Area identity shifts in the early cerebral cortex of Emx2-/- mutant mice

The specification of area identities in the cerebral cortex is a complex pr ocess, primed by intrinsic cortical cues and refined after the arrival of a fferent fibers from the thalamus. Little is known about the genetic control of the early steps of this process, but the distinctive expression pattern of the homeogene Emx2 in the developing cortex has prompted suggestions th at it is critical in this context. We tested this hypothesis using Emx2(-/- ) mice. We found that the normal spectrum of cortical areal identities was encoded in these mutants, but areas with caudal-medial identities were redu ced and those with anterior-lateral identities were relatively expanded in the cortex.