Traumatic brain injury (TBI) has a complex neuropathology involving progressive alterations in brain centers that process cognitive and emotional behaviors and consist of heterogeneous cell populations. The complex spatiotemporal cell and molecular circuits underlying progressive TBI pathologies that can evolve into other disorders such as chronic traumatic encephalopathy and posttraumatic stress disorder remain to be understood. A comprehensive understanding of the molecular mechanisms underlying the complexity of TBI has been hindered by the lack of effective approaches to examine molecular events in individual brain cells that drive the overall pathology. We recently conducted a single cell resolution study of the hippocampus at the acute phase (24hr) of TBI using single cell RNA sequencing (scRNAseq) and revealed cell-type specific pathways and regulators of TBI. In particular, we found that depression of cell metabolism to be a key pathogenic component in the hippocampus at the acute phase of TBI. This finding suggests that tracking metabolic state of cells can be used to address key knowledge gaps on the spatial and time dependent progression of key pathologic drivers of TBI. Here we propose to test the hypothesis that cell metabolic regulators determine dynamic and spatial pathogenic pathways of TBI by harnessing the power of modern high-throughput technologies. We propose a highly integrative team approach to profit from recent advances in single cell RNA sequencing (scRNAseq) and multiplexed error robust fluorescent in situ hybridization (MERFISH) along with advanced gene-gene and cell-cell network modeling to inform on targets for intervention at specific time points or brain sites, a fundamental unsolved question in the TBI field.
In Aim 1, we propose to utilize a unique combination of scRNAseq, MERFISH, and network modeling approaches to assess and validate the spatial and temporal vulnerability of each cell type to TBI in multiple brain regions at multiple time points in a data-driven, unbiased manner, which can inform us about hidden regulators of TBI pathogenesis. We will focus on the spatial and temporal changes in cellular metabolic pathways during TBI progression. Our preliminary results support that mt-Rnr2, encoding a mitochondrial peptide humanin and involved in cell metabolism, is a major site- and time-dependent driver of TBI.
In Aim 2, we will functionally assess whether modulating mt-Rnr2 (humanin) has therapeutic potential to mitigate TBI pathology and prevent progression. We will also explore the cell-type specific mechanisms, especially the role of metabolism, underlying the actions of humanin. The overall goal of the proposal is to elaborate on an innovative strategy that can offer a comprehensive mechanistic understanding of the spatiotemporal cell substrates of TBI pathology and uncover novel targets and mechanisms to redirect the courses of TBI to overcome subsequent neurological disorders.
Using a multidisciplinary team approach, we are poised to map the cell-type specific genes, pathways, networks, and circuits vulnerable to the TBI pathology across brain regions and time points. We will use a combination of single cell RNA sequencing technology (scRNAseq), multiplexed error robust fluorescent in situ hybridization (MERFISH), advanced network modeling, and experimental validation and functional studies to unravel novel and fundamental gene and cell connectivity perturbations that can be used as biomarkers and targets of TBI in a data-driven, unbiased manner.
