Whole transcriptome profiling of taste bud cells

Abstract

Analysis of single-cell RNA-Seq data can provide insights into the specific functions of individual cell types that compose complex tissues. Here, we examined gene expression in two distinct subpopulations of mouse taste cells: Tas1r3-expressing type II cells and physiologically identified type III cells. Our RNA-Seq libraries met high quality control standards and accurately captured differential expression of marker genes for type II (e.g. the Tas1r genes, Plcb2, Trpm5) and type III (e.g. Pkd2l1, Ncam, Snap25) taste cells. Bioinformatics analysis showed that genes regulating responses to stimuli were up-regulated in type II cells, while pathways related to neuronal function were up-regulated in type III cells. We also identified highly expressed genes and pathways associated with chemotaxis and axon guidance, providing new insights into the mechanisms underlying integration of new taste cells into the taste bud. We validated our results by immunohistochemically confirming expression of selected genes encoding synaptic (Cplx2 and Pclo) and semaphorin signalling pathway (Crmp2, PlexinB1, Fes and Sema4a) components. The approach described here could provide a comprehensive map of gene expression for all taste cell subpopulations and will be particularly relevant for cell types in taste buds and other tissues that can be identified only by physiological methods.

Evolutionary signatures of photoreceptor transmutation in geckos reveal potential adaptation and convergence with snakes

“…; Sukumaran et al. ), gastrointestinal cells of mammals and teleost fish (Latorre et al. ; Mazzoni et al.…”

“…Alternatively, the lack of staining could be due to temporal, spatial, or developmental restrictions on expression. GNAT1 is also known to be expressed outside the eye in some vertebrates, including in the bitter taste receptors of mammals (He et al 2004;Sukumaran et al 2017), gastrointestinal cells of mammals and teleost fish Mazzoni et al 2013;Mazzoni et al 2015), and the pineal gland of zebrafish (Lagman et al 2015), and so might be present in these tissues in geckos as well. These alternative functions could account for the conserved selective constraint of the gene and its maintenance within gecko genomes.…”

A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli

“…While we previously reported that PLCβ3 is expressed in a subset of taste cells that are not Type II cells (Hacker et al, 2008), we have now demonstrated PLCβ3 is present in a subset of Type III cells. This idea is supported by recent RNA-sequencing analysis of individual Type II and Type III cells (Sukumaran et al, 2017) which identifies PLCβ3 expression in 30% of Type III cells. We searched this RNA-seq dataset of Type III cells (Sukumaran et al, 2017) to determine if other signaling components associated with PLCβ signaling are expressed in Type III taste cells.…”

“…This idea is supported by recent RNA-sequencing analysis of individual Type II and Type III cells (Sukumaran et al, 2017) which identifies PLCβ3 expression in 30% of Type III cells. We searched this RNA-seq dataset of Type III cells (Sukumaran et al, 2017) to determine if other signaling components associated with PLCβ signaling are expressed in Type III taste cells. We found that the alpha G-protein Gαq which activates PLCβ is expressed in these cells.…”

“…Type III cells are the only known population of taste cells that express VGCCs (Medler, Margolskee et al, 2003) and are functionally identified in live cell imaging by the ability to respond to cell depolarization with a Ca 2+ influx through the opening of VGCCs (Clapp et al, 2006, DeFazio, Dvoryanchikov et al, 2006, Lewandowski et al, 2016, Medler et al, 2003, Richter, Caicedo et al, 2003, Sukumaran, Lewandowski et al, 2017). Therefore, if a taste cell responded to 50mM KCl with a Ca 2+ signal, we concluded that it expresses VGCCs and is a Type III cell.…”