Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2006
Publication Date: 8/9/2006
Citation: Coulibaly, I., Gahr, S.A., Palti, Y., Yao, J., Rexroad III, C.E. 2006. Genomic structure and expression of uncoupling protein 2 genes in rainbow trout (oncorhynchus mykiss). Biomed Central (BMC) Genomics 7:203.
Interpretive Summary: In living cells, most of the energy is produced in mitochondria through the process of oxidative phosphorylation. In this process, the high energy molecule ATP is synthesized by combining ADP and Pi molecules. Uncoupling proteins (UCPs), are capable of reducing the efficiency of this ATP synthesis process to generate heat. The archetypical UCP1 is expressed in brown adipose tissue of mammals and is involved in non-shivering thermogenesis. UCP1 mRNA has recently been found in ectothermic organisms such as carp, zebrafish and pufferfish . Homologues of UCP1 (UCP2, 3, 4, 5) have been identified from various tissues in vertebrates and plants. The present study was designed to identify and characterize UCP2 genes in rainbow trout and investigate their roles in traits associated with energy balance and nutrition. To this end, we identified two UCP2 genes based on comparisons of DNA sequences with other organisms. We observed the tissues where they function and examined their expression patterns in muscle from fry responding to fasting.
Technical Abstract: Uncoupling proteins (UCPs) are anion transporters of the inner mitochondrial membrane that dissociate the respiratory chain from ATP synthesis. We report the first characterization of UCPs in rainbow trout (Oncorhynchus mykiss). Two UCP2 genes were identified, UCP2A and UCP2B. These genes are 93% similar in their predicted amino acid sequences and display the same genomic structure (8 exons and 7 introns) spanning 4.2 kb and 3.2 kb, respectively. UCP2A and UCP2B were widely expressed in all tissues of the study with a predominant level in macrophage-rich tissues and reproductive organs. In juvenile fish muscle we observed an increase in UCP2B expression in response to fasting and a decrease after refeeding in agreement with previous studies in human, mouse, rat, and marsupials. The converse regulatory pattern was observed for UCP2A mRNA which decreases during fasting, suggesting differential metabolic roles for UCP2A and UCP2B in rainbow trout muscle. Phylogenetic analysis including other genes from the UCP core family located rainbow trout UCP2A and UCP2B with their orthologs and suggested an early divergence of vertebrate UCPs from a common ancestor gene.