Project description:Loss of sensory hair cells leads to deafness and balance deficiencies. In contrast to mammalian hair cells, zebrafish ear and lateral line hair cells regenerate from poorly characterized, proliferating support cells. Equally ill-defined is the gene regulatory network underlying the progression of support cells to cycling hair cell progenitors and differentiated hair cells. We used single-cell RNA-Sequencing (scRNA-Seq) of lateral line sensory organs and uncovered five different support cell types, including quiescent and activated stem cells. In silico ordering of support cells along a developmental trajectory identified cells that self-renew and new groups of genes required for hair cell differentiation. scRNA-Seq analyses of fgf3 mutants, in which hair cell regeneration is increased demonstrates that Fgf and Notch signaling inhibit proliferation of support cells in parallel by inhibiting Wnt signaling. Our scRNA-Seq analyses set the foundation for mechanistic studies of sensory organ regeneration and is crucial for identifying factors to trigger hair cell production in mammals.
Project description:Latent transdifferentiation potential exists in supporting cells at neonatal stage in the organ of Corti in mouse, but this plasticity is lost rapidly during the first week of postnatal maturation, leading to the failure of sensory hair cell regeneration. To investigate the molecular mechanism underlying the loss of transdifferentiation potential, we compared epigenetic changes in E17.5, P1 and P6 supporting cells. In E17.5 and P1 supporting cells, hair cell gene enhancers are kept in a primed state (H3K4me1+ H3K27ac-) which can be readily activated during transdifferentiation induced by Notch blocking. As supporting cells mature, a substantial amount of hair cell gene enhancers are decommissioned by H3K4me1, leading to the loss of transdifferentiation potential. In contrast, hair cell gene enhancers retain their commissioned epigenetic status in mature utricular supporting cells, sustaining the transidifferentiation potential in utricular supporting cells in mature animals. Our findings reveal the epigenetic mechanisms underlying the failure of sensory hair cell regeneration in mammalian cochlea.
Project description:Purpose: This study aimed to explore the mechanism of SBM to promote hair regeneration through single-cell transcriptomics Methods: Supplementation with intragastric administration or smear administration of SBM in artificially shaved C57BL/6 mice to observe its hair growth. Single-cell RNA sequencing were performed to explore the role of SBM for hair regeneration. Results: SBM significantly induced hair growth compared with control treatment.The results of single-cell sequencing revealed that after SBM treatment, the number of hair follicle stem cells (HFSCs) and dermal papilla cells (DPCs) increased significantly. Cell interactions and volcano maps show that interaction of FGF signaling pathway was significantly enhanced, in which FGF7 expression was especially upregulated in DPCs. In addition, Wnt signaling pathway also had a partially enhanced effect on the interactions between various cells in the skin. Network pharmacology study showed that the promotion of FGF and Wnt pathways by SBM was also enriched in alopecia diseases. Conclusion: We report that SBM has a potential effect on the promotion of hair growth by mainly activating FGF signaling pathway. The use of SBM may be a novel therapeutic option for hair loss.
Project description:Sensorineural hearing loss is included in the most common disabilities, and often caused by loss of sensory hair cells in the cochlea. Hair cell regeneration has long been a main target for developing novel therapeutics for sensorineural hearing loss. In the mammalian cochlea, hair cell regeneration occurs in very limited situations, while auditory epithelia of non-mammalians retain the capacity for hair cell regeneration. In the avian basilar papilla, an auditory sensory epithelium, supporting cells, which are sources for regenerated hair cells, are usually quiescent, while hair cell loss induces both direct transdifferentiation of supporting cells and mitotic division of supporting cells. In the present study, we aimed to establish an explant culture model for hair cell regeneration in chick basilar papillae, and validated usefulness of our model to investigate the initial phase of hair cell regeneration. Histological assessments demonstrated that hair cell regeneration via direct transdifferentiation of supporting cells occurred in our model. Labeling assay using 5-ethynyl-2'-deoxyuridine (EdU) revealed the occurrence of mitotic division of supporting cells in the specific location in basilar papillae, while no EdU labeling was identified in newly generated HCs. RNA sequencing indicated alterations in known signaling pathways associated with hair cell regeneration, which is consistent with previous findings. In addition, unbiased analyses of RNA sequencing data indicated novel genes and signaling pathways that could be related to the ignition of supporting cell activation in chick basilar papillae. These results indicate the advantages of our model using explant cultures of chick basilar papillae for exploring molecular mechanisms for hair cell regeneration. Further studies such as single-cell RNA sequencing will allow us to capture the spatiotemporal information by using our explant culture model.
Project description:Deafness due to the terminal loss of inner ear hair cells is one of the most common sensory diseases. However, non-mammalian animals (e.g. birds, amphibian and fish) regenerate damaged hair cells. In order to better understand the reasons underpinning such regeneration disparities in vertebrates, we set out to define the changes in gene expression associated with the regeneration of hair cells in the zebrafish lateral line at high resolution. We performed RNA-Seq analyses on regenerating support cells purified by fluorescence activated cell sorting (FACS). The zebrafish lateral line provides an experimentally accessible system to define the complex signaling events triggered by injury and regeneration, because these cells can be acutely killed by exposure to neomycin, after which they regenerate rapidly. Lateral line hair cells are located in the center of a mechanosensory organ known as the neuromast and are surrounded by inner support cells and an outer ring of mantle cells. Tg(sqET20) larvae express GFP strongly in mantle cells and to a lesser degree in inner support cells. We isolated GFP positive and GFP negative cells from 5 days post fertilization (dpf) Tg(sqET20) larvae at 1, 3 and 5 hours post neomycin treatment, as well as from a non-treated control. Transgenic zebrafish Tg(sqET20) larvae at 5 days post fertilization were exposed to neomycin, dissociated, and FACS sorted into GFP positive and GFP negative populations at 1, 3, and 5 hours following treatment, along with a mock treated 1 hr control. The experiment was performed in triplicate, for a total of 24 samples.
Project description:Hearing loss is most commonly caused by the destruction of mechanosensory hair cells in the ear. This condition is usually permanent: Despite the presence of putative hair-cell progenitors in the cochlea, hair cells are not naturally replenished in adult mammals. Unlike those of the mammalian ear, the progenitor cells of nonmammalian vertebrates can regenerate hair cells through- out life. The basis of this difference remains largely unexplored but may lie in molecular dissimilarities that affect how progenitors respond to hair-cell death. We analyzed gene expression in hair-cell progenitors of the lateral-line system. We developed a transgenic line of zebrafish called alpl:mCherry that expresses a red fluorescent protein in the presumptive hair-cell progenitors known as mantle cells. Fluorescence-activated cell sorting from the skins of transgenic larvae, followed by microarray-based expression analysis, revealed a constellation of transcripts that are specifically enriched in these cells versus hair cells and non-fluorescent skin cells. Gene expression analysis after hair-cell ablation uncovered a cohort of genes that are differentially regulated early in regeneration, suggesting possible roles in the response of progen- itors to hair-cell death. These results provide a resource for studying hair-cell regeneration and the biology of sensory progenitor cells. Two sets of analyses were performed. The first compared baseline expression levels in four sorted cell types from two different transgenic lines of zebrafish, alpl:mCherry;pou4f3:GFP and alpl:mCherry:ET20. alpl:mCherry;pou4f3:GFP larvae express GFP in hair cells and mCherry in mantle cells. alpl:mCherry:ET20 larvae express GFP in most mantle cells and mChery in all mantle cells. The four cell types compared were GFP+ hair cells, mCherry+ mantle cells, mCherry+/GFP+ mantle cells from alpl:mCherry:ET20 larvae, and non-fluorescent (NF) cells. Two hair-cell, five mCherry+ mantle cell, four mCherry+/GFP+ mantle cell, and six NF cell samples were analyzed. This excludes a few samples that were discardced based on failure to cluster by principal component analysis. A second analysis, separately imported, compared gene expression in mCherry+ mantle cells and NF cells at four time points following chemical ablation of hair cells with copper sulfate. These were one, three, five, and eleven hours after treatment (hpCu). Untreated samples served as controls. For mCherry+ cells, five untreated and four each of 1 hpCu, 3 hpCu, 5 hpCu and 11 hpCu were analyzed. For NF cells, six untreated, seven 1 hpCu, and four each of 3 hpCu, 5 hpCu and 11 hpCu samples were analyzed. Untreated mCherry+ and NF cells were shared between both analyses.
Project description:Hearing loss is most commonly caused by the destruction of mechanosensory hair cells in the ear. This condition is usually permanent: Despite the presence of putative hair-cell progenitors in the cochlea, hair cells are not naturally replenished in adult mammals. Unlike those of the mammalian ear, the progenitor cells of nonmammalian vertebrates can regenerate hair cells through- out life. The basis of this difference remains largely unexplored but may lie in molecular dissimilarities that affect how progenitors respond to hair-cell death. We analyzed gene expression in hair-cell progenitors of the lateral-line system. We developed a transgenic line of zebrafish called alpl:mCherry that expresses a red fluorescent protein in the presumptive hair-cell progenitors known as mantle cells. Fluorescence-activated cell sorting from the skins of transgenic larvae, followed by microarray-based expression analysis, revealed a constellation of transcripts that are specifically enriched in these cells versus hair cells and non-fluorescent skin cells. Gene expression analysis after hair-cell ablation uncovered a cohort of genes that are differentially regulated early in regeneration, suggesting possible roles in the response of progen- itors to hair-cell death. These results provide a resource for studying hair-cell regeneration and the biology of sensory progenitor cells.
Project description:Bilaterian animals have evolved complex sensory organs comprised of distinct cell types that function coordinately to sense the environment. Each sensory unit has a defined architecture built from component cell types, including sensory cells, non-sensory support cells, and dedicated sensory neurons. Whether this characteristic cellular composition is present in the sensory organs of non-bilaterian animals is unknown. Here, we interrogate the cell type composition and gene regulatory networks controlling development of the larval apical sensory organ in the sea anemone Nematostella vectensis. Using single cell RNA sequencing and imaging approaches, we reveal two unique cell types in the Nematostella apical sensory organ, GABAergic sensory cells and a putative non-sensory support cell population. Further, we identify the paired-like (PRD) homeodomain gene prd146 as a specific sensory cell marker and show that Prd146+ sensory cells become post-mitotic after gastrulation. Genetic loss of function approaches show that Prd146 is essential for apical sensory organ development. Using a candidate gene knockdown approach, we place prd146 downstream of FGF signaling in the apical sensory organ gene regulatory network. Further, we demonstrate that an aboral FGF activity gradient coordinately regulates the specification of both sensory and support cells. Collectively, these experiments define the genetic basis for apical sensory organ development in a non-bilaterian animal and reveal an unanticipated degree of complexity in a prototypic sensory structure.