Project description:Pain is an unpleasant experience caused by intense heat or mechanical force. How the spinal cord neural circuits attribute differences in quality of noxious information such as the psychophysically distinct modalities remain unknown. By means of genetic capture, activity manipulation and scRNA sequencing, we identified distinct neural ensembles in the spinal cord encoding mechanical and heat pain. Re-activation or silencing these ensembles potentiated or stopped, respectively, affective but not reflex behaviour without altering pain behaviour to cross stimuli modality. Within ensembles, excitatory neurons encoded quality and a single molecular type of polymodal Gal+ inhibitory neuron type gated affective pain regardless of modality. Following peripheral nerve injury there was a marked circuit-wide molecular perturbation associated with inflammation and the ensembles failed to respect noxious information quality and to resolve allodynia and hypersensitivity in mice. Our results reveal the existence of a spinal representation of cutaneous noxious heat and mechanical stimuli which forms the neural basis of the affective qualities of acute pain perception and that these are under the control of feedforward inhibition by a shared inhibitory neuron type.
Project description:The physical manifestations of memory formation and recall are fundamental questions that remain unresolved. At the cellular level, ensembles of neurons called engrams are activated by learning events and control memory recall. Astrocytes are in close proximity to neurons and engage in a range of activities that support neurotransmission and circuit plasticity. Moreover, astrocytes exhibit experience dependent plasticity; however whether specific ensembles of astrocytes participate in memory recall remains obscure. Here we show that learning events induce c-Fos expression in a subset of hippocampal astrocytes, which subsequently regulates hippocampal circuit function. Intersectional, c-Fos based labeling of these astrocyte ensembles after learning events reveals that they are closely affiliated with engram neurons, while re-activation of these astrocyte ensembles stimulates memory recall. At the molecular level, these astrocyte ensembles exhibit elevated expression of NFIA and its selective deletion from this population suppresses memory recall. Together, our studies identify learning-associated astrocyte ensembles as a new form of plasticity that is sufficient to provoke memory recall, while implicating astrocytes as a reservoir for the storage of memories.
Project description:Sleep and affective behaviors are highly interrelated phenotypes, commonly altered in a variety of neuropsychiatric diseases, including major depressive disorder (MDD). To understand the transcriptomic organization underlying sleep and affective function, we studied a population of (C57BL/6J x 129S1/SvImJ) F2 mice by measuring 283 affective and sleep phenotypes and profiling gene expression across four brain regions, including the frontal cortex, hippocampus, thalamus, and hypothalamus. We identified converging molecular bases for sleep and affective phenotypes at both the single-gene and gene-network levels. Utilizing publicly available transcriptomic datasets collected from sleep-deprived mice and major depressive disorder (MDD) patients, we identified three cortical gene networks altered by sleep/wake changes and depression. The network-level actions of sleep loss and depression were opposite to each other, providing a mechanistic basis for the sleep disruptions commonly observed in depression as well as the reported acute antidepressant effects of sleep deprivation. We highlight one particular network composed of circadian rhythm regulators and neuronal activity-dependent immediate-early genes. The key upstream driver of this network, Arc, may act as a nexus linking sleep and depression. Our data provide mechanistic insights into the role of sleep in affective function and MDD.
Project description:Empathy is crucial for our social lives, and its disruption is a prominent characteristic of various psychiatric conditions. However, the specific genes and neurobiological mechanisms underlying empathy deficits remain elusive. By combining forward genetic mapping with transcriptome analysis, we discovered that the Arnt2 gene encoding a basic-helix-loop-helix (bHLH)-PAS transcription factor is a key driver of significant alteration in observational fear, a basic form of affective empathy. Selective deletion of Arnt2 in somatostatin (SST)-expressing inhibitory neurons resulted in reduced excitability of pyramidal cells, an increase in spontaneous firing, and alteration in in vivo Ca2+ dynamics in SST neurons in the anterior cingulate cortex (ACC), leading to deficits in observational fear and affective state discrimination. Together, our findings provide the first direct evidence that ARNT2 regulates emotion recognition and affect sharing through its functional actions in the cortical inhibitory circuit and highlight the neural substrates underlying social affective dysfunctions in psychiatric disorders.
Project description:Maladaptive reward seeking is a hallmark of cocaine use disorder. To develop therapeutic targets, it is critical to understand the neurobiological changes specific to cocaine-seeking without altering the seeking of natural rewards, e.g., sucrose. The prefrontal cortex (PFC) and the nucleus accumbens core (NAcore) are known regions associated with cocaine- and sucrose-seeking ensembles, i.e., a sparse population of co-activated neurons. Within ensembles, transcriptomic alterations in the PFC and NAcore underlie the learning and persistence of cocaine- and sucrose-seeking behavior. However, transcriptomes exclusively driving cocaine seeking independent from sucrose seeking have not yet been defined using a within-subject approach. Using Ai14:cFos-TRAP2 transgenic mice in a dual cocaine and sucrose self-administration model, we fluorescently sorted (FACS) and characterized (RNAseq) the transcriptomes defining cocaine- and sucrose-seeking ensembles. We found reward- and region-specific transcriptomic changes that will help develop clinically relevant genetic approaches to decrease cocaine-seeking behavior without altering non-drug reward-based positive reinforcement.
Project description:Nuclear receptors function as ligand-regulated transcription factors whose ability to regulate diverse physiological processes is closely linked with conformational changes induced upon ligand binding. Understanding how conformational populations of nuclear receptors are shifted by various ligands could illuminate strategies for the design of synthetic modulators to regulate specific transcriptional programs. Here, we investigate ligand-induced conformational changes using a reconstructed, ancestral nuclear receptor. By making substitutions at a key position, we engineer receptor variants with altered ligand specificities. We use atomistic molecular dynamics (MD) simulations with enhanced sampling to generate ensembles of wildtype and engineered receptors in combination with multiple ligands, followed by conformational analysis and prediction of ligand activity. We combine cellular and biophysical experiments to allow correlation of MD-based predictions with functional ligand profiles, as well as elucidation of mechanisms underlying altered transcription in receptor variants. We determine that conformational ensembles accurately predict ligand responses based on observed population shifts, even within engineered receptors that were constitutively active or transcriptionally unresponsive in experiments. These studies provide a platform which will allow structural characterization of physiologically-relevant conformational ensembles, as well as provide the ability to design and predict transcriptional responses in novel ligands.