Date on Senior Honors Thesis

5-2024

Document Type

Senior Honors Thesis

Degree Name

B.S.

Department

Anatomical Sciences and Neurobiology

Author's Keywords

microglia, spinal cord injury, neuroscience, morphological changes

Abstract

Microglia, immune cells of the central nervous system, constantly survey their environment for damage. Once damage is detected, they are activated into become reactive, resulting in morphological changes, such as larger cell bodies, and functional changes, such as releasing inflammatory mediators. The switch from surveying to reactive occurs because the microglia received signals that sense danger in the environment. The release of Ca2+ from intracellular stores is involved in store-operated calcium entry (SOCE), a signaling pathway. Recent studies have shown that calcium release from the intracellular stores is a factor of microglial activation. SOCE is specific to monitoring low calcium levels and regulating the proper channels to ensure a flow of calcium back into the cell. STIM proteins are ER membrane proteins that monitor calcium concentration in the endoplasmic reticulum. While STIM proteins are important to SOCE and their role in microglial cultures has been explored, their specific role in microglial response to SCI is still poorly understood. I am studying whether STIM1 and STIM2 play any role in microglial response to cervical SCI, specifically monitoring morphological changes. I hypothesize that STIM1 knockout and STIM2 knockout will result in less microglial reactivity to injury because of disturbance to SOCE. Through using an inducible Cre model with activation with tamoxifen, microglial STIM1 and STIM2 can selectively be knocked out. Microglia in extracted spinal cords for STIM1 knockout, STIM2 knockout and STIM wildtype mice were examined through confocal microscopy. Results found that the knockout of STIM1 and STIM2 resulted in the significantly different microglial behaviors as the STIM WT mice, suggesting that STIM1 and STIM2 play a role in inducing morphological changes in microglia as a result to injury.

Lay Summary

Microglia are immune cells of the central nervous system, and they are constantly on the look-out for any damage within their environment. If damage is detected, through environmental cues, they become activated, which means they shift from a surveying state for danger to a reactive state to respond to injury. This change also results in changes to their physical shape, such as their cell body increasing in size. One factor that may cause microglia activation is reduction of calcium concentration in the endoplasmic reticulum within cells. When this reduction happens, there are membrane proteins that are responsible for making sure that the calcium concentration in the ER goes back up. These proteins are called STIM proteins, and two types of these proteins are called STIM1 and STIM2. There is limited research on how STIM1 and STIM2 play into microglial response outside culture research, so I studied the role of STIM1 and STIM2 in microglial responses to a spinal cord injury in the cervical region. Modification of genes can be done through a method called Cre/loxP, where genetic modification can occur at a site of interest. Through this method, we were able to generate STIM1 knockout and STIM2 knockout mice as well as inducing tdTomato, a red fluorescent protein which allows the microglia in these mice to turn red when imaging on a confocal microscope. The results of the study found that there were discernible differences in microglial behavior between knockout and wildtype, or control, genotypes, in morphological changes which suggests that STIM1 and STIM2 may play a large role in inducing morphological changes in microglia following injury.

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