A Super Family of Putative Developmental Signaling Molecules Related to the Proto-Oncogene Wnt-1/int-1

Publisher Summary This chapter discusses the action of Wnt gene. The first member of this family ( Wnt gene) Wnt - 1 / int-1 was originally identified on the basis of its oncogenic action in mouse mammary tumor virus (MMTV) induced mammary tumors. In several strains of mice, pregnancy-dependent mammary tumors arise as a consequence of retroviral insertion, and subsequent enhancer-mediated activation, of a number of normal cellular genes. Collectively, these genes were named int genes to indicate their common mechanism of activation by MMTV integration. There is some common component to the pathway of Wnt gene action. Given the properties of the Wnt proteins, this is probably a cell surface receptor that normally functions in Wnt -mediated signaling in mammary tissue. Comparison of Wnt -1 protein sequences from mouse, human, Xenopus , zebra fish, and Drosophila reveals a number of strikingly conserved features. A hydrophobic stretch of amino acids with broad consensus to a signal peptide sequence is located at the amino terminus, suggesting that the protein is secreted. Wnt -1 action is confined to the developing central nervous system. In serial sections of embryos from 7.5–16.5 days of gestation, Wnt - 1 expression is only detected in neural tissue.