It is demonstrated that Ddit4 overexpression specifically in neurons is sufficient to reduce spine density in the PFC, impair temporal order memory, and induce transcriptional changes associated with stress and depression.
Abstract
Chronic stress exposure causes neurobiological and behavioral changes that resemble those reported in psychiatric conditions such as major depressive disorder (MDD). Preclinical stress models and studies using postmortem tissue from MDD patients have shown that DNA Damage-Inducible Transcript 4 (Ddit4) is increased in the prefrontal cortex (PFC). This is important because DDIT4 negatively regulates the mammalian target of rapamycin (mTOR) pathway, which may lead to behavioral deficits through diminished neuroplasticity and PFC function. Our prior studies indicate that coordinated neuron-microglia interactions contribute to synaptic remodeling in the PFC. The present studies aimed to test the hypothesis that increased neuronal Ddit4 expression is sufficient to drive structural remodeling of PFC neurons, in part by provoking microglia activation, and this leads to behavioral and cognitive deficits. To this end, we bilaterally infused AAV5-hSyn1-Ddit4-tdTomato or a control vector into the PFC of male Thy1-GFP and C57BL/6 mice and examined molecular, cellular, and behavioral endpoints. Mice with Ddit4 overexpression (Ddit4-OV) showed no change in passive stress coping yet exhibited a deficit in temporal order memory. Immunohistology analyses showed a decrease in dendritic spine density of Ddit4-OV mice. However, we found no changes in microglia count, microglia size, or nearest neighbor distance. Bulk RNA sequencing of Ddit4-OV PFC revealed increases in transcripts involved with dendrite and synapse function and decreases in transcripts involved with mitochondrial function, implicating mTOR dysregulation. Altogether, these results indicate that Ddit4 overexpression recapitulates some of the broad molecular, cellular, and behavioral adaptations observed following chronic stress exposure through a cell-autonomous mechanism.Significance Statement This work provides more context for the neurobiological effects of neuronal DNA Damage-Inducible Transcript 4 (Ddit4). Ddit4, an inhibitor of the mammalian target of rapamycin (mTOR) pathway, exhibits increased expression in the prefrontal cortex (PFC) of both rats exposed to pre-clinical chronic stress models and humans diagnosed with major depressive disorder (MDD). Our findings demonstrate that Ddit4 overexpression specifically in neurons is sufficient to reduce spine density in the PFC, impair temporal order memory, and induce transcriptional changes associated with stress and depression. These results indicate that neuronal Ddit4 can disrupt PFC function and cognitive performance in a cell-autonomous manner.
Schizophrenia, major depressive disorder (MDD), and Alzheimer's disease (AD) involve dysfunction of distributed cortical-subcortical networks that support complex cognitive processes and emotion regulation. Convergent evidence identifies the dorsolateral prefrontal cortex (dlPFC) as a critical site of molecular, cellular, and circuitry alterations in these disorders. The primate dlPFC contains recurrent, excitatory microcircuits in layer III that sustain working memory and top-down control through specialized forms of neurotransmission and intracellular signaling. Specifically, NMDA receptor and cholinergic modulation, as well as tightly regulated calcium-cAMP signaling within dendritic spines, support task-specific firing of layer III pyramidal neurons, but may also increase vulnerability to genetic risk, stress, inflammation and aging. This review integrates findings from human postmortem studies, neuroimaging, and genetics to examine how dlPFC circuitry is altered in these disease states. In schizophrenia, layer III pyramidal neurons exhibit altered synaptic and cytoskeletal signaling, lower dendritic spine density, and compensatory shifts in inhibitory inputs that likely weaken recurrent excitation and network synchrony. In MDD, dysfunction of dlPFC pathways regulating subgenual cingulate cortex contributes to impaired top-down control of emotion and motivation. In AD and frontotemporal lobar degeneration, tau pathology and neurodegeneration target association cortices, including layer III dlPFC circuits, contributing to progressive cognitive decline and impaired executive function. The review also highlights how studies in rhesus macaques and genetically engineered marmosets have provided important insight into the organization, physiology, and disease vulnerability of primate dlPFC circuits. Together, these findings inform the development of emerging therapeutic strategies aimed at strengthening prefrontal network function.
D. Datta, A. Arnsten, Stacey J. Sukoff Rizzo et al.· Biological Psychiatry· 0 citations
Major depressive disorder (MDD) is associated with reduced hippocampal volume, altered connectivity and negative memory bias, suggesting disrupted hippocampal plasticity. Dysregulated adult hippocampal neurogenesis is a potential contributor, but its relevance in humans and role in MDD remain unclear. Here we investigated the molecular basis of hippocampal dysfunction in nonmedicated individuals with MDD by integrating analyses of neurogenic trajectories, cell-type- and subfield-specific gene expression, chromatin accessibility and protein expression. We identify a neurogenic lineage in the adult human hippocampal subgranular zone and provide evidence for a stalled neurogenic process in MDD, associated with transcriptional regulation, stress-related reprogramming and interferon signaling across developmental stages. Excitatory and inhibitory neurons show dysregulation of transcription factor networks affecting cell states. Cellular stress, excitatory-inhibitory imbalance, impaired synaptic plasticity, reduced metabolic capacity and immune activation, underlie impaired neurogenesis and reduced hippocampus circuit plasticity. Findings indicate genetic and epigenetic regulation of gene expression in MDD, and overlapping pathogenetic mechanisms with autoimmune, neurodevelopmental and neurodegenerative diseases. This work provides a new understanding of the pathogenesis of hippocampus-dependent cognitive symptoms in MDD and suggests potential therapeutic targets.
Madeleine S Peng, Jia-Jia Jiang, Luciana Polizzi et al.· Nature Medicine· 1 citation
Results suggest that Adgrd1 plays a key role in maintaining hippocampal resilience and regulating motivational behaviors through integrated molecular and circuit-level mechanisms.
Inés Martínez-Soria, Pol Picón-Pagès, A. P. Pérez González et al.· bioRxiv· 0 citations
The pathophysiology of depression involves multiple biological processes, including circuit dysfunction and impaired neuroplasticity, yet an integrative view linking these processes remains elusive. Here, we identify a convergent circuit for antidepressant response and plasticity modulation. We demonstrate that chemogenetic activation of the infralimbic cortex (IL) exerts rapid antidepressant-like effects across multiple behavioral domains in a mouse model of stress-induced depression. IL stimulation exerts top-down control over the hippocampus, enhancing structural plasticity, restoring long-term potentiation deficits and improving state-dependent network dynamics in the ventral hippocampus (vHIPP). We identify the thalamic nucleus reuniens (RE) as a necessary mediator of these effects. Notably, direct inhibition of RE, its inputs from IL or projections to vHIPP, blocks both IL stimulation-induced antidepressant response and the therapeutic and neuroplastic effects of ketamine. Our findings demonstrate that the functional IL → RE→vHIPP circuit plays a central role in the antidepressant response, linking circuit activity, hippocampal plasticity, and depressive-like behaviors. Neural mechanisms underlying depression are not fully understood. This study identifies a prefrontal–thalamic–hippocampal circuit that links antidepressant-like behavior with restored neural plasticity and is required for ketamine’s behavioral and neuroplastic effects in mice.
M. Veleanu, Louise Schuberth, Antje Kilias et al.· Nature Communications· 0 citations
Depression is one of the most prevalent mental disorders worldwide. The limited clinical efficacy of current antidepressants highlights identifying new therapeutic targets. Emerging evidence suggests that dysfunction of oligodendrocyte lineage cells contributes to the pathophysiology of depression. Teneurin-4 (Tenm4), a transmembrane protein that promotes oligodendrocyte differentiation and myelination, has been implicated in psychiatric disorders in genome-wide association studies; however, its causal role remains unclear. To determine whether Tenm4 contributes to depressive-like behavioral phenotypes, we examined Tenm4 protein expression in mice exposed to repeated forced swimming stress and generated hippocampal Tenm4 knockdown (Tenm4KD) mice. Chronic stress reduced Tenm4 expression levels in the hippocampus. Mice with hippocampus-specific Tenm4KD exhibited depressive-like behaviors, accompanied by reduced hippocampal myelin basic protein. Importantly, administration of clemastine, a myelin formation promoter, inhibited the reduction of myelin and attenuated depression-like behavioral phenotypes. Immunohistochemical analysis showed that Tenm4KD significantly decreased the number of mature oligodendrocyte cells and increased in the number of oligodendrocyte precursor cells, without changes in the total number of oligodendrocyte lineage cells. This study provides the first evidence that hippocampal Tenm4 deficiency induces depression-like behavior phenotypes through impaired oligodendrocyte differentiation and promoting demyelination. Our results identify Tenm4 as a molecular regulator of stress-induced behavioral phenotypes and suggest that it might represent a potential therapeutic target for mood disorders associated with demyelination.
Yuichiro Sugimori, Y. Yano, Takashi Asano et al.· Neuropharmacology· 0 citations
Introduction Early synaptic failure is widely considered a primary driver of cognitive decline in Alzheimer's disease (AD), and previous studies have suggested that dopaminergic signaling may contribute to hippocampal synaptic dysfunction. Among dopaminergic receptors, dopamine D3 receptors (D3Rs) have emerged as important modulators of synaptic plasticity and cognitive processes, but their role in AD-related synaptic impairment remains unclear. The aim of this study was to determine whether pharmacological blockade of D3Rs could restore memory deficits and hippocampal synaptic dysfunction in preclinical models of AD. Methods Behavioral studies, including novel object recognition (NOR), novel object location (NOL), and open-field tests, were performed to evaluate recognition memory, spatial memory, locomotor activity, and anxiety-related behavior in two mechanistically distinct mouse models of AD: triple-transgenic 3xTg-AD mice and α7 nicotinic acetylcholine receptor knockout (α7KO) mice. Electrophysiological recordings in hippocampal slices were used to assess AMPA/NMDA ratio, basal synaptic transmission, and long-term potentiation (LTP). qPCR and western blot analyses were performed to evaluate hippocampal D3R mRNA and protein expression, respectively. Pharmacological treatments included the selective D3R antagonist NGB-2904 and cariprazine, a clinically approved antipsychotic with high affinity for D3Rs. Results Recognition and spatial memory deficits were rescued by NGB-2904 and cariprazine in both AD models, without affecting locomotor activity or anxiety-related behavior. No sex-dependent differences were observed in the behavioral response to treatment. Electrophysiological recordings revealed a reduced AMPA/NMDA ratio and impaired LTP in both models, while basal synaptic transmission was selectively reduced in 3xTg-AD mice. D3R-targeting compounds restored synaptic transmission and plasticity. Inhibition of PKA prevented the rescue of LTP induced by D3R blockade, suggesting the involvement of the cAMP/PKA signaling pathway. Both models displayed reduced hippocampal D3R mRNA expression and protein levels, suggesting that the residual population of D3Rs might represent a viable target. Conclusion Together, these findings demonstrate that D3R-targeting compounds rescue synaptic plasticity and memory deficits in two mechanistically distinct AD models. These results support a role for dopaminergic signaling in early synaptic dysfunction and highlights D3R modulation as a relevant pathway for further investigation in AD-related cognitive impairment.
Maria Rosaria Tropea, Giuseppe Aceto, R. Trovato et al.· Frontiers in Aging Neuroscie...· 0 citations
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