IAPs are constitutively expressed in pancreatic beta-cells of certain diabetes-susceptible inbred mouse strains, and increase in response to hyperglycemic stress induced by the db gene in homozygous state. The difference in expression of IAP genes in islet cells of mice susceptible and resistant to induction of diabetes by the db gene provides a useful system in which to examine control of IAP element expression. Sequencing of pancreatic beta-cell IAP cDNAs showed that five clones had identical sequences, suggesting that a major IAP transcript, derived from one or a number of identical genes, is present in these cells. In contrast, betaTC cells, an established mouse cell line derived from a beta-cell tumor, expressed a variety of IAP elements. An oligonucleotide probe specific for the IAP element expressed in pancreatic beta-cells detected a subset of the total IAP elements with their flanking sequences in genomic DNA. Among these were two fragments in the DNA of a diabetes susceptible strain of mouse that were not present in a diabetes resistant strain. This probe will be used to determine whether there is a difference in genomic location of these IAP elements in the two strains.
