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Elasmobranchs express separate cholecystokinin and gastrin genes
A H Johnsen1, L Jonson, I J Rourke
1Department of Clinical Biochemistry, Rigshospitalet (National University Hospital), Copenhagen, Denmark. johnsen@rh.dk
Summary
Researchers identified distinct cholecystokinin (CCK) and gastrin peptides in sharks, pushing back the evolutionary divergence of the CCK/gastrin family to at least 350 million years ago.
Area of Science:
- Evolutionary biology
- Comparative genomics
- Endocrinology
Background:
- The cholecystokinin (CCK)/gastrin peptide family is crucial in vertebrate physiology.
- Gastrin was thought to be exclusive to higher vertebrates, with CCK considered the ancestral form.
Purpose of the Study:
- To investigate the evolutionary origins of the CCK/gastrin family in cartilaginous fishes.
- To trace the divergence of CCK and gastrin genes and peptides beyond known vertebrate groups.
Main Methods:
- Peptide identification in two shark species: spiny dogfish (Squalus acanthias) and porbeagle (Lamna cornubica).
- Isolation and sequencing of CCK and gastrin genes and cDNAs from the spiny dogfish.
- Comparative sequence analysis of deduced prepropeptides across various vertebrate species.
Main Results:
- Distinct CCK and gastrin peptides were identified in both shark species.
- Shark CCK and gastrin genes and peptide structures show significant conservation.
- Sequence similarities in dogfish prepropeptides support a common ancestral origin for the CCK/gastrin family.
Conclusions:
- The CCK/gastrin family segregation predates or coincides with the evolution of cartilaginous fishes, at least 350 million years ago.
- This divergence likely occurred alongside the emergence of gastric acid secretion in early vertebrates.