Fig. 6. Altered expression of the goblet cell marker Muc2 in Klf4^–/– mice. (A,B) In situ hybridization for Muc2 in the colon at postnatal day 1. (A) Wild-type mice showed a goblet-cell specific expression pattern of Muc2 mRNA (arrows) with abundant expression adjacent to the apical mucigen granules. Staining was prominent only in surface epithelial cells. (B) Klf4^–/– mice had expression of Muc2 mRNA (arrows) in the epithelium, but this expression was not confined to cells with goblet morphology. Patchy expression was seen in cells throughout the epithelium.