Figure 4

Muc1^IRES-CreERT2 is active in adult exocrine cells. (A-C) Recombination was induced in adult (P60) Muc1^IC2/+;Rosa26^EYFP/+ mice by administration of 10 mg tamoxifen, and mice were analyzed 2 days later by immunofluorescence for EYFP (green), amylase (B, red) and cytokeratin-19 (C, red), together with DAPI (blue) to mark nuclei. After a short term chase, Muc1^IC2 marks cells of the ductal network (closed arrowheads) as well as acinar cells (open arrowheads), suggesting that Muc1 is expressed in both duct and acinar cells. (D-E) Ductal Rosa26^EYFPlabeling by Muc1^IC2, shown in fields devoid of labeled acinar cells (D, magnified from panel C; E, independent field). As Rosa26^EYFPexpression is lower in duct cells than acini, we have increased the green signal in these panels to make ductal staining more obvious. (F) 8-month old TM-untreated control mouse, stained for EYFP (green), amylase (red) and cytokeratin-19 (white). Less than 0.1% of duct and acinar cells are labeled in the absence of TM. Scale bars: 100 μm. Abbreviations: ac, acinus; du, duct; is, islet.