Developmental pattern of the expression of malonyl-CoA decarboxylase gene and the production of unique lipids in the goose uropygial glands.

The abundant fatty acid synthase in the uropygial gland of goose generates multimethyl-branched fatty acids as the major product because of the unique presence of the cytoplasmic malonyl-CoA decarboxylase which assures that only methylmalonyl-CoA is available to the synthase. If this conclusion is valid, the developmental pattern of expression of the gene for this tissue-specific decarboxylase should correlate with the appearance of other lipogenic enzymes and the production of the unique lipids. To test this possibility the levels of the decarboxylase, acetyl-CoA carboxylase, and fatty acid synthase in the gland of the embryonic and neonatal goose were measured by immunodiffusion and immunoblot assays for the proteins as well as the enzyme assays for the catalytic activities. Malonyl-CoA decarboxylase appeared several days before hatching as did the other two lipogenic enzymes and reached half-maximal levels by hatching. The levels of expression of the malonyl-CoA decarboxylase gene and cytoplasmic actin gene, which is not expected to be developmentally regulated, were measured by dot-blot analysis using cloned cDNA for the two proteins. The decarboxylase transcripts appeared 4 days prior to hatching and reached maximal levels by hatching, whereas the levels of cytoplasmic actin gene transcripts showed very little change. The appearance of oil droplets in the glands was clearly seen soon after hatching. These results show that malonyl-CoA decarboxylase gene expression is developmentally regulated in a manner consistent with its proposed role in the synthesis of the unique lipids of the uropygial gland.