McDonald Lab Graduate Students

Divyang Patel

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Each cell contains different organelles. For example, the nucleus coordinates the cell’s functions and duplicates DNA. The Golgi body folds proteins. The mitochondrion is the powerhouse of the cell – it provides the energy needed for all of the cell’s activities. We study the alternative oxidase gene and its potential use in treating mitochondrial (mito) diseases. Mito diseases include Parkinson’s, Huntington’s and multiple sclerosis. They affect about 1 in 5000 people and there are no effective cures.

Energy is produced through the electron transport chain of the mitochondria. Imagine an assembly line with 5 employees stationed through it. The first employee might paint the product, and then transfer it down the line to the next employee, who may label it, and so on, until the finished product is made. In a similar way, electrons are transferred through the first 4 complexes of the electron transport chain (see figure below). At the same time, protons are transferred across the membrane and used by the fifth complex to make ATP, which is the energy of the cell. Now, if any of the employees in the assembly line were sick or did not show up for work, the product would not be properly made. Similarly, if there are mutations in any of the 5 complexes of the electron transport chain, energy production is compromised.

So you can imagine how this would affect the cell, and indeed the whole body. Without sufficient energy, muscles and bones do not develop, neurons cannot carry out their functions, and the body generally wastes away. These are exactly the symptoms in patients with mito diseases, the majority of whom are infants and children. Mito diseases also affect the elderly, and we all know of loved ones who suffer from Alzheimer’s, dementia and ALS.

Our research aims to treat some of these mito diseases with the use of the alternative oxidase gene. This is an ‘alternative’ complex in the electron transport chain – imagine it as a backup employee in the assembly line. When complex III or IV is not working, electrons can still be accepted by the alternative oxidase and some energy is produced. We are using an animal alternative oxidase gene and expressing it in yeast. The yeast have mutations in complexes III and IV and so model many human mito diseases. We hope to show that these genetically modified yeast are able to survive due to the presence of the alternative oxidase. Perhaps in the not too distant future, alternative oxidase can be used as gene therapy for patients suffering from mito diseases.

Hillary Peon

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Hi, I’m Hillary and I started my Masters in Biology at Laurier in May 2015. Throughout my undergraduate degree I found my passion to be plant biology specifically the area of stress physiology. My project focuses on the mechanism and production of variegation in plants. Most plants are green in colour which is due to the chlorophyll in their chloroplasts. Variegation is the production of this normal green colour but also an abnormal white colour that appears in sections on a plant’s leaves, stems and even fruits. Variegation was discovered through genetic manipulation of a protein involved in photosynthesis called Plastoquinol Terminal Oxidase, or PTOX. This protein is very useful during the beginning stages of the plant’s life cycle because it helps to protect photosynthesis from damage. Genetically mutating PTOX not only stops photosynthesis from producing sugars for the plant but also stops another pathway called the carotenoid biosynthesis pathway. This is another important pathway as it makes pigments that protect the photosynthetic proteins. When the carotenoid pathway stops a white product called phytoene starts to accumulate in the chloroplasts. Over time phytoene becomes noticeable on the plant’s leaves and this is indicates variegation is occurring.

My work involves manipulating PTOX through chemical inhibition rather than genetic mutation to produce variegation. Researching this topic will allow for a better understanding of photosynthesis as it is an important interconnected pathway.

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