Alternative transcripts of fatty acid desaturase (FADS) genes.

Alternative splicing is a major mechanism for increasing the range of products encoded by the genome. We recently reported positive identification of the first alternative transcripts (AT) of fatty acid desaturase 3 (FADS3) and FADS2 in fetal and neonatal baboons. FADS3, a putative polyunsaturated fatty acid (PUFA) desaturase gene with no known function, has 7 AT that are expressed in at least twelve organs in an apparently constitutive manner. At least five of seven AT are expressed in several mammals and the chicken. FADS2, catalyzing 6 and 8 desaturation and having multiple PUFA substrates, has one AT that is missing two exons and portions of two others. Semi-quantitative expression estimates reveal at least 20-fold differential expression of FADS2 AT1 among neonatal baboon organs compared to 2-fold in the same organs for the classically spliced (CS) FADS2 transcript. Expression of four of the FADS3 AT, those with missing putatively active domains, is highly correlated among organs, suggesting coordinated coexpression. AT may serve as templates to generate protein isoforms or as signaling molecules, and their widespread detection and expression patterns suggest that they play an important role in PUFA biosynthesis.