Project description:The classical model posits that a small number of quiescent stem cells (SCs) gives rise to proliferating transit-amplifying cells before terminal differentiation. However, recent evidence indicates that some tissues house multiple progenitor pools with distinct proliferative and differentiation potentials. Resolving the identity and spatial organization of these populations is therefore a fundamental requirement for understanding tissue renewal. Here, using a combination of single-cell RNA sequencing (scRNAseq), mouse genetics, and tissue injury approaches, we uncovered cellular hierarchies and mechanisms underlying the maintenance and repair of the ever-growing mouse incisor, an ectodermal appendage model system that requires high cell turnover for its homeostasis and quick healing capability. We found that during homeostasis, a group of actively cycling epithelial progenitors generates both the enamel-producing ameloblasts and the adjacent non-ameloblast cell layers, which were previously proposed to be quiescent SCs. Upon injury, transient adjustments to the proliferation kinetics of dental epithelial progenitor cells compensated for cell loss. Injury repair was also supported by direct conversion of supporting Notch1-expressing cells to ameloblasts. Our elucidation of epithelial SC identity, position, and function thus provides a mechanistic basis for the homeostasis and repair of a fast-turnover ectodermal appendage and illustrates how a cycling progenitor pool confers considerable epithelial plasticity during tissue renewal.
Project description:The classical model of tissue renewal posits that small numbers of quiescent stem cells (SCs) give rise to proliferating transit-amplifying cells before terminal differentiation. However, many organs house pools of SCs with proliferative and differentiation potentials that diverge from this template. Resolving SC identity and organization is therefore central to understanding tissue renewal. Here, using a combination of single-cell RNA sequencing (scRNA-seq), mouse genetics and tissue injury approaches, we uncover cellular hierarchies and mechanisms that underlie the maintenance and repair of the continuously growing mouse incisor. Our results reveal that, during homeostasis, a group of actively cycling epithelial progenitors generates enamel-producing ameloblasts and adjacent layers of non-ameloblast cells. After injury, tissue repair was achieved through transient increases in progenitor-cell proliferation and through direct conversion of Notch1-expressing cells to ameloblasts. We elucidate epithelial SC identity, position and function, providing a mechanistic basis for the homeostasis and repair of a fast-turnover ectodermal appendage.
Project description:Biological adhesion (bioadhesion) is referred to attachment of organisms to either biotic or abiotic surfaces. The differentiated ectodermal basal disc cells of the freshwater cnidarian Hydra secrete proteinaceous glue to temporarily attach themselves to surfaces underwater. In this study, we investigate for the first time the protein content of adhesive secretions from the freshwater cnidarian Hydra magnipapillata strain 105. This secretome were analysed using mass spectrometry and resulting MS/MS data were searched against in silico translated H. magnipapillata transcriptome and results from gene expression.
Project description:To examine biological changes and regionality dictating structural remodelling in Atrial Fibrillation, we performed NanoString GeoMx Digital Spatial Profiling (DSP) of tissue biopsies from AF and SR patients. Regions were selected from adipose tissue and atrail appendage tissue close or far apart from tissue interphase.
Project description:The response of ectodermal explants, neuralized by noggin and treated with cycloheximide, following activation of hormone-inducible zic1 injected into the parent embryos compared to those from beta globin injected embryos as controls, is expected to provide information on the direct targets of the Zic1 transcription factor. Experiment Overall Design: Activation of zic1 in ectodermal explants following inhibition of new protein synthesis allowed the direct targets of zic1 to be identified by comparison with controls. After RNA extraction, purification and checks with PCR with actin primers for any mesoderm contamination samples were prepared for hybridization to Xenopus laevis Affymetrix GeneChip arrays.
Project description:Vertebrate Hox genes are key players in the establishment of structures during the development of the main body axis. Subsequently, they play important roles either in organizing secondary axial structures such as the appendages, or during homeostasis in postnatal stages and adulthood. Here we set up to analyze their elusive function in the ectodermal compartment, using the mouse limb bud as a model. We report that the HoxC gene cluster was globally co-opted to be transcribed in the distal limb ectoderm, where it is activated following the rule of temporal colinearity. These ectodermal cells subsequently produce various keratinized organs such as nails or claws. Accordingly, deletion of the HoxC cluster led to mice lacking nails (anonychia) and also hairs (alopecia), a condition stronger than the previously reported loss of function of Hoxc13, which is causative of the ectodermal dysplasia 9 (ECTD9) syndrome in human patients. We further identified, in mammals only, two ectodermal-specific enhancers located upstream the gene cluster, which act synergistically to regulate Hoxc genes in these ectodermal organs. Deletion of these enhancers alone or in combination revealed a strong quantitative component in the regulation of these genes in the ectoderm, suggesting that these two enhancers may have evolved along with mammals to provide the level of HOXC proteins necessary for the full development of hairs and nails.