Wnt signaling in gut organogenesis

Wnt signaling regulates some aspect of development of nearly all endoderm-derived organs and Wnts mediate both differentiation and proliferation at different steps during visceral organogenesis. Wnt2b induces liver formation in zebrafish ¹ and may combine with other inducers, Fibroblast Growth Factors 1 & 4 and Bone Morphogenetic Protein 4, to specify the mammalian liver.^2-5 Later in development, Wnts are critical for liver expansion and, finally, for terminal hepatocyte differentiation,^6-12 as reviewed elsewhere in this issue (Monga). Likewise, in the pancreas, Wnts drive proliferation of exocrine and endocrine cells^13,14 and promote acinar cell differentiation,^13,15 as reviewed in the chapter by Murtaugh. Here we examine the intricate involvement of Wnt signaling in growth and differentiation of the digestive tract.