Submitted to: Poultry Science
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2005
Publication Date: July 1, 2005
Citation: Richards, M.P., Poch, S.M., McMurtry, J.P. 2005. Expression of the proglucagon and companion receptor genes in chickens [abstract]. Poultry Science. 84(Supplement 1):55. Paper No. T43.
Expression of the proglucagon (PG) gene in mammals produces a single mRNA transcript that encodes glucagon and two glucagon-like peptide hormones (GLP-1 and GLP-2). Glucagon, GLP-1 and GLP-2 bind to specific receptors that are expressed in different tissues. These peptide hormones in conjunction with their receptors regulate various aspects of carbohydrate, lipid and amino acid metabolism. Additionally, the GLPs affect pancreatic insulin secretion, gastro-intestinal (GI) growth and function, and food intake. Our objectives were to investigate the structure and expression of the chicken PG gene and its companion receptor genes. We identified two distinct classes of PG mRNA (A and B) that were co-expressed in pancreas, proventriculus, duodenum, brain and liver. Both classes of PG mRNA share common sequence including a portion of the coding region (CDS) that contains glucagon and GLP-1. Class A mRNA lack the portion of the CDS that includes GLP-2, whereas class B mRNA have a larger CDS that includes GLP-2. Alternative splicing at the 3’ end of PG mRNA transcripts determines the class of mRNA produced. Both mRNA classes have unique 3’ untranslated regions that differ in size and sequence. Furthermore, each class of mRNA contains two variant forms arising from the incorporation of an alternate first exon. We also identified glucagon, GLP-1 and GLP-2 receptor gene transcripts. Specific RT-PCR assays were developed to determine individual mRNA levels in different tissues relative to 18S rRNA. In pancreas and proventriculus, class A mRNA was more highly expressed than class B. Glucagon receptor was most highly expressed in liver and abdominal fat; whereas, GLP-1 and GLP-2 receptor genes were highly expressed in GI tract, brain and pancreas. The chicken PG gene was sequenced and the mechanisms for producing multiple mRNA transcripts have been identified. We conclude that class A and B mRNA transcripts are produced from the chicken PG gene by alternative splicing that gives rise to unique 3’- and 5’- ends.