Investigating the Dynamic Nature of Mitochondrial Networks in C. Elegans

Download or read book Investigating the Dynamic Nature of Mitochondrial Networks in C. Elegans written by Saroj G. Regmi and published by . This book was released on 2015 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mitochondria are dynamic organelles that undergo constant fusion and fission events and this dynamic homeostasis defines the overall morphology of a mitochondrial network. Although these fusion and fission events are important for the maintenance of mitochondrial function, the physiological role of these processes remains poorly characterized. Using the nematode C. elegans as a model organism, this thesis explores various aspects of mitochondrial dynamics by: (i) examining its role in the context of aging; (ii) investigating the localization of CED-9, a Bcl-2-family member and regulator of mitochondrial dynamics; and finally, (iii) developing tools to study mitochondrial dynamics. Using transgenic animals expressing a matrix-targeted GFP under the control of a muscle-specific promoter (P[subscript myo-3] mitoGFP), I observed that body-wall muscles display a tubular inter-connected mitochondrial network that fragments with increasing age. Therefore, I aimed to determine if mitochondrial morphology is a suitable bio-marker of aging. To that end, I analyzed various aspects of mitochondrial morphology (e.g. mitochondrial length, circularity, area) in animals raised at different temperatures. I found that in animals grown at 15°C, the onset of mitochondrial fragmentation occurred later in life than those animals grown at 25°C. Furthermore, I analyzed mitochondrial morphology in both short- and long-lived animals. To complement this analysis, I characterized mitochondrial morphology in five- and seven-day old animals to determine if those displaying a fragmented mitochondrial morphology exhibit shorter lifespans when compared to animals displaying tubular mitochondrial morphology. The results suggest that while mitochondria in body-wall muscles undergo age-dependent fragmentation and a loss in volume, these changes are not a cause of aging but rather a consequence of the aging process. Using super-resolution microscopy, I investigated whether CED-9 localizes not only to mitochondria but also to the ER. Data collected from this study indicate that a subpopulation of CED-9 is dually localized to mitochondria and the ER. This may be important for the maintenance of ER-mitochondria contact. Finally, I describe the generation of fluorescent markers, including a photo-convertible DENDRA-based construct, as a means to study aspects of mitochondrial dynamics. Collectively, these represent valuable tools for the study of mitochondrial fusion and fission, as well as mitophagy.