Conditional gene targeting in mouse pancreatic ß-Cells: analysis of ectopic Cre transgene expression in the brain.
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.


METHODS
Transgenic Cre lines driven by Ins1, Ins2, and Pdx1 promoters were bred to R26R reporter strains. Cre activity was assessed by β-galactosidase or yellow fluorescent protein expression in the pancreas and the brain. Endogenous Pdx1 gene expression was monitored using Pdx1(tm1Cvw) 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 the 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.
Wicksteed
Barton
B
Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, Chicago, llinois, USA. wicksteed@uchicago.edu
Brissova
Marcela
M
Yan
Wenbo
W
Opland
Darren M
DM
Plank
Jennifer L
JL
Reinert
Rachel B
RB
Dickson
Lorna M
LM
Tamarina
Natalia A
NA
Philipson
Louis H
LH
Shostak
Alena
A
Bernal-Mizrachi
Ernesto
E
Elghazi
Lynda
L
Roe
Michael W
MW
Labosky
Patricia A
PA
Myers
Martin G
MG
Gannon
Maureen
M
Powers
Alvin C
AC
Dempsey
Peter J
PJ
D000818:Animals; D001921:Brain / Q000502:physiology; D003433:Crosses, Genetic; D004965:Estrogen Antagonists / Q000494:pharmacology; D005260:Female; D005697:Galactosides / Q000378:metabolism; D018390:Gene Targeting / Q000379:methods*; D017930:Genes, Reporter / Q000235:genetics; D007074:Immunoglobulin G; D007150:Immunohistochemistry; D007328:Insulin / Q000276:immunology; D050417:Insulin-Secreting Cells / Q000502:physiology*; D019426:Integrases / Q000235:genetics*; D020738:Leptin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D013629:Tamoxifen / Q000494:pharmacology*
D004965:Estrogen Antagonists; D005697:Galactosides; D007074:Immunoglobulin G; D007328:Insulin; D020738:Leptin; D013629:Tamoxifen; C045073:Cre recombinase; D019426:Integrases
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