We used functional knockouts (by RNAi) and isolated gene knockouts of genes encoding peroxisomal proteins to evaluate the importance of various peroxisomal enzymes and peroxins for the development of Caenorhabditis elegans and to compare the roles of these proteins in the nematode to their roles in yeasts and humans. The nematode counterparts of the human ATP-binding cassette half-transporters, the enzymes alkyldihydroxyacetonephosphate synthase and delta3,5 -delta2,4 -dienoyl-CoA isomerase, the receptors for peroxisomal membrane and matrix proteins (Pex19p and Pex5p), and components of the docking and translocation machineries for matrix proteins (Pex13p and Pex12p) are essential for the development of C. elegans. Unexpectedly, RNAi silencing of the acyl-CoA synthetase-mediated activation of fatty acids, the alfa- and beta-oxidation of fatty acids, the intraperoxisomal decomposition of hydrogen peroxide, and the peroxins Pex1p, Pex2p and Pex6p had no apparent effect on C. elegans development. Knockouts of genes for peroxisomal catalase
ctl-2 (Y54G11A.5b) and for an ABC half-transporter (T02D1.5), an ortholog of human ALDP, have also been isolated. Whereas worms with the second gene knockout did not exhibit any noticeable phenotype, worms harboring the peroxisomal catalase gene knockout had a shortened lifespan. The described analysis provides a basis for the use of C. elegans as a valuable model system with which to study the molecular and physiological defects underlying the human peroxisomal disorders. Supported by the Alberta Heritage Foundation for Medical Research and the Canadian Institutes of Health Research.