The properties of transcriptional networks early in the differentiation of human pancreatic cells are inferred from the properties of well-studied networks in mouse models. In mice, the first visible sign of pancreatic development is the appearance of pancreatic buds at about embryonic day 9. The cells in these buds are already committed to differentiate into specialized cells of the exocrine and endocrine pancreas. Expression of transcription factors including Hnf1b, Hnf6, and Pdx1, as well as responsiveness to Fgf10 (fibroblast growth factor 10), up-regulates the expression of factors including Ptf1, Onecut3, Lrh1, and Nkx6.1 (Servitja and Ferrer 2004; Chakrabarti and Mirmira 2003).