Analysis of Gene Expression in Traumatic Brain Injury

Undergraduate #42
Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology

Prenicia Gant - Grambling State University
Co-Author(s): Rochelle Joseph, Daniel Kincade, Jharrayne McKnight, and Owen L. Reedy, Grambling State University

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Traumatic brain injury (TBI) accounts for nearly 30% of all injury deaths in the United States and there are currently no true quantitative methods to determine the severity of each case. However, several types of genes have been shown to be either over or under expressed when a TBI has taken place. These particular genes code for several proteins including heat shock proteins, chaperonins, neurotrophic growth factors, transcriptional growth promoters and proteinases. Several of these genes also have orthologs in Drosophila melanogaster, making the fruit fly a suitable model organism for investigations into quantitatively analyzing TBI severity. We hypothesized that specific genes involved in stress, neuronal growth, and repair (Hsp70Aa, Cct γ, Appl) would be upregulated as an adaptive response to TBI. We predicted that transcription in general may be downregulated (E2F2), whereas proteases involved in programmed cell death (Cp1) may be upregulated in response to TBI. To test our hypothesis, we induced TBI in Drosophila melanogaster, allowed the flies to rest for four hours, extracted the mRNA, and amplified the genes of interest using reverse transcription polymerase chain reaction (RT-PCR). Gene expression was normalized against the expression of actin 42A and TBI-induced flies were compared to untreated control flies. Our preliminary experiment using a high-impact TBI model resulted in 25% mortality. We observed downregulation of the majority of genes analyzed suggesting that the impact may have been too severe. We followed this experiment with a lowerimpact TBI model that resulted in 0% mortality and observed upregulation of Hsp70Aa and downregulation of Appl in TBIinduced flies. We detected no significant differences in the expression of the other genes of interest. These results suggest
that our TBI model induces damage and stress to which the flies respond by expressing Hsp70Aa. Appl is known to negatively regulate cell death thus its downregulation may indicate an initiation of early cell death. Future research involves identifying additional genes with altered expression in response to TBI.

Funder Acknowledgement(s): This research was supported by NIH/NIGMS MARC U-STAR, Louisiana Board of Regents Enhancement Fund, and the American Society for Cell Biology.

Faculty Advisor: Paul Kim,