2004 West Coast Worm Meeting abstract 253
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Institute of Biological Chemistry, Washington State University, Pullman, WA 99164
Monounsaturated fatty acids (MUFAs) play many important roles in an organism.
They are incorporated into lipids such as membrane phospholipids where they influence membrane fluidity and triacylglycerols where they influence lipoprotein metabolism and adiposity. MUFAs are also the precursors to polyunsaturated fatty acids, which are also important in membrane function as well as cell signaling. MUFAs are a significant fraction of the fatty acids in C. elegans, a valuable model animal for studying fatty acid metabolism as they synthesize all of the fatty acids required for their survival. In C. elegans, synthesis of MUFAs is dependent on the activity of a family of three D9 desaturases, encoded by fat-5, fat-6 and fat-7. These desaturases introduce a double bond between the 9th and 10th carbons in 16- and 18-carbon fatty acids, the preferred substrates. The D9 desaturase, as the rate-limiting step for creation of MUFAs is, therefore, highly regulated. Expression of gene::GFP fusions show that fat-5, fat-6 and fat-7 are expressed in the intestine with additional fat-6 expression seen in the hypodermis and fat-5 expression seen in the pharynx. In order to determine the precise roles of each desaturase, we have obtained knockouts of the three C. elegans D9 desaturases. Single mutants show only subtle fatty acid composition changes and no other obvious phenotypes. Double mutant combinations, however, show reduced viability under conditions of stress, such as low temperature and starvation. Further study will continue to provide information about fatty acid metabolism, maintenance of membrane fluidity, and fat storage.