Fig. 7. Extensive deletion analysis defines an essential 50 bp element A large number of deletion constructs were analyzed for expression in the embryo. M stands for the presence of the mutation at site 300, which leads to a dramatic increase in the sensitivity of the enhancers to DPP. Clearly, deletion of sequences between 444 (1/444m300) and 394 (1/394m300) (deletion of the 50 bp element) leads to a loss of expression in endodermal cells adjacent to ps 3 and ps 7. The equivalent deletion was also analyzed in the context of lab550.