Fission, fusion and distribution of mitochondria in mammalian cells

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Mitochondria are small cellular compartments that produce most of the cell's energy in the form of ATP. Mitochondria were once thought of as small bean-shaped organelles floating around in the cell, however it has become clear that this is not the case. Mitochondria are found as a network of tubules radiating from around the nucleus and they undergo constant changes in their shape through both fission and fusion events. Mitochondria are transported along microtubules which act as highways in the cell so that they can be distributed to areas that require ATP or other functions particular to mitochondria such as their ability to regulate the release of calcium. In specialist cells, mitochondria are organised even further. Sperm cells contain mitochondria packed around the mid-piece of the flagellum so that ATP can be utilised directly for swimming. Mitochondria are also highly organised in muscle cells to supply ATP for movement while in pancreatic cells mitochondria at the cell's edge help to regulate the secretion of molecules such as insulin into the bloodstream. While we are beginning to understand the great importance of mitochondria to the cell, we are yet to work out how these organelles undergo the drastic morphological changes which are essential for cellular function. In this application, we plan to identify and characterise the proteins involved in the division of mitochodria and the movement of these organelles along the microtubule highways. Understanding the basic mechanisms of mitochondrial dynamics in tissue culture cells will provide valuable insights into mitochondrial segregation and specialisation in differentiated cells such as sperm, nerve, muscle and pancreatic cells, where such events are crucial for function.