Characterization of melanocortin 4 receptor in Snakeskin Gourami and its expression in relation to daily feed intake and short-term fasting

In this study, melanocortin 4 receptor (MC4R) was characterized in Snakeskin Gourami (Trichogaster pectoralis) and designated as TpMC4R. The TpMC4R contained predicted regions that were structural features of MC4R subtypes of vertebrates. In addition, phylogenetic analyses showed that TpMC4R were in MC4R orthologues and closely related to piscine MC4Rs. The TpMC4R transcripts were detected in embryos at all developmental stages. Further, its mRNA was detectable in unfertilized eggs, suggesting that TpMC4R could be classified as maternal mRNA. Using real-time RT-PCR, graded expression at each central and peripheral tissue was demonstrated. Localization of TpMC4R expression in the brain was performed by in situ hybridization. An experiment was conducted to determine the expression profile of TpMC4R during daily feeding in each region of the brain. Fish were fed twice a day at 10:00 and 16:00, and the level of TpMC4R expression was analyzed at 9:00, 11:00, 13:00 and 15:00. The expression level of TpMC4R was significantly reduced at 15:00 compared to that at all previous times (9:00, 11:00 and 13:00). Moreover, significantly higher expression levels of TpMC4R were observed at 18- and 24-h fasting periods. The finding of variation in MC4R expression level during daily feeding and fasting period revealed some direct and/or indirect relations of the MC4R expression to circadian feeding rhythm and short-term food deprivation in fish.

► Characterization of melanocortin 4 receptor of Snakeskin Gourami. ► MC4R expression during embryogenesis of Snakeskin Gourami. ► Expression level of MC4R in central and peripheral tissues of Snakeskin Gourami. ► Neuronal expression profiles of MC4R during daily feed regimen in Snakeskin Gourami. ► Effect of short-term fasting on neuronal expression of MC4R in Snakeskin Gourami.