Genetic dissection of polyunsaturated fatty acid synthesis in Caenorhabditis elegans - PubMed (original) (raw)

Genetic dissection of polyunsaturated fatty acid synthesis in Caenorhabditis elegans

Jennifer L Watts et al. Proc Natl Acad Sci U S A. 2002.

Abstract

Polyunsaturated fatty acids (PUFAs) are important membrane components and precursors of signaling molecules. To investigate the roles of these fatty acids in growth, development, and neurological function in an animal system, we isolated Caenorhabditis elegans mutants deficient in PUFA synthesis by direct analysis of fatty acid composition. C. elegans possesses all the desaturase and elongase activities to synthesize arachidonic acid and eicosapentaenoic acid from saturated fatty acid precursors. In our screen we identified mutants with defects in each fatty acid desaturation and elongation step of the PUFA biosynthetic pathway. The fatty acid compositions of the mutants reveal the substrate preferences of the desaturase and elongase enzymes and clearly demarcate the steps of this pathway. The mutants show that C. elegans does not require n3 or Delta5-unsaturated PUFAs for normal development under laboratory conditions. However, mutants with more severe PUFA deficiencies display growth and neurological defects. The mutants provide tools for investigating the roles of PUFAs in membrane biology and cell function in this animal model.

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Figures

Figure 1

Figure 1

Mutations in the fat-1 gene result in the loss of n3 PUFA. GC traces of populations of worms of the following genotypes: +/+, WT; fat-1/+, segregating population consisting of WT, fat-1 heterozygotes, and fat-1 homozygotes; and fat-1/_fat-_1, fat-1 homozygotes. 17:Δ, 9,10-methylene hexadecanoic acid; 19:Δ, 11,12-methylene octadecanoic acid.

Figure 2

Figure 2

Mutations in fatty acid desaturase and elongase ORFs. The predicted amino acid change for each mutant allele is noted.

Figure 3

Figure 3

C. elegans mutants deficient in PUFA synthesis. Partial GC traces of populations of WT (A) and PUFA mutant (B_–_F) worms. The alleles used were as follows: fat-1(wa9), fat-2(wa17), fat-3(wa22), fat-4(wa14), and elo-1(wa7). For comparison of growth, 2-fold stage embryos from each genotype were placed onto culture plates, incubated at 20°C, and photographed after 72 h of growth. At this point WT, fat-1, fat-4, and elo-1 worms had reached adulthood and were just starting to lay eggs, whereas fat-3 had reached the L4 larval stage and fat-2 had grown only to the L2 larval stage. 19:Δ, 11,12-methylene octadecanoic acid.

Figure 4

Figure 4

The pathway of PUFA synthesis in C. elegans. Horizontal or slanted arrows represent fatty acid desaturation. Vertical arrows represent fatty acid elongation. For the desaturation steps, the desaturase activity is noted above the arrow, and the C. elegans gene encoding this enzymatic activity is listed below the arrow.

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