Figure 7.

Cells expressing endocrine functions appear in the spleen of p48-deficient mice. Immunohistochemistry was carried out on dissected intestinal tracts of 18-dpc −/− embryos (b–f) or from spleen of newborn −/− mice (g). (a) The abdominal region of an 18-dpc −/− embryo showing, in this particular case, that insulin-producing cells are absent from the intestinal mesentery. Individual cells expressing the endocrine markers indicated were detected exclusively in spleens of −/− mice from 18 dpc onward. They were not observed in spleens of +/− mice (h) or 16-dpc −/− embryos (i) as exemplified by the absence of glucagon staining. (Insets) Single intrasplenic cells positive for the respective endocrine markers at a higher magnification. (Inset in g) Cell simultaneously expressing insulin in its cytoplasm (red color) and Pdx-1 in the nucleus (dark blue stain). Note that individual immunopositive cells are also present in the mesentery adjacent to the spleen (e.g., in e).