Expression pattern of the mouse T gene and its role in mesoderm formation

Abstract

FORMATION of mesoderm is a crucial event in vertebrate development, establishing many of the important features of the body^1–4. Recent studies have implicated molecules that are similar to growth factors in mesoderm formation inXenopus^5–7, 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 notochord^9–12. 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.