Oct4 is a stem cell expression marker, and persistence of its expression retains pluripotency in embryonic stem (ES) cells. Our results indicate a pattern of gradual decrease in Oct4 expression, which is prominent in the blastocyst and markedly reduced in the gastrula and neurula. The presence of POU transcription factor-like domain in Gas7 prompted us to look for its expression in the early embryonic cells. We have observed high expression of the Gas7 protein in blastocysts that gradually decreased in the neurula stages. The localization of Gas7 was initially seen throughout the blastocyst, but was later confined to dorsal ectodermal regions of the neurula, conforming with its role in neuronal differentiation. Our data reveal that Gas7 might play a role in cellular migration and cell protection in the ES cells of mouse embryo.