Identification of genes conferring susceptibility in a preclinical model of PTSD

James A. Haley Va Medical Center, Tampa FL

Investigators

Abstract

PTSD is recognized as one of the “invisible” wounds of war. Military figures report rates ranging from 13 to 30% lifetime prevalence amongst service members returning from combat zones. Within this group, combat exposure produces a virulent form of PTSD that is refractory to current treatment, and remission of symptoms is reported in only very few patients. There is therefore a pressing need to advance our current understanding of the underlying neurobiological responses to trauma in much greater depth and detail than previously. It remains unknown why only a fraction of patients exposed to traumatic events develop PTSD. Delineating risk and resiliency factors could provide clues to better understand the mechanisms driving resilience and susceptibility to stress exposure and thus lead to the development of tailored preventative interventions. One method of tackling this is to use single cell transcriptomics to identify disease associated neural cell subpopulations and their transcriptomic profiles that drive clinical traits. Conducting such studies in humans carries several inherent challenging problems. Thus, our approach to this problem is to utilize a clinically relevant, well characterized laboratory model, in which many variables can be controlled. We have developed and characterized a unique mouse model of exposure to multiple stressors that results in acute and, most importantly, chronic behavioral and neuroendocrine changes, recapitulating findings in human PTSD patients. Like humans, our model displays a notable heterogeneity in response to stress, with some mice demonstrating little effect of the stress exposure, while others are severely compromised. In this proposal, we will use a single cell transcriptomic approach in our mouse model of stress exposure to identify disease associated neural cell subpopulations and their key regulatory genes that function as a molecular switch driving susceptibility to stress. We will expose a large cohort of mice to our stress paradigm and perform behavioral assessments to discriminate between high (susceptible) vs low (resilient) responding mice. We will employ an unbiased scRNAseq mining approach to interrogate single cell transcriptomic profiles in the amygdala, hippocampus and medial prefrontal cortex that drive behavioral phenotypes in high vs low responding mice. From this molecular library of transcriptomic responses, we will identify the candidate upstream regulators driving the neurobiological changes involved in susceptibility to stress. In future studies we will map our single cell (mouse) transcriptomic data with our collaborator’s human transcriptomic database of PTSD cases, and confirm translationally relevant mouse gene hits by intersection with human PTSD genes identified from autopsy tissue. Candidate genes, representing molecular drivers, will undergo successive interrogation for their functional and therapeutic roles at multiple levels. Validation in primary cell cultures and in vivo, will assess the impact of their silencing or overexpression in promoting stress responsive molecular pathways and behavioral susceptibility. The most promising genes will be selected, for in vivo therapeutic target validation in our model using adeno-associated virus therapy. The overarching goal of this proposal is to capitalize on our translationally relevant mouse model to identify candidate novel therapeutic targets in PTSD. This work will provide a foundation for further validation and IND-enabling studies of well rationalized approaches, designed to address the growing population of PTSD patients suffering from this highly debilitating disorder.