Differential reaction of outgrowing olfactory neurites monitored in explant culture

Abstract

Olfactory sensory neurons (OSNs) send their axons to distinct glomeruli in the olfactory bulb. On the way to their target, outgrowing axons are guided, fasciculated, and resorted before they extend in homotypic bundles to the glomerulus. The molecular mechanisms underlying these complex processes supposedly involve multiple intrinsic and extrinsic cues. Although the contribution of typical guidance molecules has been proposed, a detailed understanding of the olfactory wiring process remains elusive. By using in vitro cultures of the olfactory epithelium (OE) from gene-targeted mice, which allowed visualization of mature OSN and their axons, the impact of distinct molecular and cellular cues on defined OSN populations could be studied. The differentiating factor retinoic acid induced a heterogeneous response pattern of OMP expression and axon elongation. Cocultures with forebrain explants revealed that tissue from the presumptive olfactory bulb of embryonic stage E14 exhibited nonpermissive, repellent effects on outgrowing neurites, whereas precultured bulb tissue strongly attracted them, even from distantly located OE explants. A selective attraction of fibers from OSNs expressing defined odorant receptor types to distinct bulb explants was observed. These data indicate a differential reaction of OSNs to their target tissue.

Decreased demand for olfactory periglomerular cells impacts on neural precursor cell viability in the rostral migratory stream

“…1E,F). The mOR256-17-GFP olfactory sensory neurons traversed the cribriform plate and coalesced into glomeruli as previously described1727 but the number of olfactory sensory neurons was strongly reduced in MT1-MMP −/− compared to controls (inserts in Fig. 1E–G).…”

“…In order to investigate if MT1-MMP also impacts on the formation of osseous structures which allow neuronal trajectories to access the brain we traced distinct olfactory sensory neurons from the nasal cavity into the olfactory bulb using mOR256-17-GFP mice17 crossbred with MT1-MMP −/− or wild-type controls (n = 4; Fig. 1E,F).…”

“…Analyses of the projection pattern from olfactory sensory neurons expressing mOR256-17 were performed using our previously generated transgenic mouse strain which carries a targeted mutation of IRES-tauGFP at the mOR256-17 gene locus17. For tissue preparations, animals were anesthetised and sacrificed as approved by the local administrative authority.…”

OMP-ZsGreen fluorescent protein transgenic mice for visualisation of olfactory sensory neurons in vivo and in vitro

“…Therefore the use of these mice may not be suitable for many studies. The OMP-GFP mice have previously been used for explant assays to analyse olfactory axon growth and provided good resolution of axons using a single time point (Luxenhofer et al, 2008). However, we found that the GFP expression in living axons was weak and faded rapidly with repeated exposure and hence we were unable to obtain high magnification, high resolution images of OMP-GFP axons using timelapse microscopy.…”

Adiponectin Enhances the Responsiveness of the Olfactory System

“…For this study, adult wildtype C57BL/6J mice purchased from Charles River (Sulzfeld, Germany) and animals from our previously generated transgenic mouse line which carry a targeted mutation of IRES-tauGFP at the mOR256-17-locus [11] were used. All animals were kept at a 12h/12h light/dark cycle and had free access to water.…”