ABSTRACT: Tooth and hair development starts from ectodermal invaginations. However, the determination of organ-specific cell fates is poorly understood. The transcription factor Sox21 is expressed in the epithelium of developing teeth. We discovered that disruption of Sox21 caused severe enamel hypoplasia and ectopic hair formation in the gingiva in Sox21 knockout incisors. We dissected tooth germ from P1 Sox21 KO and control incisors for microarray. In particular, several markers of ameloblast maturity, i.e. amelotin (Amtn), laminin α3 (Lama3), and kallikrein-related peptidase 4 (Klk4), were included among the downregulated molecules in Sox21 KO tooth germ, whereas the expression of Mmp20 and Amel was not changed. On the other hand, numerous keratin-related genes were upregulated in the Sox21 KO tooth germ and WT skin. As in the microarray results, the expression of dental epithelial stem cell marker Sox2, as well as keratin family and hair-related genes such as Lgr5, were increased in Sox21 KO dental epithelium. Taken together, these results reflected the perturbed differentiation of ameloblasts and a cell fate change in the Sox21 KO incisors.
Project description:Incisor enamel organ epithelial cells were isolated and enzymatically processed from postnatal day 4 mice transgenic for Amelx-promoter driven tdTomato. Single cell suspensions were subjected to fluorescence-activated cell sorting (FACS) to isolate tdTomato positive ameloblasts. tdTomato-positive cells were isolated from enamel organ epithelial from the incisors of three mouse lines, which were Mmp20+/+ -AT4 (WT), Mmp20-/--AT4 (KO), Mmp20+/+ Tg-AT4 (Tg, overexpress MMP20). We used Fukuoka Dental College mouse ameloblast PCR array panel to quantitate gene expression of genes associated with enamel formation, cell migration and cell adhesion from ameloblasts.
Project description:Throughout the various stages of tooth development, reciprocal epithelial-mesenchymal interactions are the driving force, for instance crucially involved in the differentiation of mature enamel-forming ameloblasts and dentin-producing odontoblasts. Here we established mouse tooth ‘assembloids’, comprised of tooth organoid-derived dental epithelial cells (from mouse molars and incisors) cultured together with molar dental pulp stem cells (DPSCs), to mimic these developmental interactions. Assembloids from both tooth types were grown both in basal- and differentiation-inducing conditions. Single cell transcriptomics analysis was applied to in detail characterize and validate the newly developed mouse tooth assembloid model and evaluate the induced differentiation processes.
Project description:Cell fate is defined by specific transcriptional program. Here, we provide evidence that the transcriptional coactivator, Mediator 1 (MED1), is critical in determining the cell fate of ectodermal epithelia. MED1 ablation disrupted enamel formation and generated hair adjacent to the incisors. Deletion of MED1 altered the differentiation of dental epithelia to one expressing epidermal and hair genes similar to the skin. The cellular switch from dental to epidermal/hair lineage was characterized by abnormalities in MED1 deficient dental epithelial stem cells residing in cervical loop. MED1 deficiency caused a failure of dental epithelial stem cells to commit to the dental stratum intermedium regulated by Notch signaling. Instead, MED1 deficient cells retained stem cell potentials expressing Sox2. These cells were eventually adopted an epidermal fate probably through calcium provided through capillary networks, which is originally utilized for enamel formation. Our results demonstrate that MED1 regulates Sox2/Notch1 regulated cell lineage determination in dental epithelia. Our study also shows a potential to regenerate hairs by using genetically engineered dental tissues or cells outside of the skin. n=3 WT and KO (each sample contain dissected dental tissues from 3 mice combined)
Project description:Cell fate is defined by specific transcriptional program. Here, we provide evidence that the transcriptional coactivator, Mediator 1 (MED1), is critical in determining the cell fate of ectodermal epithelia. MED1 ablation disrupted enamel formation and generated hair adjacent to the incisors. Deletion of MED1 altered the differentiation of dental epithelia to one expressing epidermal and hair genes similar to the skin. The cellular switch from dental to epidermal/hair lineage was characterized by abnormalities in MED1 deficient dental epithelial stem cells residing in cervical loop. MED1 deficiency caused a failure of dental epithelial stem cells to commit to the dental stratum intermedium regulated by Notch signaling. Instead, MED1 deficient cells retained stem cell potentials expressing Sox2. These cells were eventually adopted an epidermal fate probably through calcium provided through capillary networks, which is originally utilized for enamel formation. Our results demonstrate that MED1 regulates Sox2/Notch1 regulated cell lineage determination in dental epithelia. Our study also shows a potential to regenerate hairs by using genetically engineered dental tissues or cells outside of the skin. n=4 WT and KO (each group contains dissected dental tissues from 3 mice combined)
Project description:Cell fate is defined by specific transcriptional program. Here, we provide evidence that the transcriptional coactivator, Mediator 1 (MED1), is critical in determining the cell fate of ectodermal epithelia. MED1 ablation disrupted enamel formation and generated hair adjacent to the incisors. Deletion of MED1 altered the differentiation of dental epithelia to one expressing epidermal and hair genes similar to the skin. The cellular switch from dental to epidermal/hair lineage was characterized by abnormalities in MED1 deficient dental epithelial stem cells residing in cervical loop. MED1 deficiency caused a failure of dental epithelial stem cells to commit to the dental stratum intermedium regulated by Notch signaling. Instead, MED1 deficient cells retained stem cell potentials expressing Sox2. These cells were eventually adopted an epidermal fate probably through calcium provided through capillary networks, which is originally utilized for enamel formation. Our results demonstrate that MED1 regulates Sox2/Notch1 regulated cell lineage determination in dental epithelia. Our study also shows a potential to regenerate hairs by using genetically engineered dental tissues or cells outside of the skin. n=3 WT and KO (each sample contain dissected dental tissues from 3 mice combined)
Project description:Cell fates are defined by specific transcriptional program. We developed a mouse model, in which transcriptional program for ectoderm cell fate is altered in tooth and skin. Previously, we showed that genomic deletion of one subunit of Mediator complex, Mediator 1 (Med1) in vivo regenerate ectopic hair in incisors by disrupting Notch mediated enamel epithelial differentiation. However, precise process and molecular mechanism to induce epidermal fate are not clear. Med1 deficient dental epithelial stem cells exerts transcriptional program for skin epithelia reminiscent of the pattern in the skin. Epidermal transcripts were first induced prior to hair genes during dental epithelial differentiation, resemble to the pattern of embryonic developmental process of the skin. Hair genes was specifically induced at the anagen stage synchronized with hair cycling in the skin. Epidermal program was also induced in cultured adult stem cells called dental epithelial stem cell (DESC) that is derived from micro-dissected Med1 KO cervical loop tissues that are essential for continuous regeneration of mouse incisors. Gene expression profiles for the primary DESC with colony forming capability revealed that Med1 deletion suppressed Tgfb signaling by reducing the expression of ligands (Tgfb1, Inhibin ba), receptors and their extracellular targets such as Ctgf. Med1 deletion also induced Tgfb regulated reprogramming transcription factor, Klf4 that also known to drive transcription for epidermal genes. TGFb signaling was also suppressed in Med1 null epidermis in skin, in which epidermal fate was induced in hair follicle keratinocytes. Med1 silencing blocked expression of TGFb1 and suppressed both basal and recombinant TGFb induced Smad2/3 mediated transcription of TGFb target genes in vitro. These results demonstrate that Med1 deletion enhances epidermal transcriptional program in adult stem cells through regulation of TGFb signaling.
Project description:Purpose: the goals of this study are to explore the effect of loss of Ptip in Sp7 positive dental progenitor cells on CD45- Ter119- Tie2- dental progenitor cells Methods: CD45- Ter119- Tie2- dental progenitor cells were sorted by FACs in lower incisors from Ptipf/f and Ptipf/f;Sp7-cre mice and performed RNAseq Our finding reveals that Ptip as crucial regulator in tooth homeostasis, functioning to safeguard the Sp7+ progenitor cells epigenome from a breach in lineage confinement that triggers irreversible tooth defects. Conclusions: loss of Ptip unregulate dental development and active Wnt signal pathway
Project description:In this study, using mouse molar as the model, we developed a dual fluorescence reporter mouse to precisely track and analyze dental epithelium and mesenchyme at single-cell resolution from early embryonic to postnatal stages. Moreover, we constructed the virtual molar explorer (VMEx) to spatially map 15,967 molar-expressed genes and identified that Msx1+ Sdc1+ marked the developing dental papilla while surrounded by Msx1+ Sdc1- molar niche. Through tooth germ reconstitution and organoid culture in vitro and kidney capsule transplantation in vivo, we provided evidence that the Msx1+ Sdc1- dental follicle cells might function as the tooth organizers that promoted epithelium survival and tooth germ organization. Furthermore, the appearance of Msx1+ Sdc1+ dental papilla cells relied on the interaction between dental epithelium and Msx1+ Sdc1- dental follicle cells. Together, our results revealed the cellular dynamics of tooth development in mice and identified that the dental follicle might be the key driver of epithelial-mesenchymal interaction and tooth morphogenesis.
Project description:Single-cell transcriptomics has revolutionized tooth biology by uncovering previously unexplored areas. The mouse is a widely used model for studying human tissues and diseases, including dental pulp tissues. While human and mouse molars share many similarities, mouse incisors differ significantly from human teeth due to their continuous growth throughout their lifespan. The extent to which studies on mouse teeth can be applied to human disease translation remains underexplored. By leveraging multiple single-cell datasets, we constructed a comprehensive dental pulp cell landscape to clarify tissue similarities and species-specific differences between humans and mice. Notably, we identified a distinct cell population, Sfrp2hi fibroblast progenitors, found exclusively in mouse incisors and the developing tooth root of human molars. These cells are uniquely present to sustain continuous tissue growth. Mechanistically, we found that the transcription factor Twist1, regulated by MAPK phosphorylation, binds to the Sfrp2 promoter and modulates Wnt signaling activation to maintain stem cell identities. Our research reveals a previously unrecognized subset of dental mesenchymal stem cells instrumental in tooth growth. This distinct subset is evolutionarily conserved in both humans and mice, offering valuable translational insights.
Project description:Postnatal cell fate has been postulated to be primarily determined by the local tissue microenvironment. Here, we found that Mediator 1 (Med1) dependent epigenetic mechanisms dictate tissue-specific lineage commitment and progression of dental epithelia. Deletion of Med1, a key component of the Mediator complex linking enhancer activities to gene transcription, provokes a tissue extrinsic lineage shift, causing hair generation in the dental environment. Med1 deficiency gives rise to unusual hair growth via primitive cellular aggregates on incisors. Mechanistically, we found that Med1 establishes super-enhancers that control enamel lineage transcription factors in dental stem cells and their progenies. However, Med1 deficiency reshapes the enhancer landscapes and causes a switch from the dental epithelial transcriptional program towards hair and epidermis on incisors in vivo, and in dental epithelial stem cells in vitro. Med1 loss also provokes an increase in the number and size of enhancers. Interestingly, control dental epithelia already exhibit enhancers for hair and epidermal key transcription factors; these expand in size and transform into super-enhancers upon Med1 loss suggesting that these epigenetic mechanisms cause the transcriptomic and phenotypic shift towards epidermal and hair lineages. Thus, we propose a role for Med1 in safeguarding lineage specific enhancers, highlight the central role of enhancer accessibility and usage in lineage reprogramming and provide new insights into ectodermal regeneration. Duplicate Chip-seq for dental tisses from head region of cervical loop (CLH) containing dental epithelial stem cells and tail region (CLT) including progenies that were dissected from mandible of 4 week old conditional Krt14CreMed1 knockout (cKO) mice or littermate control (Ctrl) mice. Chip-seq was conducted by using antibodies against Mediator 1 (Med1) and H3K27ac (H3).