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Paluri, Sravya

University of British Columbia

In Drosophila, permeability barriers maintain homeostasis and ensure proper functioning of different tissues. In the nervous system, the blood-brain/nerve barriers are crucial for neuronal function and for survival. A type of glial cell, subperineurial glia (SPG) forms these barriers in both the central and the peripheral nervous system. Neighboring SPG cells form septate junctions (SJs) to seal the barrier at the bicellular contact points and, along the contact point of three cells, tricellular junction (TCJ). To maintain barrier integrity, the proper development of SPG, the SJ and the TCJ structure are crucial however, the mechanisms involved in coordinating this process are unknown. We hypothesized that microRNAs might be playing a role in SPG development and in SJ and TCJ formation. In Chapter 2, we performed a genetic screen using microRNA-sponges to knockdown 120 microRNAs in SPG and analyzed SPG morphology. We found that the knockdown of only microRNA-125 resulted in SPG morphological defects. However, our verification analysis using a microRNA-125 knockout mutant exhibited no morphological defects, suggesting that our genetic screen resulted in false positive results in SPG. In Chapter 3, we found that the SJ proteins Kune-kune, Sinuous and Macroglobulin-complement related are present in glial SJ, and Gliotactin, Bark and M6 are present in glial TCJ. Additionally, we found that overexpression of microRNA-184 (known to regulate SJ and TCJ proteins) led to the disruption of SJ structure and affected the localization of SJ proteins but had no effect on TCJ protein localization. We hypothesized that these phenotypes might be attributed to microRNA-184 binding to its target SJ and TCJ mRNAs and lowering their levels. However, using qRT-PCR technique, we found that the mRNA levels of these proteins were unaffected, suggesting that microRNA-184 binds to target SJ proteins and translationally repress them. Overexpression of miR-184 led to larval locomotory defects and lethality with a compromised blood-brain barrier. Thus, microRNAiv 184 overexpression in SPG disrupts the SJ structure and compromises the barrier function. Overall, we found that microRNAs might not play a role in peripheral glial development but are crucial for regulation of the permeability barrier in glia.

Text

2024-02-13

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87428

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/