EXPRESSION PATTERN OF THE MOUSE T-GENE AND ITS ROLE IN MESODERM FORMATION

FORMATION of mesoderm is a crucial event in vertebrate development, establishing many of the important features of the body1-4. Recent studies have implicated molecules that are similar to growth factors in mesoderm formation inXenopus5-7, but other gene products involved in this process have yet to be identified. Genetic evidence indicates that in the mouse the T gene (Brachyury) has a role in the formation and organization of mesoderm. Mice homozygous for mutant alleles of the T gene do not generate enough mesoderm8, and show severe disruption in morphogenesis of mesoderm-derived structures, in particular the notochord9-12. The cloning of the T gene13has now allowed us to examine its expression pattern. We report that T-geneexpression occurs in both early stage mesoderm and its epithelial progenitor, and then becomes restricted to the notochord. This expression pattern correlates with the tissues affected in the T-gene mutant, and indicates that the T gene has a direct role in the early events of mesoderm formation and in the morphogenesis of the notochord. © 1990 Nature Publishing Group.