Fig 1.
Schematic representation of TRPM5-positive MVCs and SCCs.
Previously known molecular markers and innervation pattern are represented. We report here the presence in MVCs of other SCC transduction signaling cascade elements: gustducin, PLCβ2, and T1R3 (underlined). Other than a few morphological differences and the fact that MVCs are not innervated by peptidergic trigeminal nerve fibers, SCCs and MVCs are the same cell type in two different locations of the nasal cavity.
Table 1.
Antisera used to characterize TRPM5-positive MV cells.
Fig 2.
Differential gene expression analysis of mouse OSNs and whole olfactory mucosa (WOM).
Fold-change was calculated as [OSNs]/[WOM], which gives positive results for those genes mainly expressed in the OSNs (green; Olfr, all olfactory receptors), while negative values can be associated to genes more abundant in non-neuronal cell types of the epithelium (blue and red). Underlined genes in red are the typically expressed by SCCs whose expression in MVCs was analyzed in this study.
Fig 3.
TRPM5-GFP-positive MVCs and validation of TRPM5 expression.
A. Schematic representation of a mouse nasal cavity and the location of the olfactory (OE) and respiratory (RE) epithelia. B. TRPM5-GFP-positive MVCs in the MOE are located only in the uppermost portion of the epithelium. C. TRPM5-GFP-positive SCCs in the RE span for the whole depth of the epithelium. CGRP immunoreactivity (red) shows the intimate relation of SCCs with the trigeminal nerve fibers. D-D′′. Colocalization of TRPM5 antibody with GFP in MOE of TrpM5-GFP mice. E-E′′. TrpM5-GFP mice missing a functional TrpM5 gene (TrpM5-GFP/TrpM5 knockout) were used to validate that the TRPM5 antibody labeling is absent in GFP-positive MVCs.
Fig 4.
TRPM5-positive MVCs are not OSNs.
A and B. OMP and PGP9.5, immunoreactive markers for OSNs, do not colocalize with GFP-positive MVCs in MOE from TrpM5-GFP mice. C and D. Immunoreactivity of CNG2A and ACIII, elements of the olfactory transduction signaling cascade, is not detected in TRPM5-GFP-positive MVCs.
Fig 5.
MVCs express markers of the cholinergic system.
A-A′′. Antisera against ChAT labels TRPM5-GFP-positive MVCs. B-B′′. The antisera against TRPM5 colocalizes with the ChAT-GFP-positive MVCs. C-C′′. VAChT immunoreactivity in TRPM5-GFP-positive MVCs.
Fig 6.
MVCs express elements of the taste transduction signaling cascade, similarly to SCCs.
A-A′′′. Double staining with gustducin and ChAT of MOE of TrpM5-GFP mice. GFP-positive MVCs co-label with gustducin (in blue, A′) and ChAT (in red, A′′).
Fig 7.
Plcb2-GFP mouse confirms the presence of PLCβ2 in MVCs, and Chat-GFP mouse validates the presence of elements of the cholinergic system in MVCs.
A-A′′. The antiserum against PLCβ2 labels the PLCβ2-GFP-positive MVCs, but there are no GFP-positive OSNs. B-B′′. TRPM5 immunoreactivity co-labels the PLCβ2-GFP-positive MVCs. C-C′′. ChAT antibody colocalizes with PLCβ2-GFP-positive MVCs. White arrows indicate immunoreactive MVCs.
Fig 8.
The taste receptor T1R3 is present in MVCs and possibly in OSNs as suggested by the RNA-seq data analysis.
A′-A′′′. GFP-positive MVCs and few OSNs are visible in the MOE of Tas1R3-GFP mice, but only T1R3-GFP-positive MVCs colocalize with gustducin.
Fig 9.
Peptidergic trigeminal nerve fibers rarely create a direct contact with MVCs.
A. CGRP-immunoreactive trigeminal fibers seem to never contact TRPM5-GFP-positive MVCs. B. Occasionally, SubP-immunoreactive trigeminal nerve fibers in spatial proximity of TRPM5-GFP-positive MVCs.