mouse strain STOCK Pdx1{tm1Macd}/J mouse strain A mouse strain in which the targeted gene, Pancreatic and duodenal homeobox 1 (NCBI Gene ID: 18609), has been modified (allele type: Gene Replacement) to targeted mutation 1 (MGI ID: Pdx1{tmd1Macd}). Mice homozygous for the targeted mutation fail to develop a pancreas. Heterozygous mice have normal pancreatic development, but have partially impaired glucose tolerance in adulthood. The substitution of the targeted Ipf1/Pdx1 gene with tTAoff inactivates the endogenous allele and places tTAoff expression under the control of the endogenous transcriptional regulatory sequences of the Pdx1 locus. Identical to the endogenous allele, mutant locus expression is detectable in the pancreas and adjacent duodenum but not in other visceral organs or salivary glands. This mutant may be useful to direct tetracycline-regulated expression of responder transgenes in studies of pancreatic endocrine/exocrine development and function and diabetes. This mutant can also be bred with other tetO/TRE strains for pancreas-specific applications. This mutant was originally designed to be mated with mice engineered with a heptameric tetracycline operator (tetO)-controlled bicistronic transgene coding for a normal PDX1 protein and with a beta-galactosidase or EGFP reporter (see BCBC mouse M561). The combined modifications allow normal pancreatic development and function until doxycycline-administration renders the mouse conditionally null of the Pdx1 gene. This configuration for conditional expression of Pdx1is most effective when the transgene locus is homozygous. This allows embryonic developmental arrest at desired stages or cessation of function in adult mice by tetracycline administration. Person: Mark A. Magnuson, Jill Lindner, Jean-Philippe Cartailler STOCK Pdx1{tm1Macd}/J Vanderbilt University Medical Center