Cloning and over-expression of a masu salmon (Oncorhynchus masou) fatty acid elongase-like gene in zebrafish

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are particularly important n−3 highly unsaturated fatty acids (HUFA) for humans, and are generally obtained from a diet of marine fish captured in the wild. Farmed fish could well be a significant source if they are able to synthesize these fatty acids. It may be possible to improve the ability of these fish to produce the HUFA through bioengineering. We isolated an elongase-like gene (MELO) from masu salmon and over-expressed it in zebrafish to modify its HUFA metabolic pathway for increasing EPA and DHA production. The full-length MELO transcript encoded a polypeptide of 295 amino acids, containing motifs conserved among known elongases and sharing sequence identity with previously identified polyunsaturated fatty acid elongases. Expression of this gene in transgenic fish fed Artemia helped improve their EPA content by 1.30-fold and DHA by 1.33-fold, compared with non-transgenic fish. In contrast, the octadecatetraenoic acid content decreased, it being a substrate of elongase, while total lipids remained constant. This amply illustrates that MELO was functional in zebrafish and was able to alter its HUFA biosynthetic pathway, and also suggests that this technology could possibly be used to modify farmed fish as a nutritionally-richer product for human consumption.