Skn-1a/Pou2f3 is required for the generation of Trpm5-expressing microvillous cells in the mouse main olfactory epithelium

Abstract

BackgroundThe main olfactory epithelium (MOE) in mammals is a specialized organ to detect odorous molecules in the external environment. The MOE consists of four types of cells: olfactory sensory neurons, supporting cells, basal cells, and microvillous cells. Among these, development and function of microvillous cells remain largely unknown. Recent studies have shown that a population of microvillous cells expresses the monovalent cation channel Trpm5 (transient receptor potential channel M5). To examine functional differentiation of Trpm5-expressing microvillous cells in the MOE, we investigated the expression and function of Skn-1a, a POU (Pit-Oct-Unc) transcription factor required for functional differentiation of Trpm5-expressing sweet, umami, and bitter taste bud cells in oropharyngeal epithelium and solitary chemosensory cells in nasal respiratory epithelium.ResultsSkn-1a is expressed in a subset of basal cells and apical non-neuronal cells in the MOE of embryonic and adult mice. Two-color in situ hybridization revealed that a small population of Skn-1a-expressing cells was co-labeled with Mash1/Ascl1 and that most Skn-1a-expressing cells coexpress Trpm5. To investigate whether Skn-1a has an irreplaceable role in the MOE, we analyzed Skn-1a-deficient mice. In the absence of Skn-1a, olfactory sensory neurons differentiate normally except for a limited defect in terminal differentiation in ectoturbinate 2 of some of MOEs examined. In contrast, the impact of Skn-1a deficiency on Trpm5-expressing microvillous cells is much more striking: Trpm5, villin, and choline acetyltransferase, cell markers previously shown to identify Trpm5-expressing microvillous cells, were no longer detectable in Skn-1a-deficient mice. In addition, quantitative analysis demonstrated that the density of superficial microvillous cells was significantly decreased in Skn-1a-deficient mice.ConclusionSkn-1a is expressed in a minority of Mash1-positive olfactory progenitor cells and a majority of Trpm5-expressing microvillous cells in the main olfactory epithelium. Loss-of-function mutation of Skn-1a resulted in complete loss of Trpm5-expressing microvillous cells, whereas most of olfactory sensory neurons differentiated normally. Thus, Skn-1a is a critical regulator for the generation of Trpm5-expressing microvillous cells in the main olfactory epithelium in mice.

Expression of homeobox genes in the mouse olfactory epithelium

“…3B). In the last group, the Pou2f3 homeobox gene showed no colocalization with Gap43 and Omp genes, but Pou2f3 + cells colocalized with the monovalent cation channel Trpm5 positive cells and basal cells (not shown) as reported by Yamaguchi et al ().…”

Deconstructing Olfactory Stem Cell Trajectories at Single-Cell Resolution

“…In support of this prediction, nine of ten clones containing microvillous cells also contain neurons (Figure 4E). Microvillous cells are rare in comparison to olfactory sensory neurons (Hansen and Finger, 2008; Jia et al, 2013; Ogura et al, 2011; Yamaguchi et al, 2014); this difference is reflected by the small number of microvillous cell-containing clones detected (12% of neuron-containing clones), as well as the low number of microvillous cells present in any given microvillous-containing clone (1.2 +/− 0.1; Figure 4H). These clonal lineage tracing results are complemented by a similar, non-clonal lineage tracing analysis using a knockin Ascl1-CreER driver (Kim et al, 2011), which recapitulates Ascl1’s expression in postnatal GBCs (Figure S4) (Manglapus et al, 2004).…”

Lack of TRPM5-Expressing Microvillous Cells in Mouse Main Olfactory Epithelium Leads to Impaired Odor-Evoked Responses and Olfactory-Guided Behavior in a Challenging Chemical Environment

“…The Skn-1a -/- line of mice (RRID:IMSR_RBRC05254) was originally generated by Matsumoto et al (2011). The lack of TRPM5-MCs in the MOE of these mice has been characterized previously (Yamaguchi et al, 2014). In standard housing conditions, mice were group-housed (two to five mice per cage) in an open-top cage system in our animal facility.…”