Figure 5.

The pancreas of ngn3 mutants lacks endocrine precursors. An RNA probe recognizing both wild-type (a) and mutant (a′) ngn3 transcripts in the neural tube labels endocrine precursors in wild-type pancreas at E10.5 (b) but no cells in ngn3 mutant pancreas at the same stage (b′). Prox1 (29) transcripts mark the pancreatic epithelium in adjacent sections of the same embryos (c and c′). The absence of ngn3+ cells in mutant pancreas is unlikely to be due to their death, because no increase in apoptosis was detected in E10.5 mutant (d′) versus wild-type (d) pancreas. (d and d′) Gut cells undergoing apoptosis in the same sections shown in e and e′ are used as control for the TUNEL reaction. sc, spinal cord.