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Proglucagons in vertebrates: Expression and processing of multiple genes in a bony fish
Ellen R Busby1, Thomas P Mommsen1
1Department of Biochemistry and Microbiology, and Department of Biology, University of Victoria, Victoria, BC, Canada.
Summary
Copper rockfish possess two distinct proglucagon genes, leading to varied peptide production. This complex gene regulation suggests unique roles for these glucagon-like peptides in fish.
Area of Science:
- Comparative endocrinology
- Molecular biology
- Fish physiology
Background:
- Mammals have one proglucagon (PG) gene, producing glucagon, GLP-1, and GLP-2.
- Many non-mammalian vertebrates possess multiple PG genes, indicating evolutionary divergence.
Purpose of the Study:
- Investigate proglucagon mRNA sequences, tissue expression, and peptide processing in a diploid bony fish.
- Characterize the complexity of PG gene regulation and its products in copper rockfish (Sebastes caurinus).
Main Methods:
- Analysis of proglucagon mRNA sequences from copper rockfish.
- Tissue expression profiling (endocrine pancreas, brain, gastrointestinal tract).
- Mass spectrometry for peptide identification and processing analysis.
Main Results:
- Copper rockfish express two distinct PG genes (PG I, PG II), with PG II lacking GLP-2.
- Differential transcription observed across various tissues.
- Alternative splicing and differential processing generate multiple glucagon and GLP-1 variants, and a single GLP-2.
- Mass spectrometry confirmed translation of both PG transcripts and differential peptide processing.
Conclusions:
- The presence of two PG genes and complex regulation suggests unique, unidentified roles for their peptide products in fish.
- Differential regulation of PG genes and their products highlights evolutionary adaptations in non-mammalian vertebrates.
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