Fig. 8. ast adults exhibit a disorganized glomerular map of the OB. The projection pattern of a subpopulation of OSNs was visualized by the OMP promoter-directed YFP expression in omp:yfp/+ and ast/ast;omp:yfp/+ adults. (A,C) Whole-mount lateral views of OBs under a fluorescence stereomicroscope. Note that the posterolaterally located glomeruli observed in wild type (arrowheads in A) are not present in ast mutants (C), whereas ectopic glomerulus-like structures are seen in the posteroventral portion of the OB in ast mutants (arrows in C). (B,D) Double immunostaining with antibodies against YFP (green) and SV2 (magenta) of sagittal sections through the entrance point of the olfactory nerve at the anterior tip of OB. YFP-labeled axons ectopically innervate anteroventral and posteroventral glomeruli in ast mutants (arrows in D). In addition, aberrant axonal fascicles penetrate through the cellular layer of the OB (arrowheads in D). (E) Whole-mount lateral view of the left telencephalic hemisphere in an ast adult. A single fluorescent fascicle passes through the posteroventral surface of the OB and penetrates into the ventral telencephalic area (arrowheads). (F) Higher magnification view of the misprojecting fascicle shown in E. ob, olfactory bulb; R, right; L, left; D-tel, dorsal telencephalon; V-tel, ventral telencephalon; a, anterior; d, dorsal. Scale bar: in C, 250 µm for A,C; in D, 100 µm for B,D; in E, 250 µm; in F, 100 µm.