To explore this issue we examined if homologous corridor-like cells exist in several mammalian (sheep, human) and reptile/bird species

(Chinese soft-shelled turtle, Nagashima et al., 2009; corn-snake, Gomez et al., 2008; and chicken) because it was described that corridor-like cells are not present in amphibians (Moreno and González, 2007 and Moreno et al., 2008). We first defined a molecular fingerprint of mouse corridor cells: they form a continuum expanding from the striatum into the Nkx2.1-positive MGE, and they express Islet1 but express neither Nkx2.1 (Lopez-Bendito et al., 2006) nor Foxp2 (Figure 2A; data not shown). Using this molecular fingerprint, we showed that corridor-like cells are present in all the species we examined (Figure 2; data not shown). Dinaciclib However, the shape of Panobinostat supplier the corridor varied: in mammalian species the corridor expands “around” the GP (Figures 2A–2D), whereas it shows an expansion directed toward the midline in reptile/bird embryos (Figures 2E–2H). Taken together, our data show that, like most telencephalic tangential streams of cell migration (Cobos et al., 2001, Metin et al., 2007 and Tuorto et al., 2003), corridor-like

cells are evolutionary conserved in reptiles/birds. The observation that corridor-like cells exist in species with external TAs raised the possibility that the guidance properties of these cells may have been acquired in mammals. To examine the cellular properties of nonmammalian Bay 11-7085 corridor cells, we took advantage of the chicken embryo, which provides a model accessible to experimental manipulations. Because mouse corridor cells are LGE-derived neurons migrating tangentially into the MGE that express Islet1, Ebf1, Meis2, and Nrg1 ( Lopez-Bendito et al., 2006), we used these characteristics to examine chicken corridor-like cells. By performing DiI labeling in slice cultures and expression studies, we showed that corridor-like cells migrate tangentially from the LGE (n = 13/18) and express cEbf1, cMeis2, and cNrg1, thereby

indicating that they share cellular and molecular properties with their mouse homologs (see Figure S1 available online; data not shown). Although chicken corridor-like cells do not guide TAs in vivo, they express cNrg1 (data not shown), suggesting the intriguing possibility that they might nevertheless exhibit permissive properties for TA growth. The guidepost activity of corridor cells in mice relies on the fact that these cells are permissive for TA growth and that TAs can respond to corridor-derived permissive cues. To test whether these properties are conserved in birds, we first grafted chicken dorsal thalamus explants into wild-type mouse embryonic brain slices in contact with the corridor ( Figures 3A and 3B). Remarkably, we observed that chicken TAs grow in the mouse ventral telencephalon (n = 6/11; Figures 3A and 3B).