Patent ID: 7413901

Claim:
A method of forming an explant that expresses insulin in vitro, comprising: (a) isolating a Spemann-Mangold organizer region from a vertebrate gastrula; (b) culturing said Spemann-Mangold organizer region for a predetermined period of time, wherein the period is determined by a comparison of pancreatic differentiation levels of said Spemann-Mangold organizer region which is cultured for different periods of time and treated with retinoic acid; (c) treating said Spemann-Mangold organizer region with retinoic acid of a predetermined concentration for a predetermined period of time, wherein the concentration is determined by a comparison of the pancreatic differentiation levels of said Spemann-Mangold organizer region which are treated with retinoic acid of different concentrations, and the period is determined by a comparison of pancreatic differentiation levels of said Spemann-Mangold organizer region which is treated with retinoic acid; and (d) culturing said Spemann-Mangold organizer region to produce an explant that expresses insulin.