Fig. 3. Neonatal O/E2^lacZ/lacZ mice exhibit ORN projection defect. (A) Whole-mount X-gal staining of O/E2^lacZ/+ and O/E2^lacZ/lacZ neonates showing the ORN projection patterns to the OB. At P1 in O/E2^lacZ/+ animals, the ß-gal positive ORN axons cover most of the OB surface, but the O/E2^lacZ/lacZ mice lack projections to the lateral and dorsal regions of their OB. In addition to the projection phenotype, the OB of neonatal O/E2^lacZ/lacZ animals are significantly smaller and rounder in shape than those of the heterozygous littermates. Similar results were observed in additional O/E2^lacZ/lacZ mice (n=8). (B) ß-Galactosidase staining and OMP immunohistochemistry of coronal sections through the OB of O/E2^lacZ/+ and O/E2^lacZ/lacZ neonates showing the ORN projection patterns to the OB. The sections are matched by the morphology of the olfactory turbinates. In the sections of O/E2 heterozygous neonate, the ß-gal and OMP-positive ORN axons covers most of the OB surface, but the O/E2^lacZ/lacZ animals display no apparent projections to the lateral and dorsal regions of their OB. In addition, the sections also demonstrate the shortening of the OB in the O/E2^lacZ/lacZ animals. In all panels, dorsal is at the top and medial is towards the right.