Activation of the Wnt/β-catenin Signaling Reporter in Developing Mouse Olfactory Nerve Layer Marks a Specialized Subgroup of Olfactory Ensheathing Cells

Wnt reporter TOPgal mice carry a beta-galactosidase (beta gal) gene under the control of the Wnt/beta-catenin signaling responsive elements. We found that the intensely immunolabeled beta gal(+) cells were coimmunolabeled with Nestin and formed a tangentially oriented single-cell layer in the connecting or docking zone where the olfactory sensory axons attached to the brain surface during mid-gestation. During early postnatal development, beta gal(+) cells were located in the inner olfactory nerve layer (ONLi) and co-labeled with olfactory ensheathing cell (OEQ markers S100 beta and NPY but not with lineage-specific markers for neurons, oligodendrocytes, astrocytes, and microglia, demonstrating that the TOPgal marked a subpopulation of OECs. By confocal microscopy, we found that TOPgal activated processes extended along the developing glomerulus and formed multiple tunnel-like structures that ensheathe and bridge olfactory sensory axonal bundles from ONLi to the glomerulus, which may play a key role in glomerulus formation and convergent sorting of the peripheral olfactory axons. Developmental Dynamics 237-3157-3168, 2008. (C) 2008 Wiley-Liss, Inc.