Conditional gene targeting in mouse pancreatic β-cells: Analysis of ectopic Cre transgene expression in the brain

  1. Peter J. Dempsey (petedemp{at}med.umich.edu)2,3
  1. 1Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, Chicago, IL 60637
  2. 2Division of Gastroenterology, Department of Pediatrics and Communicable Diseases
  3. 3Department of Molecular and Integrative Physiology
  4. 4Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine
  5. 5Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109
  6. 6Division of Diabetes, Endocrinology and Metabolism, Department of Medicine
  7. 7Department of Cell and Developmental Biology
  8. 8Center for Stem Cell Biology
  9. 9Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, 37232
  10. 10Departments of Medicine, Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210
  11. 11VA Tennessee Valley Healthcare System, Nashville, TN 37232

Abstract

Objective- Conditional gene targeting has been extensively used for in vivo analysis of gene function in β-cell biology. The objective of this study was to examine whether mouse transgenic Cre lines used to mediate β-cell- or pancreas-specific recombination also drive Cre expression in the brain.

Research design and methods - Transgenic Cre lines driven by Ins1, Ins2, and Pdx1 promoters were bred to R26R reporter strains. Cre activity was assessed by β-galactosidase (β-gal) or YFP expression in the pancreas and brain. Endogenous Pdx1 gene expression was monitored using Pdx1tm1Cvw lacZ knock-in mice. Cre expression in β-cells and co-localization of Cre activity with orexin-expressing and leptin-responsive neurons within the brain was assessed by immunohistochemistry.

Results- All transgenic Cre lines examined that used the Ins2 promoter to drive Cre expression showed widespread Cre activity in the brain whereas Cre lines that used Pdx1 promoter fragments showed more restricted Cre activity primarily within the hypothalamus. Immunohistochemical analysis of hypothalamus from Tg(Pdx1-cre)89.1Dam mice revealed Cre activity in neurons expressing orexin and in neurons activated by leptin. Tg(Ins1-Cre/ERT)1Lphi mice were the only line that lacked Cre activity in the brain.

Conclusions- Cre-mediated gene manipulation using transgenic lines that express Cre under the control of the Ins2 and Pdx1 promoters are likely to alter gene expression in nutrient-sensing neurons. Therefore, data arising from the use of these transgenic Cre lines must be interpreted carefully to assess whether the resultant phenotype is solely attributable to alterations in the islet β-cells.

Footnotes

    • Received April 30, 2010.
    • Accepted August 21, 2010.