OMP Gene Deletion Results in an Alteration in Odorant-Induced Mucosal Activity Patterns

Abstract

. Previous behavioral work, using a complex five-odorant identification task, demonstrated that olfactory marker protein (OMP) is critically involved in odor processing to the extent that its loss results in an alteration in odorant quality perception. Exactly how the lack of OMP exerts its influence on the perception of odorant quality is unknown. However, there is considerable neurophysiological evidence that different odorants produce different spatiotemporal patterns of neural activity at the level of the mucosa and that these patterns predict the psychophysically determined perceptual relationship among odorants. In this respect, OMP gene deletion is known to result in a constellation of physiologic defects (i.e., marked reduction in the electroolfactogram (EOG) and altered response and recovery kinetics) that would be expected to alter the odorant-induced spatiotemporal activity patterns that are characteristic of different odorants. This, in turn, would be expected to alter the spatiotemporal patterning of information that results from the mucosal projection onto the bulb, thereby changing odorant quality perception. To test the hypothesis that odorant-induced mucosal activity patterns are altered in mice lacking the gene for OMP, we optically recorded the fluorescent changes in response to odorant stimulation from both the septum and turbinates of both OMP-null and control mice using a voltage-sensitive dye (di-4-ANEPPS Molecular Probes, Eugene, OR) and a Dalsa 120 ϫ 120, 12-bit CCD camera. To maintain continuity with the previous behavioral work, the odorants 2-propanol, citral, carvone, ethylacetoacetate, and propyl acetate were again used. Each odorant was randomly presented to each mucosal surface in a Latin-Square design. The results of this study demonstrated that, for both mouse strains, there do indeed exist different spatiotemporal activity patterns for different odorants. More importantly, however, these patterns significantly differed between OMP-null and control mice. That is, although the general regions of characteristic activity for different odorants were the same in both mouse strains, the patterns in the null animals were degraded relative to controls. These data suggest therefore that the alterations in mucosal activity may serve as the substrate for the behaviorally observed changes in odorant quality perception in the null mutant.

Dysregulation of Gene Expression in a Lysosomal Storage Disease Varies between Brain Regions Implicating Unexpected Mechanisms of Neuropathology

“…For the changes that were found in only one region, the OB had the most (239) followed by the BS (154), CB (96), CT (50), HP (33) and ST (33). Examples are the 11-fold down-regulation in the OB of olfactory marker protein (Omp), expressed specifically in olfactory neurons, which when inactivated alters odorant perception [14], [28]; and the 8-fold down-regulation in the HP of Otx2 which controls neuron subtype identity, the fate of GABAergic neurons, and forebrain development [29], [30], [31]. There were 41 genes that were changed in five of the six regions (unchanged in only one), with the CB having 4 times as many of the unchanged genes as the next closest region (BS).…”

Odorants with multiple oxygen‐containing functional groups and other odorants with high water solubility preferentially activate posterior olfactory bulb glomeruli

“…Indeed, the watersoluble odorants ethyl acetoacetate, 1-propanol, and propyl acetate preferentially activated sensory neurons located in the anterior and dorsal parts of both the nasal septum and the nasal turbinates in experiments where voltage-sensitive dye responses were imaged in ex vivo preparations during artificially simulated nasal air flow (Youngentob et al, , 2003Kent et al, 1996). The central channel of the epithelium, however, projects exclusively to the dorsal aspect of the olfactory bulb and not to the posterior, midlateral, and midmedial regions that were activated by such odorants in the present study (Mori et al, 1985;Schwob and Gottlieb, 1986;Tsuboi et al, 2006).…”

The Lim homeobox geneLhx2is required for olfactory sensory neuron identity

“…3D). We next analyzed for the expression of Omp, which is a hallmark of mature OSN (Youngentob et al, 2003). Studies of neuronal differentiation in the OE show that ORs are expressed prior to onset of Omp expression (Iwema and Schwob, 2003).…”