Submitted to: Biochimica et Biophysica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 12, 2006
Publication Date: November 1, 2006
Citation: Proszkowiec-Weglarz, M., Richards, M.P, McMurtry, J.P. 2007. Molecular cloning, genomic organization, and expression of three chicken 5'-AMP-activated protein kinase gamma subunit genes. Poultry Science. 85(11):2031-2041.
Interpretive Summary: Current strains of broiler chickens are the product of intensive genetic selection over many generations for rapid growth rate and enhanced meat yield. However, a number of unintended consequences have accompanied such genetic selection including the loss of coordinate regulation of feed consumption and energy balance. Thus, modern commercial broilers do not adequately regulate their voluntary food intake to meet specific energy needs to maintain a constant body weight. Instead, they are prone to overeating leading to excessive weight gain and energy accumulation (fattening) and a series of health-related problems such as obesity unless their food intake is strictly limited. Our overall objective is to identify those genes involved in the regulation of food intake and energy balance in the broiler chicken. The goal is to find and characterize candidate genes that can be used as potential selection markers to improve feed intake, energy balance and meat production traits in commercial poultry flocks. In this report we identified and characterized three genes that code for proteins that are part of the enzyme complex, 5'-AMP-activated protein kinase (AMPK). AMPK serves as an energy status monitor and regulator that affects food intake and energy balance in animals and humans. Specifically, we have, for the first time, identified and characterized three gamma subunit isoform encoding genes in the broiler chicken and determined in which tissues these three genes are functioning. We now know that the gamma subunit of the AMPK enzyme complex performs the important role of 'energy sensor'. Knowledge about gamma subunit isoform gene structure and expression in chickens is key to understanding how AMPK influences food intake and energy balance. Because AMPK represents a possible molecular link between food intake regulation and maintenance of energy balance, finding and characterizing these genes in chickens provides researchers with new information that can be used to further define the genetic basis for this important physiological relationship in poultry.
In this study we characterized the genomic organization and expression of three chicken 5'-AMP-activated protein kinase gamma subunit (cPRKAG) genes. A molecular cloning strategy involving a combination of primer-directed RT-PCR and 5'-RACE was developed to sequence cDNAs corresponding to the complete coding regions and portions of the 5'- and 3'-untranslated regions of cPRKAG1, cPRKAG2 and cPRKAG3 mRNA transcripts. Alternative splicing of the second exon of the cPRKAG1 gene resulted in two transcript variants that code for predicted proteins of 298 and 276 amino acids. Use of an alternate transcription initiation site with an alternate promoter and/or alternative splicing resulted in four different transcript variants of the cPRKAG2 gene that code for predicted proteins of 567, 452, 328 and 158 amino acids. Alternative splicing of exon 3 in the cPRKAG3 gene resulted in the production of 'long' and 'short' transcript variants that code for predicted proteins of 382 and 378 amino acids, respectively. We found evidence for differential expression of individual gamma subunit gene transcript variants and in some cases tissue-specific expression was observed. Chicken AMPK gamma subunit genes displayed similar structural features and high sequence homology compared to corresponding mammalian gamma subunit gene homologues.