Figure 4.

IA1 is specifically expressed in the islet lineage, immediately downstream of the proendocrine gene Ngn3. (A–J) In situ hybridization with probes specific for IA1 and Ngn3 on consecutive cryosections of embryonic pancreas from mutant mice deficient for the Ngn3, NeuroD1, Pax4, Arx or Pax6 transcription factors, respectively. (A, B) No IA1 transcripts are detected in the pancreas of Ngn3-deficient mice. Expression of IA1 and Ngn3 is unaffected in the pancreas of NeuroD1 (C, D), Pax4 (E,F), Arx (G, H) and Pax6 (I, J) null mutant embryos. Signals for IA1 and Ngn3 overlap on consecutive sections of pancreas from the different mutant mice. Magnification A–J: × 40.