Related Experiment Video
Updated: Aug 20, 2026
Evaluation of Synapse Density in Hippocampal Rodent Brain Slices
Published on: October 6, 2017
Neuronal Ddit4 Overexpression in the Medial Prefrontal Cortex Reduces Synaptic Density and Impairs Cognitive Function
Alexander M Kuhn1, Kelly E Bosis2, Madeline M Mairose1
1Department of Pharmacology, Physiology, & Neurobiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267.
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 deficits 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.
Insights
Increased neuronal DNA Damage-Inducible Transcript 4 (Ddit4) expression in the prefrontal cortex (PFC) impairs temporal order memory and reduces dendritic spine density. This suggests Ddit4 overexpression mimics chronic stress effects through a cell-autonomous mechanism.
Area of Science:
- Neuroscience
- Molecular Biology
- Psychiatry
Background:
- Chronic stress induces neurobiological changes similar to major depressive disorder (MDD).
- DNA Damage-Inducible Transcript 4 (Ddit4) is elevated in the prefrontal cortex (PFC) in stress models and MDD patients.
- DDIT4 inhibits the mammalian target of rapamycin (mTOR) pathway, potentially causing behavioral deficits via reduced neuroplasticity.
Purpose of the Study:
- To investigate if increased neuronal Ddit4 expression in the PFC is sufficient to cause structural neuronal remodeling.
- To determine if Ddit4 overexpression provokes microglia activation and leads to behavioral and cognitive deficits.
- To elucidate the cell-autonomous effects of Ddit4 on PFC function and associated behaviors.
Main Methods:
- Adeno-associated virus-mediated Ddit4 overexpression (Ddit4-OV) or control vector infusion into the mouse PFC.
- Assessment of molecular, cellular (e.g., dendritic spine density), and behavioral endpoints (e.g., temporal order memory).
- Bulk RNA sequencing of PFC tissue to analyze transcriptomic changes.
Main Results:
- Ddit4-OV mice exhibited deficits in temporal order memory but not passive stress coping.
- Immunohistology revealed decreased dendritic spine density in Ddit4-OV mice.
- RNA sequencing showed altered transcripts related to dendrite/synapse function and mitochondrial function, suggesting mTOR dysregulation.
Conclusions:
- Neuronal Ddit4 overexpression is sufficient to reduce PFC spine density and impair temporal order memory.
- Ddit4 overexpression recapitulates molecular, cellular, and behavioral adaptations seen after chronic stress via a cell-autonomous mechanism.
- These findings highlight the role of neuronal Ddit4 in disrupting PFC function and cognitive performance, relevant to stress and depression.
