Project description:The keratins are the typical intermediate filament proteins of epithelia, presenting with highly specific expression patterns related to the epithelial type and stage of cellular differentiation. They are important for the cytoplasmic stability and integrity of epithelia, and also involved in various intracellular signaling pathways. Several keratins have been proved to be associated with enamel formation. However, there is still lack of information on the expression patterns of keratins during tooth morphogenesis. In the present study, we analyzed the spatiotemporal expression of the keratin family members using cap analysis gene expression and single-cell RNA-sequence analysis, revealing that Krt15 and Krt17 were not only highly expressed during tooth development, but also specifically expressed in non-ameloblasts. Immunostaining of both embryotic and postnatal mouse tooth germs showed that keratin 15 was mostly expressed in outer enamel epithelium, whereas keratin 17 was mainly found in stratum intermedium. Microarray analysis discovered that a core set of proliferation related genes were upregulated in Krt15-knockdown dental epithelial cells. The results of both CCK8 assay and EdU staining indicated that the loss of keratin 15 resulted in a higher cell proliferation activity. Our findings suggested that Krt15 could be a marker gene of outer enamel epithelium, and might take a part in regulating cell proliferation of dental epithelial cells.
Project description:The tooth is a convenient experimental model for the study of the basic mechanisms of organ development, including differentiation, cellular interaction, morphogenesis, and production and mineralization of extracellular matrices. The rodent incisor teeth grow continuously and exhibit all stages of tooth development at any time. This characteristic makes them convenient models for the study of enamel formation, which occurs in several distinct stages along the tooth axis. The distribution and structure of mouse incisor enamel resemble that of the rat. The enamel covers only the labial aspect of the tooth, and can be divided into four layers: a thin inner prism-free layer, inner enamel with prism decussation, i.e. transverse rows of prisms with prisms inclined medially and laterally in alternate rows, outer enamel with parallel prisms inclined incisally and a thin superficial prism-free layer. Recently, we have described how this elaborate organization of the enamel is established in the initial enamel formed on the unerupted and unworn incisal tip of the incisors. The very first enamel formed, i.e. the most incisally situated enamel, is always prism-free, corresponding to the superficial layer in fully established enamel, although thicker. Going in apical direction, i.e. in the direction of initiation of new enamel formation, isolated prisms appear among the crystals continuous with the prism-free zone crystals. These initial prisms are in general inclined incisally, corresponding to the prisms in the outer enamel layer in the fully established enamel. Inner enamel with the characteristic decussation pattern is added somewhat further apically and increases in thickness with increasing enamel thickness. Based on the structure of the enamel that they produce, the ameloblasts producing the initial, thin, prism-free enamel at the incisal tip of the unworn mouse incisor are probably differently configured (e.g. lacking Tomes' processes), probably differently organized (e.g. not organized in transverse rows moving sideways in opposite directions), and probably have a shorter life-span than the more apically situated ameloblasts which produce thicker enamel with the full four-layered configuration of mouse incisor enamel. For this reason it would be of interest to compare the gene expression profile of the incisal tip segment where prism-free enamel is being formed with the profile of the immediately adjacent segment where enamel with all four layers is being formed. As long as the incisor is unworn enamel formation and gene expression in these segments will likely reflect mechanistic differences between these segments as regards enamel biosynthesis. MicroRNAs (miRNA) are a class of non-coding RNAs that regulate gene expression at a post-transcriptional level, and are considered as important regulatory molecules during foetal development. By binding to target mRNA, miRNA induce mRNA decay or translation repression. Recent bioinformatic predictions of miRNA targets in vertebrates indicate that hundreds of miRNAs are responsible for regulating the expression of up to 30% of the human protein-coding genes, and miRNAs have recently also been shown to regulate expression of hundreds of mRNAs in cultured cells. Recently, miRNA expression profiles of the developing murine molar tooth germ and submandibular salivary gland have been established. We here report expression profiling of miRNAs present in the two adjacent segments of the incisor tooth germ on which we also have carried out mRNA expression profiling. The results suggest that also miRNAs are abundantly, and differentially, expressed during development of the incisor tooth germ in mouse. By analogy with the mRNA data also miRNA expression is dynamic, with respect to both the two incisor segments investigated and to the developmental stage of the incisor.
Project description:Intestinal stem cells (ISCs) are responsible for maintaining the physiological function of the intestinal epithelium through the production of differentiated absorptive and secretory cellular lineages. In addition to producing specialized functional cells, ISCs must also drive constant proliferation in order to maintain the especially high rate of cellular turnover in the intestinal epithelium, which undergoes near total renewal every 5-7 days. Understanding the transcriptional mechanisms that control how ISCs and transit-amplifying progenitors (TAs) balance differentiation and proliferation in the intestine may provide valuable insight into common pathologies, such as inflammatory bowel disease and cancer. Here, we show that the Sry¬¬-box containing transcription factor, Sox4, is involved in the regulation of proliferation in the ISC/TA zone, the expression of ISC-associated genes, and the differentiation of enteroendocrine (EE) cells. Interestingly, we also observed a significant reduction in the expression of the methylcytosine dioxygenase, Tet1, in Sox4-deficient intestines. We find that Tet1, which initiates derepression of target genes via DNA demethylation, is specifically upregulated in ISC populations in wild-type animals. Additionally, Sox4-deficient intestines showed a significant reduction in levels of 5-hydroxymethylcytosine, the catalytic byproduct of TET protein activity, in the ISC/TA zone. Together, our data demonstrate that Sox4 regulates differentiation and proliferation in the intestinal epithelium, and suggests that it may influence these processes through induction of Tet1 and subsequent derepression of target genes through epigenetic mechanisms.
Project description:DLX3 is a homeodomain transcription factor involved in ameloblast differentiation and enamel formation. Mutations in DLX3 in human lead to defects in enamel. However, the downstream targets of Dlx3 transcriptional activity in the enamel organ have not been identified yet. In this study, we compared the transcriptome of enamel organs where Dlx3 has been deleted to control tissues. Total RNA was extracted from enamel organs (mandibular incisors) from Dlx3-WT (N=4) and Dlx3-K14cKO (N=4) mice at P10. cDNA libraries were generated using NEBnext and NuGen kits. Sequencing was performed on the HiSeq2000.
Project description:DLX3 is a homeodomain transcription factor involved in amelogenesis. Mutations in DLX3 in human lead to Tricho-Dento-Osseous syndrome featuring enamel hypoplasia and hypomineralization. Here we investigated the distribution of DLX3 DNA binding sites in rat enamel organ using ChIP-seq.
Project description:Abstarct:Mutations in the endoplasmic reticulum (ER) Ca2+ sensor stromal interaction molecule 1 (STIM1) result is a number of disease states including abnormal enamel formation. However, these defects in enamel have remained unclear given a lack of animal models available. We generated Stim1/2K14Cre mice to ablate the activity of STIM1 and its homologue STIM2 in enamel cells. These mice showed impaired Ca2+ entry in enamel cells and although enamel formed, it was severely hypomineralized and mechanically weak. RNA-sequencing of enamel cells provided a global overview of loss of Ca2+ sensor activity. ER stress markers associated with unfolded protein response (UPR) were increased. Cell morphology was altered showing loss of the typical ruffled-border and mislocalized mitochondria. We also identified decreased glutathione system and potentially associated with this, increased ROS and abnormal mitochondria. The Ca2+ extrusion system and enamel gene expression were also altered. These data might represent the first in vivo study linking Stim1/2 ablation with increased UPR function, decreased glutathione metabolism, increased ROS and abnormal mitochondria. Loss of ER Ca2+ sensors Stim1/2 in enamel cells has substantial detrimental effects at the cell and mineral phase level.
Project description:DLX3 is a homeodomain transcription factor involved in ameloblast differentiation and enamel formation. Mutations in DLX3 in human lead to defects in enamel. However, the downstream targets of Dlx3 transcriptional activity in the enamel organ have not been identified yet. In this study, we compared the transcriptome of enamel organs where Dlx3 has been deleted to control tissues.
Project description:DLX3 is a homeodomain transcription factor involved in ameloblast differentiation and enamel formation. Mutations in DLX3 in human lead to defects in enamel. However, the downstream targets of Dlx3 transcriptional activity in the enamel organ have not been identified yet. In this study, we compared the transcriptome of enamel organs where Dlx3 has been deleted to control tissues.