INDUCTION OF MESODERM IN XENOPUS-LAEVIS EMBRYOS BY TRANSLATION INITIATION-FACTOR 4E

The microinjection of messenger RNA encoding the eukaryotic translatio n initiation factor 4E (elF-4E) into early embryos of Xenopus laevis l eads to the induction of mesoderm in ectodermal explants. This inducti on occurs without a stimulation of overall protein synthesis and is bl ocked by the co-expression of a dominant negative mutant of the proto- oncogene ras or a truncated activin type II receptor. Although other t ranslation factors have been studied in vertebrate and invertebrate em bryos, none have been shown to play a direct role in development. The results here suggest a mechanism for relaying and amplifying signals f or mesoderm induction.