A recombinase-mediated cassette exchange-derived cyan fluorescent protein reporter allele for Pdx1

Fluorescent protein (FP) reporter alleles are useful both for identifying and purifying specific cell populations in the mouse. Here, we report the generation of mouse embryonic stem cells that contain a pancreatic and duodenal homeobox 1 (Pdx1) loxed cassette acceptor (Pdx1(LCA)) allele and the use of recombinase-mediated cassette exchange to derive mice that contain a Pdx1(CFP) (Cerulean) reporter allele. Mice with this allele exhibited cyan fluorescence within the previously well-characterized Pdx1 expression domain in posterior foregut endoderm. Immunolabeling showed that endogenous Pdx1 was coexpressed with CFP at all time points examined. Furthermore, fluorescence-activated cell sorting was used to isolate CFP-positive cells from E11.5 and E18.5 embryonic tissues using both 405 and 445 nm lasers, although the latter resulted in a nearly 50-fold increase in emission intensity. The Pdx1(CFP) allele will enable the isolation of specific foregut endoderm and pancreatic cell populations, both alone and in combination with other FP reporter alleles.