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Principal Investigator: Dax A Hoffman
Organization: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
Fiscal Year: 2024
Award: $2,312,037
Funding agency: Eunice Kennedy Shriver National Institute of Child Health and Human Development
Kv4.2 is an activity-dependent Ube3A substrate and contributes to synaptic plasticity and cognitive flexibility in Angelman syndrome
Angelman syndrome (AS) is a severe neurodevelopmental disorder affecting 1 in 20,000 people, caused by loss of function of imprinted genes on chromosome 15q11–13 or mutations in Ube3A. Ube3A is expressed exclusively from the maternal allele in hippocampal neurons and cerebellar Purkinje cells. Loss of Ube3A function leads to accumulation of target proteins, disrupting neuronal function. A TAP-MS screen identified Ube3A as a Kv4.2 binding protein. Follow-up studies by Dr. Jiahua Hu confirmed activity-dependent Kv4.2–Ube3A interaction, showing Ube3A ubiquitinates Kv4.2 at residue K103, which is required for activity-induced Kv4.2 degradation.
In an AS mouse model, Kv4.2 protein levels and K+ currents are elevated in the hippocampus. Seizure-induced Kv4.2 degradation, which normally requires Ube3A, is absent in AS mice. Ube3A-mediated Kv4.2 ubiquitination is significantly reduced in AS hippocampi, further supporting the role of Ube3A in Kv4.2 degradation. Additionally, studies showed that seizure-induced Kv4.2 degradation occurs on DPP6-containing Kv4.2 complexes, requiring Kv4.2 phosphorylation at the T602/7 Pin1 site.
Patch clamp studies by Dr. Cole Malloy revealed deficits in mEPSC frequency and spike-timing-dependent LTP in AS mice, which were rescued by crossing AS mice with conditional Kv4.2 KO (Kv4.2cKO) mice. Behavioral tests showed that some locomotion, nesting, and learning impairments in AS mice were also partially rescued in AS/Kv4.2cKO mice. In learning and memory tests, AS mice showed impairments in initial learning and reversal learning in an operant reversal test. However, the deficits in AS mice in reversal learning can be rescued by DKO mice. These findings reveal a novel Ube3A downstream pathway regulating plasticity and cognitive behaviors, and provide potential targets for the treatment of AS.
Kv4.2 complex regulation and its role in cognitive flexibility
To address the role of the p38-Pin1-Kv4.2 pathway in neuronal excitability and circuit function, we developed a mutant knock-in mouse model with a Thr607 to Ala substitution at the activity-induced p38 phosphorylation site (T607 to A607; Kv4.2TA). We have found that Kv4.2TA mice exhibit normal initial learning and memory in the Morris Water Maze and Lever Press, two tests of hippocampal-dependent learning and memory. However, they exhibited better 'reversal' learning in both tests than did WT mice. This improvement in reversal learning is indicative of an enhancement in cognitive flexibility. Dr. Malloy is investigating the mechanisms behind enhanced cognitive flexibility in Kv4.2TA mice, the first mouse model with this phenotype. Focusing on synaptic differences between Kv4.2TA and WT mice, patch clamp electrophysiology in hippocampal CA1 pyramidal cells showed that Kv4.2TA mice have similar basal synaptic transmission and preserved long-term plasticity. However, they exhibited a significant enhancement in the reversal of spike-timing dependent long-term potentiation with low-frequency stimulation (LFS), suggesting a synapse state-dependent difference in synaptic plasticity due to altered Kv4.2 complex regulation.
Pharmacological manipulations during LFS revealed distinct mechanisms driving this metaplasticity. The NMDA antagonist 5-AP, which fully blocks depotentiation in WT mice, only partially blocks it (~40%) in Kv4.2TA mice, indicating an additional mechanism in Kv4.2TA mice. The hypothesis is that altered metabotropic glutamate receptor (mGluR) signaling, specifically mGluR5, underlies this enhancement. Co-application of the mGluR5 antagonist MTEP with 5-AP fully rescues the depotentiation in Kv4.2TA mice, bringing it to WT levels, while MTEP alone fully prevents depotentiation in Kv4.2TA mice and only partially affects WT mice. This suggests depotentiation in Kv4.2TA mice is primarily driven by mGluR5, while in WT mice, NMDA receptors are more dominant.
In summary, this study uncovers a novel metaplasticity mechanism in Kv4.2TA mice linked to cognitive flexibility, with implications for therapeutic strategies targeting neurodevelopmental disorders with cognitive flexibility impairments. It reveals a shift in the molecular drivers of depotentiation between Kv4.2TA and WT mice, likely due to impaired Kv4.2 complex trafficking during synaptic activity.
Preso1 regulation of Kv4.2 channels in the hippocampus
Intellectual disability (ID) affects 1-3% of the population and is marked by learning and adaptive behavior impairments. While the cause is unclear, mutations in the Preso1 (FRMPD4) gene, a neuronal post-synaptic scaffold protein, have been linked to X-linked ID. Preso1 is a neuronal post-synaptic scaffold protein that regulates hippocampal excitatory synaptic transmission and spine development. We found Preso1 regulates Kv4.2 channels in the hippocampus. First, we show Preso1 directly binds to Kv4.2. In patch recordings, Dr. Welch found that knocking out Preso1 reduced the transient A-type potassium current (IA) by ~30% in CA1 pyramidal neurons compared to controls. This reduction in Kv4.2 channels led to increased hippocampal excitability, with KO mice showing higher firing rates, a more depolarized action potential threshold, higher action potential amplitude, lower rheobase, and shorter latency to fire. Synaptic properties in KO mice showed no difference in paired-pulse ratio, but a significant deficit in spike-timing dependent LTP at CA3-CA1 synapses compared to wild-type mice. Ongoing research is examining basal synaptic transmission. These findings identify Kv4.2 as a novel target of Preso1, showing its disruption affects hippocampal excitability and synaptic plasticity in Preso1 KO mice.
Seizure analysis in aging DPP6-KO mouse related to Alzheimer’s disease/dementia
We discovered novel roles for the voltage-gated potassium channel auxiliary subunit DPP6 (Dipeptidyl Peptidase-Like 6) in neuronal development, learning, memory, and its connection to Alzheimer's disease (AD)/dementia. In aging DPP6-KO mice, amyloid-β (Aβ)-associated structures were found in the hippocampal area CA1, likely from degenerating presynaptic terminals, with a higher prevalence compared to WT mice. These mice also showed increased Aβ, tau pathologies, neuroinflammation, and sleep disturbances.
AD patients have an eight-fold higher risk of epileptic seizures. We examined seizures in DPP6-KO mice, detecting EEG spike-wave discharges, indicative of nonconvulsive seizures. Using HD-X02 telemetry, data from 12-month-old DPP6-KO mice showed a higher prevalence of spike-wave discharges and nonconvulsive seizures compared to WT controls. They also had longer spike train durations and more high amplitude single spikes. However, 3-month-old DPP6-KO mice did not exhibit significant increases in seizures compared to WT littermates. These findings suggest age-dependent seizure activity and high amplitude spikes in DPP6-KO mice, reinforcing DPP6's role in Alzheimer's/dementia.
Terms: <AD dementia><ASD><Action Potentials><Adaptive Behaviors><Address><Affect><Aging><Alleles><Allelomorphs><Alzheimer Type Dementia><Alzheimer beta-Protein><Alzheimer disease dementia><Alzheimer sclerosis><Alzheimer syndrome><Alzheimer's><Alzheimer's Amyloid beta-Protein><Alzheimer's Disease><Alzheimer's amyloid><Alzheimer's disease patient><Alzheimer's patient><Alzheimers Dementia><Amentia><Ammon Horn><Amyloid Alzheimer's Dementia Amyloid Protein><Amyloid Beta-Peptide><Amyloid Protein A4><Amyloid beta-Protein><Amyloid β><Amyloid β-Peptide><Amyloid β-Protein><Angelman Syndrome><Area><Autism><Autistic Disorder><Automobile Driving><Axon Terminals><Aβ><Behavior><Binding><Binding Proteins><Brain><Brain Nervous System><Brain region><CNS Diseases><CNS Nervous System><CNS disorder><CSAID-Binding Protein 1><CSAID-Binding Protein 2><CSBP2><Central Nervous System><Central Nervous System Diseases><Central Nervous System Disorders><Chromosomes><Cognitive><Complex><Cornu Ammonis><Cytokine-Suppressive Antiinflammatory Drug-Binding Protein 1><Cytokine-Suppressive Antiinflammatory Drug-Binding protein 2><Data><Dementia><Dendrites><Depotentiation><Development><Dipeptidyl Aminopeptidases><Dipeptidyl Peptidases><Dipeptidylpeptide Hydrolases><E6AP><EEG><Early Infantile Autism><Electroencephalogram><Electroencephalography><Electrophysiology><Electrophysiology (science)><Emotions><Encephalon><Epilepsy><Epileptic Seizures><Epileptics><Escalante syndrome><Exhibits><Fire - disasters><Fires><Follow-Up Studies><Followup Studies><Fragile X><Fragile X Syndrome><Frequencies><Genes><Genetic Alteration><Genetic Change><Genetic defect><Glutamate Receptor><Happy Puppet Syndrome><High Prevalence><Hippocampus><Homosynaptic Depression><Human><Impairment><Individual><Infantile Autism><Intellectual disability><Intellectual functioning disability><Intellectual limitation><Ion Channel><Ionic Channels><K channel><K element><KCND2 channel><KI mice><KO mice><Kanner's Syndrome><Knock-in Mouse><Knock-out><Knock-out Mice><Knockout><Knockout Mice><Knowledge><Kv4.2 channel><Learning><Ligand Binding Protein><Ligand Binding Protein Gene><Link><Locomotion><Long-Term Potentiation><Longterm Potentiation><MAPK14><MAPK14 Mitogen-Activated Protein Kinase><MAPK14 gene><MT-bound tau><Martin-Bell Syndrome><Martin-Bell-Renpenning syndrome><Mediating><Membrane Channels><Memory><Metabotropic Glutamate Receptors><Mice><Mice Mammals><Mitogen-Activated Protein Kinase 14><Modern Man><Molecular><Molecular Interaction><Murine><Mus><Mutation><Mxi2><N Methyl D aspartic Acid><N methyl D aspartate><N-Methyl-D-Aspartate Receptors><N-Methyl-D-aspartate><N-Methylaspartate><N-Methylaspartate Receptors><NMDA><NMDA Receptor-Ionophore Complex><NMDA Receptors><Nerve Cells><Nerve Unit><Neural Cell><Neural Transmission><Neuraxis><Neurocyte><Neurodevelopmental Disorder><Neurological Development Disorder><Neurons><Neurophysiology / Electrophysiology><Null Mouse><Pathology><Pathway interactions><Persons><Phenotype><Phosphorylation><Phosphorylation Site><Physiologic pulse><Population><Potassium><Potassium Channel><Potassium Ion Channels><Presynaptic Nerve Endings><Presynaptic Terminals><Primary Senile Degenerative Dementia><Process><Property><Protein Binding><Protein Phosphorylation><Proteins><Pulse><Puppet Children><Purkinje Cells><Purkinje's Corpuscles><Pyramidal Cells><Pyramidal neuron><Receptor Signaling><Regulation><Renpenning syndrome 2><Research><Reversal Learning><Role><SAPK2A><Scaffolding Protein><Seizure Disorder><Seizures><Site><Sleep disturbances><Spinal Column><Spine><Stress-Activated Protein Kinase 2A><Structure><Surface><Synapses><Synaptic><Synaptic Boutons><Synaptic Terminals><Synaptic Transmission><Synaptic plasticity><Telemetries><Telemetry><Testing><Therapeutic><Training><UBE3A><UBE3A gene><Ubiquitilation><Ubiquitin-Protein Ligase E3A><Ubiquitination><Ubiquitinoylation><Vertebral column><Voltage-Gated K+ Channels><Voltage-Gated Potassium Channel><Wild Type Mouse><X-linked intellectual disability><X-linked mental deficiency-megalotestes syndrome><X-linked mental retardation with fragile X syndrome><X-linked mental retardation-fragile site 1 syndrome><a beta peptide><aberrant sleep><abeta><adaptation behavior><adaptive behavior><age associated><age correlated><age dependent><age linked><age related><age specific><amyloid beta><amyloid-b protein><antagonism><antagonist><autism spectral disorder><autism spectrum disorder><autism-fragile X (AFRAX) syndrome><autistic spectrum disorder><backbone><behavior test><behavioral impairment><behavioral test><beta amyloid fibril><bound protein><cell type><cerebellar Purkinje cell><cognitive enhancement><compare to control><comparison control><developmental><disrupted sleep><disturbed sleep><driving><electrophysiological><epilepsia><epileptogenic><experience><fire><flexibility><flexible><fra(X) syndrome><fra(X)(28) syndrome><fra(X)(q27) syndrome><fra(X)(q27-28) syndrome><fragile X-mental retardation syndrome><fragile Xq syndrome><fragile site mental retardation 1><genome mutation><high risk><hippocampal><hippocampal pyramidal neuron><impaired behavior><impaired sleep><imprint><improved><information processing><intellectual and developmental disability><irregular sleep><knockin mice><learned behavior><learning behavior><limited intellectual functioning><long term memory><longterm memory><loss of function><macro-orchidism-marker X (MOMX) syndrome><macro-orchidism-marker X syndrome><mar(X) syndrome><marker X syndrome><mental retardation-macroorchidism syndrome><microtubule bound tau><microtubule-bound tau><morris water maze><morris watermaze><mouse model><murine model><mutant><neural inflammation><neurodevelopmental disease><neuroinflammation><neuroinflammatory><neuron development><neuronal><neuronal circuit><neuronal circuitry><neuronal development><neuronal excitability><novel><p38><p38 MAP Kinase><p38 MAPK Gene><p38 Mitogen Activated Protein Kinase><p38 Protein Kinase><p38 SAPK><p38-Alpha><p38Alpha><patch clamp><pathway><patient living with Alzheimer's disease><patient suffering from Alzheimer's disease><patient with Alzheimer's><patient with Alzheimer's disease><pharmacologic><post-synaptic nerves><post-synaptic neurons><postsynaptic nerves><postsynaptic neurons><preservation><prevent><preventing><primary degenerative dementia><puppetlike syndrome><senile dementia of the Alzheimer type><sleep disruption><sleep dysregulation><social role><soluble amyloid precursor protein><synapse><tau><tau Proteins><tau factor><telemetric><trafficking><ubiquination><ubiquitin conjugation><voltage gated channel><wildtype mouse><τ Proteins>