Abolishing cAMP sensitivity in HCN2 pacemaker channels induces generalized seizures
Verena Hammelmann, Marc Sebastian Stieglitz, Henrik Hülle, Karim Le Meur, Jennifer Kass, Manuela Brümmer, Christian Gruner, René Dominik Rötzer, Stefanie Fenske, Jana Hartmann, Benedikt Zott, Anita Lüthi, Saskia Spahn, Markus Moser, Dirk Isbrandt, Andreas Ludwig, Arthur Konnerth, Christian Wahl-Schott, Martin Biel
Verena Hammelmann, Marc Sebastian Stieglitz, Henrik Hülle, Karim Le Meur, Jennifer Kass, Manuela Brümmer, Christian Gruner, René Dominik Rötzer, Stefanie Fenske, Jana Hartmann, Benedikt Zott, Anita Lüthi, Saskia Spahn, Markus Moser, Dirk Isbrandt, Andreas Ludwig, Arthur Konnerth, Christian Wahl-Schott, Martin Biel
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Research Article Neuroscience

Abolishing cAMP sensitivity in HCN2 pacemaker channels induces generalized seizures

Abstract

Hyperpolarization-activated cyclic nucleotide–gated (HCN) channels are dually gated channels that are operated by voltage and by neurotransmitters via the cAMP system. cAMP-dependent HCN regulation has been proposed to play a key role in regulating circuit behavior in the thalamus. By analyzing a knockin mouse model (HCN2EA), in which binding of cAMP to HCN2 was abolished by 2 amino acid exchanges (R591E, T592A), we found that cAMP gating of HCN2 is essential for regulating the transition between the burst and tonic modes of firing in thalamic dorsal-lateral geniculate (dLGN) and ventrobasal (VB) nuclei. HCN2EA mice display impaired visual learning, generalized seizures of thalamic origin, and altered NREM sleep properties. VB-specific deletion of HCN2, but not of HCN4, also induced these generalized seizures of the absence type, corroborating a key role of HCN2 in this particular nucleus for controlling consciousness. Together, our data define distinct pathological phenotypes resulting from the loss of cAMP-mediated gating of a neuronal HCN channel.

Authors

Verena Hammelmann, Marc Sebastian Stieglitz, Henrik Hülle, Karim Le Meur, Jennifer Kass, Manuela Brümmer, Christian Gruner, René Dominik Rötzer, Stefanie Fenske, Jana Hartmann, Benedikt Zott, Anita Lüthi, Saskia Spahn, Markus Moser, Dirk Isbrandt, Andreas Ludwig, Arthur Konnerth, Christian Wahl-Schott, Martin Biel

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Figure 6

Analysis of neuronal network activity in the thalamic VB region.

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Analysis of neuronal network activity in the thalamic VB region. (A) Fir...
(A) Firing properties of WT and HCN2EA TC neurons from the VB region. Shown are action potentials elicited by 300-ms depolarizing current pulses at resting membrane potential of WT and HCN2EA TC neurons under control conditions (–cAMP) and in the presence of 1 μM cAMP. Unlike WT neurons, HCN2EA neurons fail to switch from burst to tonic firing in the presence of cAMP within the current range from 50–200 pA. The insets show representative examples of tonic (I) and burst (II) firing activity induced by injecting 150 pA in a WT and HCN2EA neuron, respectively. Traces are representatives of measurements shown in B. (B) Frequency of action potential generation as a function of the injected current. HCN2EA: solid blue line, –cAMP (n = 6); dashed blue line, +cAMP (n = 6). WT: solid gray line, –cAMP (n = 4); dashed gray line, +cAMP (n = 5). (C) Resting membrane potential (RMP) of TC neurons from the VB of HCN2EA (blue squares, –cAMP [n = 11]; blue circles, +cAMP [n = 7]) and WT (gray squares, –cAMP [n = 13]; gray circles, +cAMP [n = 10]).**P < 0.01 (P = 0.0083 [EA], P = 0.0013 [WT]) by Mann-Whitney test. (D) Voltage-sag ratios of TCs in response to injected current. HCN2EA (blue squares, –cAMP [n = 11]; blue circles, +cAMP [n = 7]); WT (gray squares, –cAMP [n = 13]; gray circles, +cAMP [n = 10]). (E) Original traces of spontaneous activity of individual thalamic neurons visualized using 2-photon calcium imaging. The raster plots under the traces (gray) indicate the detected peaks. All active cells from WT mice show irregular transients (left, n = 74), whereas more than one-third of the active cells from HCN2EA mice show oscillatory transients (right, n = 25). (F) Autocorrelograms of the traces shown in E. Gray, original autocorrelation function (ACF); black, smoothed ACF; red, cubic spline interpolation of the smoothed ACF.