Developmental plasticity of epithelial stem cells in tooth and taste bud renewal

In Cichlids, replacement teeth (RT) share a continuous band of epithelium with adjacent taste buds (TB) and both organs co-express stem cell factors in subsets of label-retaining cells. In the mouse and other mammals, the tongue inter molar eminence (IE) oral papillae of Follistatin (Fat, BMP antagonist) mutants exhibited dysmorphic invagination. By using NGS-derived transcriptome profiling (RNAseq) analysis, we compared differential gene expression in the mouse tongue tissue in Follistatin (Fst) mutants mice with the wild type controls. Our results demonstrated ectopic expression of dental markers in tongue IE indicating that vertebrate oral epithelium retains inherent plasticity to form tooth and taste-like cell types mediated by BMP, therefore revealed under appreciated epithelial cell populations with promising potential in bioengineering and dental therapeutics. Total RNA was extracted from mouse IE tissue at E17.5 in triplicate from Follistatin mutants and wild type mice. The mRNA profiles were generated by deep sequencing using Illumina Hiseq platform and the sequence reads that passed the quality filters were aligned with mouse mm10 reference genome by Partek workflows with default parameters. Aligned reads were annotated and normalized and differential gene expression was identify by GSA. Data analysis with BWA workflows revealed a number of potential differential tooth genes related to BMP signaling pathway that ectopically expressed in the tongue IE suggesting an evolutionary and developmental lineages of cells that function in oral organ systems may provide clues to their manipulation in regenerative medicine.

在慈鲷（Cichlids）中，替换齿（replacement teeth, RT）与邻近的味蕾（taste buds, TB）共享一片连续的上皮带，且两种器官在标记滞留细胞的亚群中共表达干细胞因子。在小鼠及其他哺乳动物中，卵泡抑素（Follistatin, Fst，骨形态发生蛋白BMP拮抗剂）突变体的舌磨牙间隆起（inter molar eminence, IE）处的口腔乳头呈现形态异常的内陷。本研究借助下一代测序（next-generation sequencing, NGS）衍生的转录组测序（RNA-seq）分析技术，对比了卵泡抑素突变型小鼠与野生型对照小鼠舌组织的差异基因表达情况。研究结果表明，舌磨牙间隆起区域出现了牙齿标志物的异位表达，提示脊椎动物口腔上皮保留了形成牙齿与味觉样细胞类型的固有可塑性，该过程由骨形态发生蛋白（BMP）介导；由此揭示了此前未被充分认知的上皮细胞群，其在生物工程与牙科治疗领域具备可观的应用潜力。研究人员从E17.5阶段的小鼠磨牙间隆起组织中提取总RNA，每组设置三次生物学重复，样本分别来自卵泡抑素突变小鼠与野生型小鼠。采用Illumina Hiseq平台开展深度测序以生成mRNA表达谱，通过质量过滤的序列读段通过Partek标准化分析流程（默认参数）与小鼠mm10参考基因组进行比对。比对得到的读段经注释与标准化处理后，通过基因集分析（Gene Set Analysis, GSA）鉴定差异基因表达。经BWA分析流程开展的数据挖掘显示，多个与骨形态发生蛋白信号通路相关的潜在牙齿差异基因在舌磨牙间隆起区域异位表达，这表明口腔器官系统中发挥功能的细胞，其演化与发育谱系或可为再生医学中的细胞操控提供关键思路。