Germline mitochondria exhibit a distinct increase in Cytochrome c oxidase 1 expression relative to somatic cells in Caenorhabditis elegans Michael Eastwood1, James Priess1, 1Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, U.S.A.
Germ cells are totipotent cells integral to animal development. They exhibit remarkable regenerative capability and are the only cell type that can form gametes, such as sperm and oocytes, to maintain an immortal link between generations. We are exploring the composition and function of germ cell mitochondria in the nematode Caenorhabditis elegans, a prominent system for the study of germ cell biology. Germ cell mitochondria exhibit greatly increased expression of Cox1, the catalytic subunit of the cytochrome c oxidase complex. Germ cells display an increased ratio of Cox1 relative to other ETC components compared to other cell types, including closely neighboring cells of the somatic gonad. This expression difference is maintained through early embryonic development until the onset of zygotic mitochondrial biogenesis. Consistent with upregulation of Cox1 in germ cell mitochondria, we find cell lysates of early embryos that have germ cell-like mitochondria exhibit increased cytochrome c oxidase activity compared to lysates from whole animals at juvenile stages that have predominantly somatic mitochondria. Interestingly, embryonic lysates show lower levels of glycolytic activity, suggesting that germ cells do not maintain an increased global metabolic rate but rather have a preference for energy generation through mitochondrial respiration compared to glycolysis. Ongoing studies are focused on i) developing unbiased screens to uncover regulators of Cox1 expression in germ cells, ii) characterizing the stoichiometry and expression of other ETC components in germ cells and iii) exploring metabolic preferences of germ cells.
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