Fig. 5. Expression pattern of rat PBX1 in coronal sections of P14 rat brain. A–C,PBX1 expression is abundant in the subventricular zone as it follows the lateral ventricle throughout a significant caudal to rostral extent of the brain. D, E, At more rostral levels, where the subventricular zone becomes continuous with the subependymal zone of the olfactory bulb, PBX1 expression is maintained in this pathway. F, In the olfactory bulb, expression is detected in layers that are the primary destination of cells migrating from the subventricular zone: the granule cell layer, mitral cell layer, and glomerular layer. PBX1 expression is not detectable in the external plexiform layer. G, Same section as in F stained with cresyl violet shows olfactory bulb cell layers and relative cell densities. SVZ, Subventricular zone; lv, lateral ventricle; SEZ, subependymal zone; gcl, granule cell layer; ml, mitral cell layer; gl, glomerular layer; ip, internal plexiform layer; ep, external plexiform layer. Thearrows in A–D indicate the subventricular zone and the migratory pathway to the olfactory bulb. Scale bar, 1 mm.