Expression of the T-box gene Eomesodermin during early mouse development.

We report the expression pattern of a murine homolog of the Xenopus laevis T-box gene Eomesodermin. mEomes expression is first detected in the extra-embryonic ectoderm prior to gastrulation, and persists there until head-fold stages. In the embryo proper, mEomes is expressed throughout the early primitive streak, nascent mesoderm and in the anterior visceral endoderm. Although mEomes expression disappears from the embryo at late-streak stages, a second domain of mEomes expression is observed in the telencephalon beginning around E10.5.