Fig. 6

Altered convergence of P2-expressing sensory axons in the olfactory bulb (OB), in the absence of phosphatidylethanolamine binding protein-1 (PEBP1). Schematic diagram of the convergence of olfactory sensory neurons (indicated by drop shapes of different colors) expressing P2 (purple) and M72 (light blue) odorant receptors to form glomeruli (purple and light blue filled circles, respectively) in the OB in control (top) and PEBP1 KO (bottom) mice. Top, in controls, P2-OR and M72-OR expressing axons converge to form homogeneous glomeruli (homo P2 and homo M72) in specific loci of the OB. In PEBP1 KO mice (bottom), the location of the main homogeneous P2 glomerulus (P2 homo, purple filled circle) is shifted (red arrow) along the antero-posterior axis, in respect to controls (original location is indicated by an empty dashed circle). Furthermore, in PEBP1 KO mice, P2 axons target additional glomeruli, which are formed by fibers expressing different odorant receptors (i.e., heterogeneous glomeruli (P2 hetero), indicated by filled circle with two colors, purple and pink). The convergence of M72 expressing axons is similar in controls (top) and mutant mice (bottom). These results indicate that PEBP1 acts as a putative ligand for P2-axonal receptors and not for M72-axonal receptors. In the schematic sections of the olfactory bulb, shaded yellow backgrounds indicate the general antero-posterior gradient of PEBP1. MOE = main olfactory epithelium