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Integrating Organ Induction
During animal development, multiple signaling pathways specify the induction of organ progenitors such as those in the pancreas and liver. Wandzioch and Zaret (p. 1707) investigated how three signaling pathways converge on the earliest genes specifying these organs. Within hours, multiple changes were observed in the inductive network with different signals operating in parallel. The findings may help to explain the incomplete programming seen in various stem cell differentiation protocols.
Studies of the formation of pancreas and liver progenitors have focused on individual inductive signals and cellular responses. Here, we investigated how bone morphogenetic protein, transforming growth factor–β (TGFβ), and fibroblast growth factor signaling pathways converge on the earliest genes that elicit pancreas and liver induction in mouse embryos. The inductive network was found to be dynamic; it changed within hours. Different signals functioned in parallel to induce different early genes, and two permutations of signals induced liver progenitor domains, which revealed flexibility in cell programming. Also, the specification of pancreas and liver progenitors was restricted by the TGFβ pathway. These findings may enhance progenitor cell specification from stem cells for biomedical purposes and can help explain incomplete programming in stem cell differentiation protocols.
↵* Present address: Department of Cell and Developmental Biology, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA.