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Frog diazepam-binding inhibitor: peptide sequence, cDNA cloning, and expression in the brain
I Lihrmann1, J C Plaquevent, H Tostivint
1European Institute for Peptide Research, Institut National de la Santé de la Recherche Médicale Unité 413, University of Rouen, Mont-Saint-Aignan, France.
Summary
Researchers identified three diazepam-binding inhibitor (DBI) peptides in frog brains, revealing conserved structure and glial cell expression across vertebrates. This highlights evolutionary conservation of DBI function.
Area of Science:
- Neuroscience
- Molecular Biology
- Evolutionary Biology
Background:
- Diazepam-binding inhibitor (DBI) is a neurosteroid precursor involved in various physiological processes.
- Understanding DBI's evolutionary conservation and tissue-specific expression provides insights into its fundamental roles.
Purpose of the Study:
- To isolate and characterize diazepam-binding inhibitor (DBI) peptides from the frog Rana ridibunda.
- To investigate the evolutionary conservation and expression patterns of DBI in a non-mammalian vertebrate model.
Main Methods:
- Peptide isolation and primary structure determination from frog brain.
- Screening of a frog brain cDNA library using degenerate primers.
- Northern blot analysis, in situ hybridization, and immunocytochemistry to study gene and protein expression.
Main Results:
- Three frog DBI peptides, homologous to mammalian DBI fragments, were isolated.
- Cloned cDNA revealed an 87-amino acid polypeptide with 68% similarity to mammalian DBI.
- DBI mRNA and immunoreactivity were highly expressed in the frog brain, particularly in ependymal cells and circumventricular organs, indicating selective glial cell expression.
Conclusions:
- The structure of DBI has been conserved throughout vertebrate evolution, suggesting fundamental importance.
- DBI is selectively expressed in glial cells in the frog brain, pointing to a specific role in these cells.
- These findings contribute to understanding the neurobiology and evolutionary history of DBI.