Cloning, molecular characterization, and nutritional regulation of fatty acid-binding protein family genes in gold pompanos (Trachinotus ovatus).

Fatty acid-binding protein (Fabp) is an important protein family involved in fatty acid uptake and deposition. Elucidating the function and regulation of fabps could contribute to the efficient production of biologically relevant fatty acids, such as highly unsaturated fatty acids (HUFAs), from fish. Herein, five genes from Trachinotus ovatus named fabp4, fabp6a, fabp6b, fabp7a, and fabp7b coding 133, 127, 118, 132, and 132 amino acid residues were cloned and sequenced. The effect of dietary HUFA on the expression of these genes was also investigated. Multiple protein sequence alignment showed that these Fabps shared high identity to their orthologs from other fish and mammals. Two conserved domains, lipocalin and lipocalin 7, were predicted in the deduced protein sequence of fabp4 and fabp7 paralogs, whereas fabp6 paralogs did not present the lipocalin domain. The adipose tissue, spleen, gill, and intestine showed the highest levels of fabp6b expression. In the brain, fabp6b was weakly expressed, whereas the expression of fabp7a was at its highest. Conversely, fabp7a showed a lower mRNA level than the other fabps in the liver and heart. In the dorsal muscle and kidney, fabp6a was the most abundantly expressed gene. Increasing dietary HUFA from 1.0% to 2.1% increased the gene expression of hepatic fabp4 and fabp6a gene expression but decreased gene expression in the dorsal muscle. Similarly, the expression of fabp7a in the dorsal muscle also declined in the 2.1% HUFA group. This study lays the groundwork for further studies focused on the physiological function and regulation of fish fabps.