Introductory overview by HIROSHI OKAMOTO

Summary

Recent advances in molecular biology have made it possible to study the structure and function of the genes that encode the peptide hormones. Among the best characterized of these are insulin, glucagon, somatostatin and pancreatic polypeptide, all of which are produced in a multiendocrine organ, the islet of Langerhans. In addition, an explanation at the molecular level of the principal pathological condition associated with this organ, insulin-dependent diabetes, is now possible.

In the first section of this volume, a full account is offered of state-of-the-art thinking on islet hormone biosynthesis. The second section is devoted to an examination of the effects of deleterious agents and conditions on the functioning of islet cells, particularly of islet B-cells, which produce insulin.

The molecular biology of peptide hormones in islets of Langerhans

Understanding the structure, organization and expression of the genes that encode insulin, glucagon, somatostatin, pancreatic polypeptide, vasoactive intestinal peptide and pancreastatin (Chapters 1, 2, 4, 5, 6, 7 and 8) has been made possible by the cloning and sequencing of both cDNAs and genomic sequences for these genes. From these sequences, the precise amino acid sequences of the peptide precursors have been deduced. In addition, from the genomic clones, it has been possible to map the exons (the encoding sequences) with respect to the introns (the intervening, non-encoding sequences). Finally, cis-acting regulatory sequences that flank the structural genes have been identified, as have, in part, trans-acting factors that interact with the cis-acting sequences.