Seabream Ghrelin Gene Uncovered: Insights into Fish Appetite Regulation

Ghrelin is a crucial peptide hormone primarily known for its role as a "hunger hormone," stimulating appetite and promoting fat storage in mammals. It also influences growth hormone release and metabolism. While well-understood in terrestrial vertebrates, the specific genetic makeup and regulatory mechanisms of ghrelin in diverse aquatic species, particularly the seabream, remained largely unexplored. This study aimed to characterize the ghrelin gene in seabream at a molecular level.

The study successfully identified and characterized the seabream ghrelin gene. They found that seabream ghrelin cDNA encodes a 117-amino acid preproghrelin precursor, which includes the mature 28-amino acid ghrelin peptide. The genomic organization revealed that the seabream ghrelin gene spans approximately 3.5 kb and consists of 5 exons and 4 introns, a structure largely conserved with other vertebrate ghrelin genes. Sequence analysis showed the seabream ghrelin peptide shares 78% amino acid identity with tilapia ghrelin and 65% with human ghrelin, particularly in the N-terminal octapeptide region crucial for biological activity. Furthermore, they observed 2.3-fold higher ghrelin mRNA expression in the stomach compared to the brain. The promoter region analysis identified several putative regulatory elements, including binding sites for GHF-1 (growth hormone factor 1) and Sp1, suggesting complex transcriptional control.