Author
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Richards, Mark |
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Poch, Stephen |
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Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/14/2003 Publication Date: 12/1/2003 Citation: Richards, M.P., Poch, S.M. 2003. Molecular cloning and expression of the turkey leptin receptor gene. Comparative Biochemistry and Physiology 136:833-847. Interpretive Summary: Poultry producers have, over the years, intensively selected for lines of chickens and turkeys that grow faster and produce more meat than previous generations. Unfortunately, along with these improvements have come some unintended changes in feed intake and body composition. Modern commercial strains of chickens and turkeys tend to overeat, making them prone to obesity and other health problems related to excessive fattening due to increased feed consumption. Therefore, it is important to understand, at the genetic level, the regulatory mechanisms for controlling feed intake and energy balance in poultry. One component of this regulatory system involves the hormone leptin and its specific receptor. By binding to its receptor, leptin induces a cascade of cellular responses that culminate in appetite reduction and increased energy expenditure leading to reduced levels of fat and ultimately a decrease in body weight. An important key to understanding this complex process is learning about the structure and function of the leptin receptor and the gene that encodes this important protein. This work describes our efforts to identify and characterize the leptin receptor gene in turkeys and to determine some of the unique characteristics of the protein product of this gene. We also investigated the activity of this gene in different tissues at different stages of development to try and determine potential sites of action for leptin in poultry. This information will be useful to researchers studying the control of appetite and body weight in avian species, as well as, producers in formulating new genetic selection and feeding strategies for commercial poultry flocks. Technical Abstract: A cDNA encoding the long form of the turkey (Meleagris gallopavo) leptin receptor (LEPR) gene was cloned and sequenced. Turkey LEPR showed greater than 90% sequence identity at both the nucleotide and amino acid level with chicken LEPR. The LEPR gene (long form) codes for a protein of 1147 amino acids that has a number of features similar to other LEPRs including: a signal peptide, a single transmembrane domain, and specific conserved motifs defining putative leptin-binding and signal transduction regions of the protein. In addition, a LEPR gene-related protein (LEPR-GRP) mRNA transcript was also identified and the corresponding cDNA sequenced. The turkey LEPR-GRP gene encodes a 14 kDa (131 amino acids) protein that is distinct from LEPR. LEPR gene expression was quantified relative to b-actin in total RNA samples isolated from various tissues of 3 wk old turkey poults. Expression of LEPR was highest in brain, spleen and lung tissue with lower levels of expression in kidney, pancreas, duodenum, liver, fat, and breast muscle. In developing turkey embryos, expression of LEPR was higher in brain tissue throughout incubation (days 14-28). Expression of LEPR in embryonic liver tissue peaked at day 16 and then declined toward hatching (day 28). Yolk sac expression of LEPR declined from day 14 to day 20 and then increased toward hatching. Our findings suggest differential regulation of LEPR and LEPR-GRP expression in turkey tissues during embryonic and post-hatch development. In conclusion, this is the first report to characterize LEPR and LEPR-GRP gene homologues in the domestic turkey. |
