Gene Expression Analysis Reveals Dysregulation in Traumatic Brain Injury Leading to Tauopathy

Graduation Year

2024

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Pharmacy

Major Professor

Subhra Mohapatra, Ph.D.

Committee Member

Umesh Jinwal, Ph.D.

Committee Member

Alison Willing, Ph.D.

Abstract

Traumatic Brain Injury (TBI) causes a cascade of detrimental events within neurons, contributing to a host of neurological diseases relating to dementia. In this study we have performed a meta-analysis comparing differentially expressed genes (DEG) in specific cell types such as neurons and microglia revealing inflammation as a common driver of neurological deficiencies post TBI. Inflammation and hypoxia are well characterized features of TBI; however, the molecular mechanisms causing tau hyperphosphorylation by tauopathy associated genes (TAG) post-TBI are currently poorly understood. Furthermore, there are limited in-vitro neuroinflammatory models that mimic primary and secondary TBI. We hypothesize that inducing hypoxia and inflammation in a neuronal cell line in vitro will mimic TBI, in-vivo, which may reveal up-regulated tauopathy associated genes. Using publicly available data sets from the NCBI Gene Expression Omnibus (GEO) database, we compared DEG expression in mouse brain tissue from TBI vs sham injury at 24hr to 14 months post injury. Ingenuity Pathway Analysis (IPA) software was used to investigate the regulatory networks containing DEG’s, identify central “hub genes”, and predict downstream effects of the observed expression changes. Neuronal cell lines were treated with varying doses of LPS, Cobalt Chloride, or their combination to replicate the inflammation and hypoxia of secondary TBI. Quantitative RT- PCR was used to confirm the appearance of TAG. The findings of this project include a comparison of short vs long term pathology correlating an early inflammatory response to later dysregulation of tau metabolism. We furthermore defined a set of common DEG in mouse models of TBI which are known to correlate with Alzheimer’s disease and TAG. Dual insulted neuronal cells mimicked gene expression changes of secondary TBI as observed by q-RT-PCR. Comparing the multiple independent studies, at different time periods, has provided novel insight into which DEG are upregulated at early vs late time-points to further narrow down the mechanism of dysregulated tau metabolism post-TBI. The dual insult in-vitro model confirmed phenotypic changes in neuronal cell line indicating secondary inflammatory effects mimicking TBI. This will be further investigated to determine the contribution of these genes to tau phosphorylation and aggregation.

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