Ghrelin+ ε-cells are expanded and expression of prohormone convertase 2 is reduced in paired domain mutant embryos. A. Immunstaining of pancreatic sections of e18.5 wt and Pax6Aey18 mutant embryos. An increased number of ghrelin-expressing cells is seen in the paired domain mutants. These cells show variable degrees of Pax6 expression similar to the ε-cells in wt pancreas. B. ε-cells are expanded ~5fold in mutant animals. All ghrelin+ cells were quantified regardless of their glucagon expression. Glucagon/ghrelin double-positive cells were present in wt animals but absent in Pax6Aey18 homozygotes (data not shown). Thus the ghrelin+ cells in the mutants can be classified as ε-cells. C. rtPCRs from total pancreatic RNA of e18.5 wt and Pax6Aey18 mutant embryos. As expected, proglucagon expression is markedly reduced in the mutants. Of the other α-cell marker genes tested, only prohormone convertase 2 (PC2) shows a reduced expression level while the expression of Arx is increased.