Function and origin of circumvallate taste bud cells from SOX10 expressing von Ebners glands

点击翻译按钮获取中文摘要

Project Summary/Abstract (abbreviations: TB - taste bud; CvP – circumvallate papilla; vEG – von Ebner's gland) In mammals, the sensory end organs for taste are taste buds (TBs) that reside primarily in the epithelium of taste papillae in the tongue -- fungiform, foliate, and circumvallate. In rodents the single circumvallate papilla (CvP) houses hundreds of TBs, which enables efficient analyses of TB cells and will be our focus in this proposal. TB cells are post-mitotic and they have a short lifespan and undergo continuous renewal, therefore, progenitors in the immediate surrounding tissue must be available to renew TB cells for homeostasis. Thorough information of TB cell function, origin, and differentiation is essential to understanding taste disorders caused by TB progenitor deficiencies. TB progenitor cells have been thought to reside in the basal layer of the stratified lingual epithelium and express Krt14, Krt5, p63, SOX2 and Lgr5. However, our recent published data have shown that certain TB cells (~35% of TB cells in the CvP) originate from a previously unappreciated source of progenitors under, but not within, the stratified tongue epithelium -- the SOX10-expressing (SOX10+) cells. The labeled TB cells were mainly type III that transduce a sour and a salt taste, and had a significantly lower level of pan-taste cell marker Krt8. Further studies on the tissue locations and lineage mapping of SOX10+ cells have led to the idea that von Ebner's gland (vEG) is the tissue nest of SOX10+ progenitors for TB cells in the CvP. This is supported by the report that TBs-containing “circular structures” formed where vEG ducts locate in transplanted CvP tissue. The goal of this application is to collect direct and solid evidence about whether SOX10+ ductal cells of vEGs migrate and differentiate to TB cells (Aim 1), and establish the transcriptomic profiles of CvP/vEG epithelial cells, including SOX10+ progenitors and their derived TB cells (Aim 2). In Aim 1, we will adopt the previously proven approaches for examining taste cell differentiation - the 3D cultures of dissociated cells and CvP/vEG transplantations. In addition to taking advantage of these in vitro and ex vivo systems, we will utilize genetically labeled (RFP+) SOX10+ ductal cells of vEGs and CvP/vEG complex from SOX10-iCreERT2/RFP mice to differentiate taste cells in 3D cultures and transplanted tissues. In Aim 2, we will take advantage of the power of a modern high-throughput technique, single cell (sc) RNA-Seq that enables a highly efficient and informative analysis, to establish the transcriptomic profiles of all types of CvP/vEG epithelial cells including SOX10+ progenitors in vEGs and derived TB cells. The yielded data will provide definitive information about the differentiation of SOX10+ vEG cells to TB cells and bring comprehensive information of gene expression for all CvP TB cells and surrounding epithelial cells including those TB progenitors such as SOX10+ vEG ductal cells. The data will be of significant value for a long term in facilitating studies for a clear understanding of TB cell functions and the mechanisms, tissue compartments and cell types of TB progenitors in CvP/vEGs. Key words: taste bud (TB); von Ebner's gland (vEG); circumvallate papilla (CvP); SOX10; progenitor.