Changes in embryonic cell fate produced by expression of an endodermal transcription factor, Xsox17

Many molecules induce the ectopic expression of tissue-specific genes in Xe nopus embryos. Conversely, interfering with their activity disrupts pattern s of gene expression, implicating them in normal development. Does this mea n that they control cell fate (i.e. position, as well as differentiation)? Xsox17 alpha and beta can induce ectopic expression of endodermal markers; inhibiting their function suppresses expression of endodermal marker genes in the developing gut (Cell 91 (1997) 397). Here we show the effect of thes e manipulations on cell lineage. Expressing Xsox17 in a cells normally fate d to become ectoderm causes their descendants either to relocate into the e mbryonic gut or to die at a late developmental stage. Conversely, disruptin g Xsox17 activity in cells normally fated to be endodermal causes them to e nter mesodermal and ectodermal lineages. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.