Figure 1.

The Foxa2^loxP allele is efficiently and specifically deleted in pancreatic β cells by the Ins.Cre transgene. Immunofluourescence analysis of pancreas sections from mice at 16.5 d post coitum (a,b), postnatal day 8 (P8; c,d,g,h), and P22 (e,f), double-labeled for either Foxa2 (red) and insulin (green; a–f) or Foxa2 (red) and glucagon (green; g,h). Foxa2 is normally expressed in all islet cell types, including β cells and α cells, and in some acinar cells (a,c,e,g). (b) Foxa2 is inactivated in β cells as early as embryonic day 16.5 (E16.5) in Foxa2^loxP/loxP; Ins.Cre mice. Cre-mediated deletion of Foxa2 occurs in 85% of β cells in P8 mice (d) and in more than 99% of β cells in P22 mice (f). Arrows (b,d,f) show β cells that have Foxa2 deleted, whereas arrowheads (b,d) show β cells in which Foxa2 protein persists. However, Foxa2 is not deleted in either α cells (h) or acinar cells in Foxa2^loxP/loxP; Ins.Cre mice, indicating the specificity of the Ins.Cre transgene. Images were obtained at 400× magnification using fluorescent confocal microscopy of representative pancreatic sections from wild-type control (Control) mice (a,c,e,g) and mutant Foxa2^loxP/loxP; Ins.Cre mice (b,d,f,h).