Eomesodermin-At Dawn of Cell Fate Decisions During Early Embryogenesis

Proteins of the large family of T-box transcription factors are implicated in a broad spectrum of developmental processes. Loss-of-function mutations of T-box(Tbx) factors frequently cause severe embryonic phenotypes, often resulting from defects in cell fate specification and lineage differentiation. This review summarizes current knowledge on the functions of the T-box transcription factor Eomesodermin (Eomes) from postfertilization development until gastrulation stages of vertebrate embryos. Eomes exhibits evolutionary conserved functions in cell lineage specification and morphogenesis during gastrulation in all studied vertebrate model systems. In addition, during mammalian embryogenesis, Eomes is crucially required in extraembryonic tissues that are specific for intrauterine development. This chapter mainly focuses on mammalian development of mouse; however, common functions shared among other vertebrate model system, such as embryos of zebrafish and Xenopus laevis, will be compared in the context of specification cell lineages during gastrulation. Furthermore, this review recapitulates the current understanding of the molecular functions and transcriptional targets of Eomes as component of transcriptional complexes that guide cell-type specification and morphogenesis of early vertebrate embryos.