Functions as a transcriptional activator playing a crucial role during development. Functions in trophoblast differentiation and later in gastrulation, regulating both mesoderm delamination and endoderm specification. Plays a role in brain development being required for the specification and the proliferation of the intermediate progenitor cells and their progeny in the cerebral cortex. Also involved in the differentiation of CD8+ T-cells during immune response regulating the expression of lytic effector genes. Expressed in CD8+ T-cells. Detected at 7 weeks of development in the forebrain floorplate of the CNS. Expressed within the mantle layer and migrating neuroblasts of the telencephalon at 12.5 weeks of development. Up-regulated in CD8+ T-cells simultaneously stimulated with TGFB1 and IL4/interleukin-4. A translocation t(3;10)(p24;q23) located 215 kb 3' to the EOMES gene but leading to loss of its expression was identified in a large consanguineous family. Homozygous silencing produces microcephaly associated with corpus callosum agenesis, bilateral polymicrogyria, ventricular dilatation and a small cerebellum. Dubious isoform produced through aberrant splice sites.