Figure 5. Nkx6.1 and Pdx1 collectively stabilize beta cell identity.

(A–H) Immunofluorescence staining of pancreata from wild type, Nkx6.1^f/+;Ngn3-Cre, Pdx1^+/−, and Nkx6.1^f/+;Ngn3-Cre;Pdx1^+/− mice at postnatal day (P) 2 reveals occasional coexpression of insulin with glucagon but not with somatostatin in all genotypes (A–D; arrowheads and insets). Both Arx⁺ (E–H) and Arx⁻ (E′–H′) insulin⁺glucagon⁺ cells (arrowheads and insets) are found in all genotypes. (I) Quantification of the percentage of insulin⁺ cells co-expressing glucagon at P2 reveals significantly more insulin⁺glucagon⁺ cells in Nkx6.1^f/+;Ngn3-Cre;Pdx1 ^+/−, Nkx6.1^f/+;Ngn3-Cre, and Pdx1^+/− mice compared to wild type controls. In addition, Nkx6.1^f/+;Ngn3-Cre;Pdx1 ^+/− mice show more insulin⁺glucagon⁺ cells than either single heterozygous mutant (n = 3). (J) Quantification of insulin⁺ and glucagon⁺ cell numbers in P2 pancreata shows an increase in glucagon⁺ cells in Nkx6.1^f/+;Ngn3-Cre;Pdx1^+/− and Pdx1^+/− mice compared to Nkx6.1^f/+;Ngn3-Cre and wild type mice demonstrating that loss of a single Nkx6.1 allele does not significantly affect alpha cell numbers (n = 3). Ins, insulin; Glc, glucagon; Som, somatostatin. Scale bar = 50 µm. Error bars represent S.E.M; **p<0.01, N.S. = not significant.