Ectopic HCN4 expression drives mTOR-dependent epilepsy in mice

The causative link between focal cortical malformations (FCMs) and epilepsy is well accepted, especially among patients with focal cortical dysplasia type II (FCDII) and tuberous sclerosis complex (TSC). However, the mechanisms underlying seizures remain unclear. Using a mouse model of TSC- and FCDII-associated FCM, we showed that FCM neurons were responsible for seizure activity via their unexpected abnormal expression of the hyperpolarization-activated cyclic nucleotide–gated potassium channel isoform 4 (HCN4), which is normally not present in cortical pyramidal neurons after birth. Increasing intracellular cAMP concentrations, which preferentially affects HCN4 gating relative to the other isoforms, drove repetitive firing of FCM neurons but not control pyramidal neurons. Ectopic HCN4 expression was dependent on the mechanistic target of rapamycin (mTOR), preceded the onset of seizures, and was also found in diseased neurons in tissue resected from patients with TSC and FCDII. Last, blocking HCN4 channel activity in FCM neurons prevented epilepsy in the mouse model. These findings suggest that HCN4 play a main role in seizure and identify a cAMP-dependent seizure mechanism in TSC and FCDII. Furthermore, the unique expression of HCN4 exclusively in FCM neurons suggests that gene therapy targeting HCN4 might be effective in reducing seizures in FCDII or TSC.

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Ectopic HCN4 expression drives mTOR-dependent epilepsy

10.1101/853820 ◽

2019 ◽

Author(s):

Lawrence S. Hsieh ◽

John H. Wen ◽

Lena H. Nguyen ◽

Longbo Zhang ◽

Juan Torres-Reveron ◽

...

Keyword(s):

Gene Therapy ◽

Tuberous Sclerosis ◽

Tuberous Sclerosis Complex ◽

Pyramidal Neurons ◽

Focal Cortical Dysplasia ◽

Ectopic Expression ◽

Cortical Dysplasia ◽

Repetitive Firing ◽

Intracellular Camp ◽

Cortical Pyramidal Neurons

AbstractThe causative link between focal cortical malformations (FCM) and epilepsy is well-accepted, especially among patients with focal cortical dysplasia type II (FCDII) and tuberous sclerosis complex (TSC). However, the mechanisms underlying seizures remain unclear. Using a mouse model of TSC- and FCDII-associated FCM, we show that FCM neurons are responsible for seizure activity via their unexpected abnormal expression of the hyperpolarization-activated cyclic nucleotide-gated potassium channel isoform 4 (HCN4), which is normally not present in cortical pyramidal neurons after birth. Increasing intracellular cAMP levels, which preferentially affects HCN4 gating relative to the other isoforms, drove repetitive firing of FCM neurons but not that of control pyramidal neurons. Ectopic HCN4 expression was mTOR-dependent, preceded the onset of seizures, and was also found in diseased neurons in tissue resected for epilepsy treatment from TSC and FCDII patients. Finally, blocking HCN4 channel activity in FCM neurons prevented epilepsy in mice. These findings that demonstrate HCN4 acquisition as seizure-genic, identify a novel cAMP-dependent seizure mechanism in TSC and FCDII. Furthermore, the unique expression of HCN4 exclusively in FCM neurons provides opportunities for using HCN4 as a gene therapy target to treat epilepsy in individuals with FCDII or TSC.One Sentence SummaryOur data provide a novel cAMP-dependent mechanism of seizure initiation in focal cortical dysplasia and tuberous sclerosis complex due to the unexpected ectopic expression of HCN4 channels only in diseased neurons. HCN4 channels are thus promising candidates for gene therapy to treat epilepsy generated by mTOR-driven focal malformations.

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Calcium dysregulation and compensation in cortical pyramidal neurons of the R6/2 mouse model of Huntington’s disease

Journal of Neurophysiology ◽

10.1152/jn.00181.2021 ◽

2021 ◽

Vol 126 (4) ◽

pp. 1159-1171

Author(s):

Katerina D. Oikonomou ◽

Elissa J. Donzis ◽

Minh T. N. Bui ◽

Carlos Cepeda ◽

Michael S. Levine

Keyword(s):

Mouse Model ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Pyramidal Neurons ◽

Calcium Influx ◽

Calcium Transient ◽

Two Photon Microscopy ◽

Decay Times ◽

Cortical Pyramidal Neurons ◽

Receptor Blockers

We used two-photon microscopy to examine calcium influx induced by action potentials in cortical pyramidal neurons from a mouse model of Huntington’s disease (HD), the R6/2. The amplitude of somatic calcium transients was reduced in R6/2 mice compared with controls. This reduction was compensated by increased decay times, which could lead to reduced calcium buffering capacity. L-type calcium channel and ryanodine receptor blockers reduced calcium transient area in HD neurons, suggesting new therapeutic avenues.

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Protein Kinase C Controls the Excitability of Cortical Pyramidal Neurons by Regulating Kv2.2 Channel Activity

Neuroscience Bulletin ◽

10.1007/s12264-021-00773-x ◽

2021 ◽

Author(s):

Zhaoyang Li ◽

Wenhao Dong ◽

Xinyuan Zhang ◽

Jun-Mei Lu ◽

Yan-Ai Mei ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Pyramidal Neurons ◽

Channel Activity ◽

Kinase C ◽

Cortical Pyramidal Neurons

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Modified excitability and persistent sodium current amplitude in cortical pyramidal neurons from a mouse model of Amyotrophic Lateral Sclerosis

IBRO Reports ◽

10.1016/j.ibror.2019.07.1535 ◽

2019 ◽

Vol 6 ◽

pp. S489

Author(s):

Cristina Zona ◽

Luana Saba ◽

Silvia Caioli

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Mouse Model ◽

Pyramidal Neurons ◽

Sodium Current ◽

Current Amplitude ◽

Persistent Sodium Current ◽

Cortical Pyramidal Neurons ◽

Lateral Sclerosis

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Altered excitatory and inhibitory inputs to striatal medium-sized spiny neurons and cortical pyramidal neurons in the Q175 mouse model of Huntington's disease

Journal of Neurophysiology ◽

10.1152/jn.01056.2014 ◽

2015 ◽

Vol 113 (7) ◽

pp. 2953-2966 ◽

Cited By ~ 40

Author(s):

Tim Indersmitten ◽

Conny H. Tran ◽

Carlos Cepeda ◽

Michael S. Levine

Keyword(s):

Mouse Model ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Primary Motor Cortex ◽

Pyramidal Neurons ◽

Membrane Properties ◽

Postsynaptic Currents ◽

Spiny Neurons ◽

Cortical Pyramidal Neurons ◽

Intrinsic Membrane Properties

The Q175 knockin mouse model of Huntington's disease (HD) carries a CAG trinucleotide expansion of the human mutant huntingtin allele in its native mouse genomic context and recapitulates the genotype more closely than transgenic models. In this study we examined the progression of changes in intrinsic membrane properties and excitatory and inhibitory synaptic transmission, using whole cell patch-clamp recordings of medium-sized spiny neurons (MSNs) in the dorsolateral striatum and cortical pyramidal neurons (CPNs) in layers 2/3 of the primary motor cortex in brain slices from heterozygous (Q175+/−) and homozygous (Q175+/+) mice. Input resistance in MSNs from Q175+/+ and Q175+/− mice was significantly increased compared with wild-type (WT) littermates beginning at 2 mo. Furthermore, the frequency of spontaneous and miniature excitatory postsynaptic currents (EPSCs) was significantly reduced in MSNs from Q175+/+ and Q175+/− mice compared with WTs beginning at 7 mo. In contrast, the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) and IPSC-to-EPSC ratios were increased in MSNs from Q175+/+ mice beginning at 2 mo. Morphologically, significant decreases in spine density of MSNs from Q175+/− and Q175+/+ mice occurred at 7 and 12 mo. In CPNs, sIPSC frequencies and IPSC-to-EPSC ratios were significantly increased in Q175+/− mice compared with WTs at 12 mo. There were no changes in intrinsic membrane properties or morphology. In summary, we show a number of alterations in electrophysiological and morphological properties of MSNs in Q175 mice that are similar to other HD mouse models. However, unlike other models, CPN inhibitory activity is increased in Q175+/− mice, indicating reduced cortical excitability.

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Phospho-Tau Accumulation and Structural Alterations of the Golgi Apparatus of Cortical Pyramidal Neurons in the P301S Tauopathy Mouse Model

Journal of Alzheimer s Disease ◽

10.3233/jad-170332 ◽

2017 ◽

Vol 60 (2) ◽

pp. 651-661 ◽

Cited By ~ 6

Author(s):

Alejandro Antón-Fernández ◽

Jesús Merchán-Rubira ◽

Jesús Avila ◽

Félix Hernández ◽

Javier DeFelipe ◽

...

Keyword(s):

Golgi Apparatus ◽

Mouse Model ◽

Pyramidal Neurons ◽

Structural Alterations ◽

Cortical Pyramidal Neurons

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Genetic disruption of ankyrin-G in adult mouse forebrain causes cortical synapse alteration and behavior reminiscent of bipolar disorder

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1700689114 ◽

2017 ◽

Vol 114 (39) ◽

pp. 10479-10484 ◽

Cited By ~ 24

Author(s):

Shanshan Zhu ◽

Zachary A. Cordner ◽

Jiali Xiong ◽

Chi-Tso Chiu ◽

Arabiye Artola ◽

...

Keyword(s):

Bipolar Disorder ◽

Mouse Model ◽

Pyramidal Neurons ◽

Association Studies ◽

Behavioral Changes ◽

Genome Wide Association Studies ◽

Ankyrin G ◽

Genome Wide ◽

Cortical Pyramidal Neurons ◽

And Behavior

Genome-wide association studies have implicated the ANK3 locus in bipolar disorder, a major human psychotic illness. ANK3 encodes ankyrin-G, which organizes the neuronal axon initial segment (AIS). We generated a mouse model with conditional disruption of ANK3 in pyramidal neurons of the adult forebrain (Ank-G cKO). This resulted in the expected loss of pyramidal neuron AIS voltage-gated sodium and potassium channels. There was also dramatic loss of markers of afferent GABAergic cartridge synapses, resembling the cortical microcircuitry changes in brains from psychotic patients, and suggesting disinhibition. Expression of c-fos was increased in cortical pyramidal neurons, consistent with increased neuronal activity due to disinhibition. The mice showed robust behavioral phenotypes reminiscent of aspects of human mania, ameliorated by antimania drugs lithium and valproate. Repeated social defeat stress resulted in repeated episodes of dramatic behavioral changes from hyperactivity to “depression-like” behavior, suggestive of some aspects of human bipolar disorder. Overall, we suggest that this Ank-G cKO mouse model recapitulates some of the core features of human bipolar disorder and indicates that cortical microcircuitry alterations during adulthood may be involved in pathogenesis. The model may be useful for studying disease pathophysiology and for developing experimental therapeutics.

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Reversal of dendritic phenotypes in 16p11.2 microduplication mouse model neurons by pharmacological targeting of a network hub

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1607014113 ◽

2016 ◽

Vol 113 (30) ◽

pp. 8520-8525 ◽

Cited By ~ 30

Author(s):

Katherine D. Blizinsky ◽

Blanca Diaz-Castro ◽

Marc P. Forrest ◽

Britta Schürmann ◽

Anthony P. Bach ◽

...

Keyword(s):

Mental Disorders ◽

Mouse Model ◽

Gene Networks ◽

Pyramidal Neurons ◽

Genetic Alterations ◽

Copy Number Variations ◽

Driver Gene ◽

Wide Range ◽

Cortical Pyramidal Neurons ◽

Cellular Phenotypes

The architecture of dendritic arbors contributes to neuronal connectivity in the brain. Conversely, abnormalities in dendrites have been reported in multiple mental disorders and are thought to contribute to pathogenesis. Rare copy number variations (CNVs) are genetic alterations that are associated with a wide range of mental disorders and are highly penetrant. The 16p11.2 microduplication is one of the CNVs most strongly associated with schizophrenia and autism, spanning multiple genes possibly involved in synaptic neurotransmission. However, disease-relevant cellular phenotypes of 16p11.2 microduplication and the driver gene(s) remain to be identified. We found increased dendritic arborization in isolated cortical pyramidal neurons from a mouse model of 16p11.2 duplication (dp/+). Network analysis identified MAPK3, which encodes ERK1 MAP kinase, as the most topologically important hub in protein–protein interaction networks within the 16p11.2 region and broader gene networks of schizophrenia-associated CNVs. Pharmacological targeting of ERK reversed dendritic alterations associated with dp/+ neurons, outlining a strategy for the analysis and reversal of cellular phenotypes in CNV-related psychiatric disorders.

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