Biomedical subjects

Jesse E Hanson

Publications and source records attributed to Jesse E Hanson.

8 recordsLinked to original sources

PubMed2026

A massively parallel CRISPR-based screening platform for modifiers of neuronal depolarization.

Understanding the complex interplay between gene expression and neuronal activity is crucial for unraveling the molecular mechanisms underlying cognitive function and neurological disorders. Here, we developed pooled screens using CRISPR interference (CRISPRi) and the fluorescent calcium integrator CaMPARI2 to evaluate genetic modifiers of neuronal depolarization. Using this screening method, we evaluated 1343 genes for their effect on depolarization in a human iPSC-derived neuron model, revealing potential links to neurodegenerative and neurodevelopmental disorders. These genes include known regulators of neuronal excitability, such as TARPs and ion channels, as well as genes associated with autism spectrum disorder and Alzheimer's disease not previously described to affect neuronal depolarization. This CRISPRi-based screening platform offers a versatile tool to uncover molecular mechanisms controlling neuronal function in health and disease.

Humans↗

PubMed2025

A Massively Parallel CRISPR-Based Screening Platform for Modifiers of Neuronal Activity.

Understanding the complex interplay between gene expression and neuronal activity is crucial for unraveling the molecular mechanisms underlying cognitive function and neurological disorders. Here, we developed pooled screens for neuronal activity, using CRISPR interference (CRISPRi) and the fluorescent calcium integrator CaMPARI2. Using this screening method, we evaluated 1343 genes for their effect on excitability in human iPSC-derived neurons, revealing potential links to neurodegenerative and neurodevelopmental disorders. These genes include known regulators of neuronal excitability, such as TARPs and ion channels, as well as genes associated with autism spectrum disorder and Alzheimer's disease not previously described to affect neuronal excitability. This CRISPRi-based screening platform offers a versatile tool to uncover molecular mechanisms controlling neuronal activity in health and disease.

Journal Article↗

PubMed2006

The functional nature of synaptic circuitry is altered in area CA3 of the hippocampus in a mouse model of Down's syndrome.

Down's syndrome (DS) is the most common cause of mental retardation, and memory impairments are more severe in DS than in most if not all other causes of mental retardation. The Ts65Dn mouse, a genetic model of DS, exhibits phenotypes of DS, including memory impairments indicative of hippocampal dysfunction. We examined functional synaptic connectivity in area CA3 of the hippocampus of Ts65Dn mice using organotypic slice cultures as a model. We found reductions in multiple measures of synaptic function in both excitatory and inhibitory inputs to pyramidal neurons in CA3 of the Ts65Dn hippocampus. However, associational synaptic connections between pyramidal neurons were more abundant and more likely to be active rather than silent in the Ts65Dn hippocampus. Synaptic potentiation was normal in these associational connections. Decreased overall functional synaptic input onto pyramidal neurons expressed along with the specific hyperconnectivity of associational connections between pyramidal neurons will result in predictable alterations of CA3 network function, which may contribute to the memory impairments seen in DS.

Animals↗

PubMed2005

Blocking polysynaptic inhibition via opioid receptor activation isolates excitatory synaptic currents without triggering epileptiform activity in organotypic hippocampal slices.

The abundance of synaptic connectivity in the cultured hippocampal slice preparation allows measurements of the unitary excitatory connection between pairs of pyramidal neurons using simultaneous presynaptic and postsynaptic intracellular recordings. However, the useful yield of these recordings can be greatly reduced by the presence of polysynaptic inhibition that occludes the measurement of the monosynaptic excitatory postsynaptic current (EPSC). We have found that the traditional method of eliminating contaminating synaptic inhibition with GABA receptor antagonists is of limited usefulness because the recurrent excitatory connections in organotypic slices cause epileptiform bursting in the absence of inhibitory function. This bursting obscures EPSCs to an even greater extent than the normally occurring polysynaptic inhibitory transmission. Here, we report a new method for isolating monosynaptic EPSCs using the mu-opioid agonist peptide DAMGO to reduce polysynaptic inhibition during these recordings. Activation of mu-opioid receptors is known to hyperpolarize inhibitory neurons. We found that DAMGO application reduces the amplitude and frequency of polysynaptic inhibition, allowing isolation of the excitatory connection between the two neurons being recorded. Furthermore, because inhibitory function is not completely eliminated by DAMGO application, epileptiform bursting very rarely develops. Therefore, the use of DAMGO to prevent polysynaptic inhibition without causing epileptiform bursting provides a useful tool to substantially increase the yield of experiments measuring the unitary excitatory connection between pyramidal neurons in the cultured hippocampal slice preparation.

Analgesics, Opioid↗

PubMed2005

Dynamin-dependent NMDAR endocytosis during LTD and its dependence on synaptic state.

BACKGROUND: The N-methyl-D-aspartate (NMDA)-type glutamate receptor expressed at excitatory glutamatergic synapses is required for learning and memory and is critical for normal brain function. At a cellular level, this receptor plays a pivotal role in triggering and controlling synaptic plasticity. While it has been long recognized that this receptor plays a regulatory role, it was considered by many to be itself immune to synaptic activity-induced plasticity. More recently, we and others have shown that NMDA receptor-mediated synaptic responses can be subject to activity-dependent depression. RESULTS: Here we show that depression of synaptic transmission mediated by NMDA receptors displays a state-dependence in its plasticity; NMDA receptors are resistant to activity-induced changes at silent and recently-silent synapses. Once synapses transition to the active state however, NMDA receptors become fully 'plastic'. This state-dependence is identical to that shown by the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor. Furthermore, the down-regulation of NMDAR-mediated responses during synaptic depression is prevented by disruption of dynamin-dependent endocytosis. CONCLUSION: NMDA receptor-mediated synaptic responses are plastic in a state-dependent manner. Depending on the plasticity state in which a synapse currently resides, NMDA receptors will either be available or unavailable for down-regulation. The mechanism underlying the down-regulation of NMDA receptor-mediated synaptic responses is endocytosis of the NMDA receptor. Other potential mechanisms, such as receptor diffusion along the plane of the membrane, or changes in the activity of the channel are not supported. The mechanisms of AMPA receptor and NMDA receptor endocytosis appear to be tightly coupled, as both are either available or unavailable for endocytosis in the same synaptic states. Endocytosis of NMDA receptors would serve as a potent mechanism for metaplasticity. Such state-dependent regulation of NMDAR endocytosis will provide fundamental control over downstream NMDA receptor-dependent plasticity of neuronal circuitry.

Animals↗

PubMed2004

Sodium channels and dendritic spike initiation at excitatory synapses in globus pallidus neurons.

Glutamatergic inputs from the subthalamic nucleus are suspected to provide a prominent source of excitation to globus pallidus (GP) neurons, despite their scarce number and mainly distal dendritic location. In this study we address the issue of whether dendritic sodium channels may facilitate the effect of excitatory inputs in GP. First, we examined the subcellular distribution of sodium channels using electron microscopic observations of immunoperoxidase and immunogold labeling. Voltage-gated sodium channels were found throughout GP dendrites and furthermore exhibited a specific clustering at sites of excitatory synaptic inputs. To examine the possibility that these channels could mediate dendritic spike generation, synaptic stimulation at visualized dendritic sites was performed during whole-cell recordings in vitro. These recordings revealed dendritic spike initiation in response to small excitatory inputs even for very distal stimulation sites. In contrast, subthreshold responses were mostly or fully attenuated at the soma for stimulation sites on distal dendrites. Computer simulations support the hypothesis that postsynaptic clustering of sodium channels allows dendritic triggering of spikes in response to inputs that would be too small to trigger a spike given uniformly distributed dendritic sodium channels. These findings indicate that postsynaptic sodium channel clustering is an effective mechanism to mediate a novel form of synaptic amplification and dendritic spike initiation. The ability of small amounts of excitation to trigger spikes in GP dendrites supports the prominent role of subthalamic input in the control of GP activity.

Action Potentials↗

PubMed2002

Short-term plasticity shapes the response to simulated normal and parkinsonian input patterns in the globus pallidus.

Basal ganglia structures show strong activity modulation during movement and synchronous bursting in Parkinson's disease. Recent work has shown that short-term synaptic plasticity (STP) can play an important role in the effect of temporal activity patterns on postsynaptic targets. To determine the role of STP in the subthalamic nucleus (STN) to globus pallidus (GP) connection, which has been suggested to underlie rhythmical bursting in Parkinson's disease, we first measured STP using trains of electrical input stimulation in vitro. We found that STN inputs to GP typically show both facilitation and depression with input frequencies of 10-100 Hz and that facilitation is dominant for the first few inputs in a train but that depression takes over subsequently. We quantified the strength and time course of facilitation and depression using a computational model of STP. Using the STP model, we constructed synaptic conductance patterns of normal and Parkinsonian STN activity and applied these conductances to GP neurons in vitro using the technique of dynamic clamping. We show that STP controls the slope and shape of the function describing the steady-state level of GP neuron firing in response to different levels of STN input. In addition, we show that STP modulates responses of GP neurons to bursts and pauses in the input pattern. These findings indicate that STP plays an important role in modulating both spike rates and temporal patterns of GP activity in the normal state, as well as in Parkinson's disease.

Afferent Pathways↗

PubMed2002

Subcellular distribution of high-voltage-activated calcium channel subtypes in rat globus pallidus neurons.

Globus pallidus (GP) neurons receive dense inhibitory synaptic inputs interspersed with sparse excitatory inputs distributed across the entire extent of their somata and dendrites. Yet, despite this predominance of inhibitory influence, GP neurons fire at a high tonic rate, suggesting that intrinsic properties play an important role in determining the physiological characteristics of these neurons. High-voltage-activated (HVA) calcium channels represent an important class of conductances that plays roles in controlling neurotransmitter release, postsynaptic excitability, and intracellular calcium signaling. To better understand the intrinsic properties of GP neurons, we examined the subcellular localization of HVA calcium channels by using immunocytochemistry at the electron microscopic level. Peroxidase labeling with antibodies against P/Q-, N-, and R-type HVA calcium channels demonstrated the presence of these channels in both proximal and distal dendrites of GP neurons. P/Q-, N-, and R-type channels were also found in presynaptic terminals, whereas L-type channels were found exclusively postsynaptically in neuronal elements. Immunogold labeling demonstrated that, although the density of intracellular L-type calcium channel labeling remains constant throughout the proximal-distal extent of the dendritic tree of GP neurons, the density of plasma membrane-bound channels is greater in distal dendrites. The finding of HVA calcium channels distributed throughout the whole dendritic tree of GP neurons indicates that these channels may interact with synaptic inputs to allow rich processing possibilities for GP neuron dendrites. Furthermore, the finding of a greater density of plasma membrane-bound L-type channels in distal dendrites expands the view that L-type channels are important only in somatic and proximal locations.

Animals↗