The previously identified RAP6 (Rab5 activating protein 6) was associated with plasma membrane mediated endocytosis and contains a Rab5 guanine nucleotide exchange factor (GEF) domain. RAP6 has been shown to act a Ras activating protein (GAP) domain. The identification of RAP6 and its crucial role in both receptors mediated endocytosis and fluid phase endocytosis presents the opportunity to investigate its role in murine embryonic development and in the adult brain. To confirm and characterize the presence of RAP6 during embryonic development and in the adult brain, the current study examined the expression of both the RGD and the Vps9 domains of RAP6 through in situ hybridization. We present an extensive evaluation of the expression for both RAP6 domains through in situ hybridization of 12.5 and 14.5 weeks old C67 mouse embryos and adult C67 mouse brain. The current study confirms the presence of both RAP6 domains and presents an extensive evaluation its expression in embryonic development and the adult brain. These data together support the role of RAP6 in receptor mediated endocytosis and fluid phase endocytosis relevant active during murine embryonic development and adult brain processes.