Submitted to: International Symposium on Avian Endocrinology Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: April 11, 2008
Publication Date: July 11, 2008
Citation: Richards, M.P., McMurtry, J.P. 2008. Expression of proglucagon and proglucagon-derived peptide hormone receptor genes in the chicken [abstract]. In: Proceedings of the Ninth International Symposium on Avian Endocrinology. Abstract Number S4.
To better understand how the glucagon system functions in birds, we utilized a molecular cloning strategy to sequence and characterize the chicken proglucagon gene. This gene has seven exons and six introns with evidence for an additional (alternate) first exon and two promoter regions. Two classes of proglucagon mRNA transcripts (PGA and PGB), produced by 3’-end alternative splicing, were co-expressed in all tissues examined with pancreas and proventriculus showing the highest levels. Although both mRNA classes contained coding sequence for glucagon and GLP-1, PGA lacked sequence for GLP-2 that was included in PGB. Both PGA and PGB exhibited two variants, each with a different 5’-end arising from alternate promoter and alternate first exon usage. Fasting and refeeding had no effect on proglucagon mRNA expression despite significant changes in plasma glucagon levels. To investigate potential differences in proglucagon precursor processing among tissues, mRNA expression for two prohormone convertase (PC) genes was analyzed. PC2 mRNA was predominantly expressed in pancreas and proventriculus, whereas PC1/3 mRNA was more highly expressed in duodenum and brain. We also determined mRNA expression of the specific receptor genes for glucagon, GLP-1 and GLP-2 to help define major sites of hormone action. Glucagon receptor mRNA was most highly expressed in liver and abdominal fat, whereas GLP-1 and GLP-2 receptor genes were highly expressed in the gastrointestinal tract, brain, pancreas and abdominal fat. Our results offer new insights into structure and function of the chicken proglucagon gene, processing of the precursor proteins and potential activity sites for proglucagon-derived peptide hormones mediated by their receptors.