the motor incoordination in Pgu mice. In line with immunochemical analyses showing a significant reduction in the expression of Kv1 channels in the basket cell terminals of Pgu mice, expression of homomeric and heteromeric channels containing the Kv1.2(I402T) α-subunit in cultured CHO cells revealed subtle changes in biophysical properties but a dramatic decrease in the amount of functional Kv1 channels. Pharmacological treatment with acetazolamide or transgenic complementation with wild-type Kcna2 cDNA partially rescued the motor incoordination in Pgu mice. These results suggest that independent of known mutations in Kcna1 encoding Kv1.1, Kcna2 mutations may be important molecular correlates underlying human cerebellar ataxic disease. A forward genetic screen of mice treated with the mutagen ENU identified a mutant mouse with chronic motor incoordination. This mutant, named Pingu (Pgu), carries a missense mutation, an I402T substitution in the S6 segment of the voltage-gated potassium channel Kcna2. The gene Kcna2 encodes the voltage-gated potassium channel α-subunit Kv1.2, which is abundantly expressed in the large axon terminals of basket cells that make powerful axo-somatic synapses onto Purkinje cells. Patch clamp recordings from cerebellar slices revealed an increased frequency and amplitude of spontaneous GABAergic inhibitory postsynaptic currents and reduced action potential firing frequency in Purkinje cells, suggesting that an increase in GABA release from basket cells is involved in the motor incoordination in Pgu mice. In line with immunochemical analyses showing a significant reduction in the expression of Kv1 channels in the basket cell terminals of Pgu mice, expression of homomeric and heteromeric channels containing the Kv1.2(I402T) α-subunit in cultured CHO cells revealed subtle changes in biophysical properties but a dramatic decrease in the amount of functional Kv1 channels. Pharmacological treatment with acetazolamide or transgenic complementation with wild-type Kcna2 cDNA partially rescued the motor incoordination in Pgu mice. These results suggest that independent of known mutations in Kcna1 encoding Kv1.1, Kcna2 mutations may be important molecular correlates underlying human cerebellar ataxic disease. IntroductionVoltage-gated potassium channels play a key role in neuronal excitability and plasticity and are critical in establishing resting membrane potential and firing thresholds, repolarizing action potentials, and limiting excitability (1Hille B. Ionic Channels of Excitable Membranes. Sinauer, Sunderland, MA2001Google Scholar). Channels are unevenly distributed throughout the brain as a whole and also within individual neurons (2Trimmer J.S. Proc. Natl. Acad. Sci. U.S.A. 1991; 88: 10764-10768Crossref PubMed Scopus (213) Google Scholar, 3Drewe J.A. Verma S. Frech G. Joho R.H. J. Neurosci. 1992; 12: 538-548Crossref PubMed Google Scholar, 4Hwang P.M. Glatt C.E. Bredt D.S. Yellen G. Snyder S.H. Neuron. 1992; 8: 473-481Abstract Full Text PDF PubMed Scopus (103) Google Scholar, 5Hwang P.M. Fotuhi M. Bredt D.S. Cunningham A.M. Snyder S.H. J. Neurosci. 1993; 13: 1569-1576Crossref PubMed Google Scholar, 6Wang H. Kunkel D.D. Martin T.M. Schwartzkroin P.A. Tempel B.L. Nature. 1993; 365: 75-79Crossref PubMed Scopus (515) Google Scholar, 7Wang H. Kunkel D.D. Schwartzkroin P.A. Tempel B.L. J. Neurosci. 1994; 14: 4588-4599Crossref PubMed Google Scholar, 8McNamara N.M. Muniz Z.M. Wilkin G.P. Dolly J.O. Neuroscience. 1993; 57: 1039-1045Crossref PubMed Scopus (52) Google Scholar, 9McNamara N.M. Averill S. Wilkin G.P. Dolly J.O. Priestley J.V. Eur. J. Neurosci. 1996; 8: 688-699Crossref PubMed Scopus (36) Google Scholar, 10Sheng M. Tsaur M.L. Jan Y.N. Jan L.Y. J. Neurosci. 1994; 14: 2408-2417Crossref PubMed Google Scholar). Therefore, the particular utility of any given channel depends not only on its specific channel properties and stoichiometry but also on its particular localization and density within a cell or cellular compartment. In the cerebellum, the genes Kcna1 and Kcna2 encode the voltage-gated potassium channel subunits Kv1.1 and Kv1.2, respectively, which contribute to the low voltage-activated potassium current IKv1 and are coexpressed in the presynaptic GABAergic pinceaus of spontaneously firing basket cell interneurons that provide a strong inhibitory input to Purkinje cells (5Hwang P.M. Fotuhi M. Bredt D.S. Cunningham A.M. Snyder S.H. J. Neurosci. 1993; 13: 1569-1576Crossref PubMed Google Scholar, 6Wang H. Kunkel D.D. Martin T.M. Schwartzkroin P.A. Tempel B.L. Nature. 1993; 365: 75-79Crossref PubMed Scopus (515) Google Scholar, 7Wang H. Kunkel D.D. Schwartzkroin P.A. Tempel B.L. J. Neurosci. 1994; 14: 4588-4599Crossref PubMed Google Scholar, 8McNamara N.M. Muniz Z.M. Wilkin G.P. Dolly J.O. Neuroscience. 1993; 57: 1039-1045Crossref PubMed Scopus (52) Google Scholar, 9McNamara N.M. Averill S. Wilkin G.P. Dolly J.O. Priestley J.V. Eur. J. Neurosci. 1996; 8: 688-699Crossref PubMed Scopus (36) Google Scholar). The shunting effect of this inhibitory conductance has been shown through modeling to have a steep correlation with the prolongation of Purkinje cell interspike intervals in vitro (11Jaeger D. De Schutter E. Bower J.M. J. Neurosci. 1997; 17: 91-106Crossref PubMed Google Scholar, 12Jaeger D. Bower J.M. J. Neurosci. 1999; 19: 6090-6101Crossref PubMed Google Scholar, 13Walter J.T. Alviña K. Womack M.D. Chevez C. Khodakhah K. Nat. Neurosci. 2006; 9: 389-397Crossref PubMed Scopus (319) Google Scholar).The cerebellum is involved in the regulation of the initiation and timing of movements and is important for maintaining balance and posture (14Morton S.M. Bastian A.J. Cerebellum. 2007; 6: 79-86Crossref PubMed Scopus (131) Google Scholar). At the core of the cerebellar computational circuitry, the spontaneously spiking Purkinje cells integrate cerebral cortical and sensory, excitatory and inhibitory inputs encoding relevant information in their action potential discharge and communicate the information to the deep cerebellar nuclei for the final output of the cerebellum (15Bower J.M. Ann. N. Y. Acad. Sci. 2002; 978: 135-155Crossref PubMed Scopus (92) Google Scholar). The total synaptic conductance invading a Purkinje cell effectively functions to clamp the subthreshold membrane voltage, thereby controlling the state of the active conductances that determine each Purkinje cell intrinsic pacemaking activity, which in turn shapes the tonic GABAergic inhibition targeted to the deep cerebellar nuclei (11Jaeger D. De Schutter E. Bower J.M. J. Neurosci. 1997; 17: 91-106Crossref PubMed Google Scholar).Missense mutations of Kcna1 are associated with type 1 episodic ataxia (EA1) 3The abbreviations used are: EA1type 1 episodic ataxiaIPSCinhibitory postsynaptic currentsIPSCspontaneous IPSCmIPSCminiature IPSCATZacetazolamideGABAγ-aminobutyric acidNSEneuron-specific enolaseSNPsingle nucleotide polymorphismTTXtetrodotoxinpFpicofaradsNBQX2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dioneMbmegabase. (16Browne D.L. Gancher S.T. Nutt J.G. Brunt E.R. Smith E.A. Kramer P. Litt M. Nat. Genet. 1994; 8: 136-140Crossref PubMed Scopus (676) Google Scholar), whereas mice carrying the EA1-associated V408A mutation show stress-induced loss of motor coordination and a greater frequency and amplitude of spontaneous GABAergic IPSCs in cerebellar Purkinje cells (17Herson P.S. Virk M. Rustay N.R. Bond C.T. Crabbe J.C. Adelman J.P. Maylie J. Nat. Neurosci. 2003; 6: 378-383Crossref PubMed Scopus (124) Google Scholar). However, the effects of mutations in Kcna2 are unknown despite the fact that Kv1.1 and Kv1.2 are commonly present within the same tetramers (18Koch R.O. Wanner S.G. Koschak A. Hanner M. Schwarzer C. Kaczorowski G.J. Slaughter R.S. Garcia M.L. Knaus H.G. J. Biol. Chem. 1997; 272: 27577-27581Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar, 19Rhodes K.J. Strassle B.W. Monaghan M.M. Bekele-Arcuri Z. Matos M.F. Trimmer J.S. J. Neurosci. 1997; 17: 8246-8258Crossref PubMed Google Scholar). To this end, we characterized the in vivo and in vitro effects of a missense mutation (I402T; Pgu allele) in the S6 segment of the Kv1.2 α-subunit in mice. Here, we report that mice carrying the Pgu mutant allele of Kcna2 exhibit dominantly inherited chronic motor incoordination, due at least in part to an enhanced GABAergic inhibitory tone from basket cells onto Purkinje cells in the cerebellum.EXPERIMENTAL PROCEDURESMice and ENU MutagenesisMale C57BL/6J (B6) mice (The Jackson Laboratory) received three intraperitoneal injections of ENU (85 mg/kg) as previously described (20Xie G. Clapcote S.J. Nieman B.J. Tallerico T. Huang Y. Vukobradovic I. Cordes J. J.G. J.T. J.C. 2007; 6: PubMed Scopus Google Scholar). the ENU the to mice (The Jackson of this at for in or a for for A mouse an with and named Pingu This to and the through the same and screen as their the of the Pgu as and to for to the of the genetic and genetic of the To the of the Pgu mutation, mice in with the of the on the Pgu mutation to a specific a of nucleotide the and used to the of and Pgu mice at a of the Pgu mutation been to a of and used to the critical to in a total of mice. from a The used for and the have been described previously (20Xie G. Clapcote S.J. Nieman B.J. Tallerico T. Huang Y. Vukobradovic I. Cordes J. J.G. J.T. J.C. 2007; 6: PubMed Scopus Google gene of mouse Kcna2 from a of and and and and and from to the of mouse Kcna2 an the Kcna2 Pgu mutation a and and used for Pgu of the Pgu Kcna2 cDNA from the of a wild-type mouse and a for The of the for of the The of the wild-type Kcna2 and the of the E. M.D. M. S. M. M. 1994; PubMed Scopus Google from B. A. The To for the with and the of and from an mice on the at the 1 of the and for the transgenic that Kcna2 not of transgenic mice of from mice of the with The transgenic mouse to Pgu mutant mice with a from the cerebellum of transgenic mice and used to cDNA the The specific and for the transgenic that Kcna2 cDNA not be at the of with and with of containing in The and in the same at The in in at The at and in the containing and in for at The used at of from the cerebellum of mice to to and with and in with the of as to the and wild-type expressed as or Kv1.1 the transgenic mouse of from the cerebellum of mice at the of on an and at an of for The at a of The to with a of given three each with for The to for each mouse the three in each The on a to the of the in the the of the mice given the The for a mouse the and the of analyses the mice and whereas the mice the K. A. J. Neurosci. 1997; PubMed Scopus Google used to and the and to The of and in a A mouse the and the the with or The and from the the mouse its The in to this mouse to three with The of the three for each mouse intraperitoneal at a of in to a and at a of motor In the mice given three for three and on the for three In the mice as described previously and given of the and in CHO wild-type or I402T mutation Kcna2 cDNA as an wild-type Kcna1 cDNA as an The to the of the wild-type or I402T mutant cDNA CHO cells in with and at and on in 1 in a that the at the of In each of each respectively, and slices of mouse at a of a in containing and at a of in and The slices in the same at for which the slices for an at in a containing 1 and at a of in and and at action potential recordings slices with the and to synaptic in Purkinje cells, the potassium 1 and of the used but the of from and and slices to a with a at on an with and a Purkinje cell identified their large and large In the spontaneous Purkinje cell IPSCs at as in the of In the action at the action currents that with the potential at the at cells identified their and in the of the molecular within a of from the Purkinje cell The recordings that not action and to be from from the and in a with on an with and a cells, which and not in with cells, for whole cell used to determine the expression of enhanced The 1 and at a of whole cell current recordings in CHO cells, the and 1 at a of used as a to clamp current and and an clamp at and at and with and and and at are given as the and is within the large of the of the Kv1 potassium channel and is in the Kv1 of and in the channels of and M. Smith Yellen G. J. 1997; PubMed Scopus Google Scholar, Y. M. Yellen G. Neuron. 1997; 19: Full Text Full Text PDF PubMed Scopus Google Scholar, T. M. Nat. Biol. PubMed Scopus Google Scholar). The within the channel has been due to the fact that mutation at this to changes in channel and M. Smith Yellen G. J. 1997; PubMed Scopus Google Scholar, Y. M. Yellen G. Neuron. 1997; 19: Full Text Full Text PDF PubMed Scopus Google Scholar, K.J. J. 2002; PubMed Scopus Google Scholar). we that homomeric channels of Kv1.2(I402T) expressed in CHO cells, subtle changes in their and with wild-type homomeric Kv1.2 Kv1.2 I402T substitution the changes in Pgu mice in a of the and properties of the Kv1.2 α-subunit These the density and of Kv1.2 in the basket cell the stoichiometry of Kv1.2 α-subunit containing channels. The total expression of Kv1.1 and Kv1.2 α-subunit in and mice reduced in the cerebellum and respectively, which correlates with the of cerebellar ataxia This be the of low of the mutant as as of mutant subunits to within the and J. I. B. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, S.M. A. Biol. PubMed Scopus Google Scholar). This reduction in Kv1 have a dramatic effect on the of basket cell terminals to the of channels with the stoichiometry Trimmer J.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), which is of Kv1.1 and Kv1.2 This dramatic reduction in potassium channel the resting potential of the which have dramatic effects on release is to or in the E. Neuron. 2003; Full Text Full Text PDF PubMed Scopus Google and be in membrane potential that channel and Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). The reduction in the total amount of Kv1.1 and Kv1.2 α-subunit in the cerebellum is in line with the reduction in current density in CHO cells with This that CHO cells to potassium channels containing Kv1.2(I402T) the is to that the and of expression of potassium channels at the basket cell also be the of Kv1.2(I402T) in in the and density of potassium channels S. C. B. M. Dolly J.O. 1999; PubMed Scopus Google effect of the Kv1.2 I402T substitution in Pgu mice an increase in the frequency and the amplitude of Purkinje cell These from GABAergic and basket cells. Kv1.2 have not been in cells N.M. Averill S. Wilkin G.P. Dolly J.O. Priestley J.V. Eur. J. Neurosci. 1996; 8: 688-699Crossref PubMed Scopus (36) Google but are present in the of basket cells, with the in their are to excitability H. Kunkel D.D. Martin T.M. Schwartzkroin P.A. Tempel B.L. Nature. 1993; 365: 75-79Crossref PubMed Scopus (515) Google Scholar, 7Wang H. Kunkel D.D. Schwartzkroin P.A. Tempel B.L. J. Neurosci. 1994; 14: 4588-4599Crossref PubMed Google Scholar, 8McNamara N.M. Muniz Z.M. Wilkin G.P. Dolly J.O. Neuroscience. 1993; 57: 1039-1045Crossref PubMed Scopus (52) Google Scholar, 9McNamara N.M. Averill S. Wilkin G.P. Dolly J.O. Priestley J.V. Eur. J. Neurosci. 1996; 8: 688-699Crossref PubMed Scopus (36) Google Scholar). recordings in mice any of potassium currents in the presynaptic basket cell or the postsynaptic Purkinje cell B. J. Neurosci. PubMed Google Scholar, B. J. Neurosci. PubMed Google Scholar). have also shown that the Kv1.2 I402T substitution not the intrinsic spiking of basket cells. Kv1.2 subunits their effects at the basket cell I. J. 1999; PubMed Scopus Google are involved in action the presynaptic axon as as the resting membrane thereby controlling and These effectively the that a be and its a postsynaptic thereby the of this tonic inhibitory synaptic as in mice. with this of potassium currents in basket cell terminals has been shown to in a in the of the potassium in an increase in the frequency and amplitude of B. J. Neurosci. PubMed Google Scholar, B. J. Neurosci. PubMed Google Scholar). the of the be to the changes in Kv1 current due to the I402T substitution and make an for its role in the in Pgu in at a synaptic in the also the of that to postsynaptic output for in synaptic to be and in the to the of this cerebellar the increase in the synaptic of this tonic GABAergic be to the Purkinje cell with in the in vitro we that the Kv1.2 I402T substitution in a significant reduction in the frequency as as an of the of the action potential firing of Purkinje cells. The Kv1.2 I402T substitution in Pgu mice and in the output of Purkinje cells, which encodes important timing information for the of excitatory and inhibitory tonic which the subthreshold membrane potential at which the is the of the intrinsic conductances that the of the Purkinje the the inhibitory postsynaptic potential amplitude at the and the interspike prolongation is steep (11Jaeger D. De Schutter E. Bower J.M. J. Neurosci. 1997; 17: 91-106Crossref PubMed Google Scholar, 12Jaeger D. Bower J.M. J. Neurosci. 1999; 19: 6090-6101Crossref PubMed Google Scholar, 13Walter J.T. Alviña K. Womack M.D. Chevez C. Khodakhah K. Nat. Neurosci. 2006; 9: 389-397Crossref PubMed Scopus (319) Google the increase in the and of the of Purkinje cells in Pgu mice to effectively as the balance of invading the Purkinje also the of relevant excitatory and inhibitory synaptic inputs the inhibitory that on Purkinje cells, effectively the to cerebellum is involved in the regulation of the initiation and timing of movements and is important for maintaining balance and and as that the of associated with the Pgu mutation, which and the However, Kv1.2 is in cerebellar basket cell terminals and is important in cerebellar and is also expressed at throughout the and A. E. J. 1999; PubMed Google Scholar). and due to the of Kv1.2 channel and may also contribute to the motor To determine the to which the cerebellum is involved in the Pgu to be as cerebellar subunits are with Kv1.1 subunits in the cerebellar basket cell axon terminals and heteromeric channels H. Kunkel D.D. Martin T.M. Schwartzkroin P.A. Tempel B.L. Nature. 1993; 365: 75-79Crossref PubMed Scopus (515) Google Scholar, 7Wang H. Kunkel D.D. Schwartzkroin P.A. Tempel B.L. J. Neurosci. 1994; 14: 4588-4599Crossref PubMed Google Scholar, R.O. Wanner S.G. Koschak A. Hanner M. Schwarzer C. Kaczorowski G.J. Slaughter R.S. Garcia M.L. Knaus H.G. J. Biol. Chem. 1997; 272: 27577-27581Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar). Kv1.1 missense mutations human (16Browne D.L. Gancher S.T. Nutt J.G. Brunt E.R. Smith E.A. Kramer P. Litt M. Nat. Genet. 1994; 8: 136-140Crossref PubMed Scopus (676) Google Scholar). changes in cerebellar Purkinje cells in Pgu mice the changes described for the Kv1.1 V408A mutation mice (17Herson P.S. Virk M. Rustay N.R. Bond C.T. Crabbe J.C. Adelman J.P. Maylie J. Nat. Neurosci. 2003; 6: 378-383Crossref PubMed Scopus (124) Google Scholar), the are The Kv1.1 V408A mutation is whereas the Kv1.2 I402T mutation is Kv1.1 mice motor in the and the balance and their motor to be the of of the and whereas Kv1.2 mice chronic motor Kcna2 mice have greater and a Kcna1 mice R.S. J. A. Tempel B.L. J. 2007; PubMed Scopus Google Scholar, H. Schwartzkroin P.A. A. Tempel B.L. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). These suggest that Kv1.2 subunits may play an not role Kv1.1 in the of cerebellar motor and whereas Kv1.1 subunits are important Kv1.2 This is with the strong of Kv1.2 expression in the R.S. J. A. Tempel B.L. J. 2007; PubMed Scopus Google Scholar, H. Trimmer J.S. J.P. D. J.M. J. 1996; PubMed Scopus Google and a strong expression of Kv1.1 Tempel B.L. J. Neurosci. PubMed Google Kv1.2 I402T chronic motor incoordination, whereas Kv1.2 mice to have motor despite a reduction of Kv1.2 in the brain R.S. J. A. Tempel B.L. J. 2007; PubMed Scopus Google Scholar). Kv1.2 I402T motor incoordination from whereas Kv1.2 mice not show R.S. J. A. Tempel B.L. J. 2007; PubMed Scopus Google Scholar). This is to the effects of the Kv1.1 V408A mutation in the mouse (17Herson P.S. Virk M. Rustay N.R. Bond C.T. Crabbe J.C. Adelman J.P. Maylie J. Nat. Neurosci. 2003; 6: 378-383Crossref PubMed Scopus (124) Google Scholar). The of the Kv1.1 V408A mutation the of this to the of Kv1 channels in The of Kv1.2 Pgu provide an mouse for in vivo of this voltage-gated potassium and any as as potential for IntroductionVoltage-gated potassium channels play a key role in neuronal excitability and plasticity and are critical in establishing resting membrane potential and firing thresholds, repolarizing action potentials, and limiting excitability (1Hille B. Ionic Channels of Excitable Membranes. Sinauer, Sunderland, MA2001Google Scholar). Channels are unevenly distributed throughout the brain as a whole and also within individual neurons (2Trimmer J.S. Proc. Natl. Acad. Sci. U.S.A. 1991; 88: 10764-10768Crossref PubMed Scopus (213) Google Scholar, 3Drewe J.A. Verma S. Frech G. Joho R.H. J. Neurosci. 1992; 12: 538-548Crossref PubMed Google Scholar, 4Hwang P.M. Glatt C.E. Bredt D.S. Yellen G. Snyder S.H. Neuron. 1992; 8: 473-481Abstract Full Text PDF PubMed Scopus (103) Google Scholar, 5Hwang P.M. Fotuhi M. Bredt D.S. Cunningham A.M. Snyder S.H. J. Neurosci. 1993; 13: 1569-1576Crossref PubMed Google Scholar, 6Wang H. Kunkel D.D. Martin T.M. Schwartzkroin P.A. Tempel B.L. Nature. 1993; 365: 75-79Crossref PubMed Scopus (515) Google Scholar, 7Wang H. Kunkel D.D. Schwartzkroin P.A. Tempel B.L. J. Neurosci. 1994; 14: 4588-4599Crossref PubMed Google Scholar, 8McNamara N.M. Muniz Z.M. Wilkin G.P. Dolly J.O. Neuroscience. 1993; 57: 1039-1045Crossref PubMed Scopus (52) Google Scholar, 9McNamara N.M. Averill S. Wilkin G.P. Dolly J.O. Priestley J.V. Eur. J. Neurosci. 1996; 8: 688-699Crossref PubMed Scopus (36) Google Scholar, 10Sheng M. Tsaur M.L. Jan Y.N. Jan L.Y. J. Neurosci. 1994; 14: 2408-2417Crossref PubMed Google Scholar). Therefore, the particular utility of any given channel depends not only on its specific channel properties and stoichiometry but also on its particular localization and density within a cell or cellular compartment. In the cerebellum, the genes Kcna1 and Kcna2 encode the voltage-gated potassium channel subunits Kv1.1 and Kv1.2, respectively, which contribute to the low voltage-activated potassium current IKv1 and are coexpressed in the presynaptic GABAergic pinceaus of spontaneously firing basket cell interneurons that provide a strong inhibitory input to Purkinje cells (5Hwang P.M. Fotuhi M. Bredt D.S. Cunningham A.M. Snyder S.H. J. Neurosci. 1993; 13: 1569-1576Crossref PubMed Google Scholar, 6Wang H. Kunkel D.D. Martin T.M. Schwartzkroin P.A. Tempel B.L. Nature. 1993; 365: 75-79Crossref PubMed Scopus (515) Google Scholar, 7Wang H. Kunkel D.D. Schwartzkroin P.A. Tempel B.L. J. Neurosci. 1994; 14: 4588-4599Crossref PubMed Google Scholar, 8McNamara N.M. Muniz Z.M. Wilkin G.P. Dolly J.O. Neuroscience. 1993; 57: 1039-1045Crossref PubMed Scopus (52) Google Scholar, 9McNamara N.M. Averill S. Wilkin G.P. Dolly J.O. Priestley J.V. Eur. J. Neurosci. 1996; 8: 688-699Crossref PubMed Scopus (36) Google Scholar). The shunting effect of this inhibitory conductance has been shown through modeling to have a steep correlation with the prolongation of Purkinje cell interspike intervals in vitro (11Jaeger D. De Schutter E. Bower J.M. J. Neurosci. 1997; 17: 91-106Crossref PubMed Google Scholar, 12Jaeger D. Bower J.M. J. Neurosci. 1999; 19: 6090-6101Crossref PubMed Google Scholar, 13Walter J.T. Alviña K. Womack M.D. Chevez C. Khodakhah K. Nat. Neurosci. 2006; 9: 389-397Crossref PubMed Scopus (319) Google Scholar).The cerebellum is involved in the regulation of the initiation and timing of movements and is important for maintaining balance and posture (14Morton S.M. Bastian A.J. Cerebellum. 2007; 6: 79-86Crossref PubMed Scopus (131) Google Scholar). At the core of the cerebellar computational circuitry, the spontaneously spiking Purkinje cells integrate cerebral cortical and sensory, excitatory and inhibitory inputs encoding relevant information in their action potential discharge and communicate the information to the deep cerebellar nuclei for the final output of the cerebellum (15Bower J.M. Ann. N. Y. Acad. Sci. 2002; 978: 135-155Crossref PubMed Scopus (92) Google Scholar). The total synaptic conductance invading a Purkinje cell effectively functions to clamp the subthreshold membrane voltage, thereby controlling the state of the active conductances that determine each Purkinje cell intrinsic pacemaking activity, which in turn shapes the tonic GABAergic inhibition targeted to the deep cerebellar nuclei (11Jaeger D. De Schutter E. Bower J.M. J. Neurosci. 1997; 17: 91-106Crossref PubMed Google Scholar).Missense mutations of Kcna1 are associated with type 1 episodic ataxia (EA1) 3The abbreviations used are: EA1type 1 episodic ataxiaIPSCinhibitory postsynaptic currentsIPSCspontaneous IPSCmIPSCminiature IPSCATZacetazolamideGABAγ-aminobutyric acidNSEneuron-specific enolaseSNPsingle nucleotide polymorphismTTXtetrodotoxinpFpicofaradsNBQX2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dioneMbmegabase. (16Browne D.L. Gancher S.T. Nutt J.G. Brunt E.R. Smith E.A. Kramer P. Litt M. Nat. Genet. 1994; 8: 136-140Crossref PubMed Scopus (676) Google Scholar), whereas mice carrying the EA1-associated V408A mutation show stress-induced loss of motor coordination and a greater frequency and amplitude of spontaneous GABAergic IPSCs in cerebellar Purkinje cells (17Herson P.S. Virk M. Rustay N.R. Bond C.T. Crabbe J.C. Adelman J.P. Maylie J. Nat. Neurosci. 2003; 6: 378-383Crossref PubMed Scopus (124) Google Scholar). However, the effects of mutations in Kcna2 are unknown despite the fact that Kv1.1 and Kv1.2 are commonly present within the same tetramers (18Koch R.O. Wanner S.G. Koschak A. Hanner M. Schwarzer C. Kaczorowski G.J. Slaughter R.S. Garcia M.L. Knaus H.G. J. Biol. Chem. 1997; 272: 27577-27581Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar, 19Rhodes K.J. Strassle B.W. Monaghan M.M. Bekele-Arcuri Z. Matos M.F. Trimmer J.S. J. Neurosci. 1997; 17: 8246-8258Crossref PubMed Google Scholar). To this end, we characterized the in vivo and in vitro effects of a missense mutation (I402T; Pgu allele) in the S6 segment of the Kv1.2 α-subunit in mice. Here, we report that mice carrying the Pgu mutant allele of Kcna2 exhibit dominantly inherited chronic motor incoordination, due at least in part to an enhanced GABAergic inhibitory tone from basket cells onto Purkinje cells in the

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.