Emx and Otx gene expression in the developing mouse brain.

The homeobox genes Emx1, Emx2, Otx1 and Otx2 are all expressed in the rostral brain of embryos at E10. Their expression domains are continuous regions of the developing brain contained within each other, such that the expression domain of Otx2 contains that of the other three genes, the expression domain of Otx1 contains that of Emx1 and Emx2, and the expression domain of Emx2 contains that of Emx1. The Emx1 expression domain includes the dorsal telencephalon and it has a posterior boundary slightly anterior to that between the presumptive diencephalon and telencephalon, whereas the Otx2 expression domain covers almost the entire forebrain and midbrain. Starting from E10.75, Otx2 expression disappears progressively from the presumptive cerebral cortex, whereas Emx1, Emx2 and Otx1 are expressed in this structure until late gestation. In particular, Emx2 appears to be expressed exclusively in the germinal ventricular zone of the developing cerebral cortex.