Molecular and Functional Characterization of Genes in and Pointing to a Critical Role in Very Long-Chain (>C) Fatty Acid Synthesis during Early Neural Development of Fish.

Very long-chain fatty acids (VLC-FA) play critical roles in neural tissues during the early development of vertebrates. However, studies on VLC-FA in fish are scarce. The biosynthesis of VLC-FA is mediated by elongation of very long-chain fatty acid 4 (Elovl4) proteins and, consequently, the complement and activity of these enzymes determines the capacity that a given species has for satisfying its physiological demands, in particular for the correct development of neurophysiological functions. The present study aimed to characterize and localize the expression of genes from and , as well as to determine the function of their encoded proteins. The results confirmed that both fish possess two distinct genes, named and . Functional assays demonstrated that both Elovl4 isoforms had the capability to elongate long-chain (C), both saturated (SFA) and polyunsaturated (PUFA), fatty acid precursors to VLC-FA. In spite of their overlapping activity, Elovl4a was more active in VLC-SFA elongation, while Elovl4b had a preponderant elongation activity towards n-3 PUFA substrates, particularly in , being additionally the only isoform that is capable of elongating docosahexaenoic acid (DHA). A preferential expression of genes was measured in neural tissues, being and mRNAs mostly found in brain and eyes, respectively.