Fgf8 genetic labeling reveals the early specification of vestibular hair cell type in mouse utricle.
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ABSTRACT:
SUBMITTER: Ratzan EM
PROVIDER: S-EPMC7687870 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The mouse utricle model system is the best-characterized ex vivo preparation for studies of mature mammalian hair cells (HCs). Despite the many advantages of this model system, efficient and reliable quantification of HCs from cultured utricles has been a persistent challenge with this model system. Utricular HCs are commonly quantified by counting immunolabeled HCs in regions of interest (ROIs) placed over an image of the utricle. Our data indicate that the accuracy of HC counts obtained using this method can be impacted by variability in HC density across different regions of the utricle. In addition, the commonly used HC marker myosin 7a results in a diffuse cytoplasmic stain that is not conducive to automated quantification and must be quantified manually, a labor-intensive task. Furthermore, myosin 7a immunoreactivity is retained in dead HCs, resulting in inaccurate quantification of live HCs using this marker. Here we have developed a method for semi-automated quantification of surviving HCs that combines immunoreactivity for the HC-specific transcription factor Pou4f3 with labeling of activated caspase 3/7 (AC3/7) to detect apoptotic HCs. The discrete nuclear Pou4f3 signal allowed us to utilize the binary or threshold function within ImageJ to automate HC quantification. To further streamline this process, we created an ImageJ macro that automates the process from raw image loading to a final quantified image that can be immediately evaluated for accuracy. Within this quantified image, the user can manually correct the quantification via an image overlay indicating the counted HC nuclei. Pou4f3-positive HCs that also express AC3/7 are subtracted to yield accurate counts of surviving HCs. Overall, we present a semi-automated method that is faster than manual HC quantification and identifies surviving HCs with high accuracy.
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Project description:Damage-activated stem/progenitor cells play important roles in regenerating lost cells and in tissue repair. Previous studies reported that the mouse utricle has limited hair cell regeneration ability after hair cell ablation. However, the potential progenitor cell population regenerating new hair cells remains undiscovered. In this study, we first found that Lgr5, a Wnt target gene that is not usually expressed in the neonatal mouse utricle, can be activated by 24 h neomycin treatment in a sub-population of supporting cells in the striolar region of the neonatal mouse utricle. Lineage tracing demonstrated that these Lgr5-positive supporting cells could regenerate new hair cells in explant culture. We isolated the damage-activated Lgr5-positive cells with flow cytometry and found that these Lgr5-positive supporting cells could regenerate hair cells in vitro, and self-renew to form spheres, which maintained the capacity to differentiate into hair cells over seven generations of passages. Our results suggest that damage-activated Lgr5-positive supporting cells act as hair cell progenitors in the neonatal mouse utricle, which may help to uncover a potential route to regenerate hair cell in mammals.
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Project description:Notch signaling is active during the development of mosaic epithelial sheets and during their turnover and regeneration. After the loss of hair cells in the mosaic sheet of the vestibular sensory epithelium, new hair cells can be spontaneously generated by transdifferentiation of supporting cells. This regenerative process involves downregulation of the Hes5 gene and is known to be limited and incomplete, especially when the lesion is severe. Here, we test whether further downregulation of Hes5 gene accomplished by the use of siRNA after a severe lesion induced by an aminoglycoside in the mouse utricle can enhance the transdifferentiation of supporting cells and lead to the increased production of new hair cells. We demonstrate that Hes5 levels in the utricle decreased after the application of siRNA and that the number of hair cells in these utricles was significantly larger than following control treatment. The data suggest that siRNA technology may be useful for inducing repair and regeneration in the inner ear and that the Notch signaling pathway is a potentially useful target for specific gene expression inhibition.
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Project description:Recruitment of endogenous progenitors is critical during tissue repair. The inner ear utricle requires mechanosensory hair cells (HCs) to detect linear acceleration. After damage, non-mammalian utricles regenerate HCs via both proliferation and direct transdifferentiation. In adult mammals, limited transdifferentiation from unidentified progenitors occurs to regenerate extrastriolar Type II HCs. Here we show that HC damage in neonatal mouse utricle activates the Wnt target gene Lgr5 in striolar supporting cells. Lineage tracing and time-lapse microscopy reveal that Lgr5+ cells transdifferentiate into HC-like cells in vitro. In contrast to adults, HC ablation in neonatal utricles in vivo recruits Lgr5+ cells to regenerate striolar HCs through mitotic and transdifferentiation pathways. Both Type I and II HCs are regenerated, and regenerated HCs display stereocilia and synapses. Lastly, stabilized ß-catenin in Lgr5+ cells enhances mitotic activity and HC regeneration. Thus Lgr5 marks Wnt-regulated, damage-activated HC progenitors and may help uncover factors driving mammalian HC regeneration.
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Project description:Development of the vertebrate hair bundle is a precisely orchestrated event that culminates in production of a tightly ordered arrangement of actin-rich stereocilia and a single axonemal kinocilium. To understand how the protein composition of the bundle changes during development, we isolated bundles from young (postnatal days P4-P6) and mature (P21-P25) mouse utricles using the twist-off method, then characterized their constituent proteins using liquid-chromatography tandem mass spectrometry with data-dependent acquisition. Using MaxQuant and label-free quantitation, we measured relative abundances of proteins in both bundles and in the whole utricle; comparison of protein abundance between the two fractions allows calculation of enrichment in bundles. These data, which are available via ProteomeXchange with identifier PXD002167, will be useful for examining the proteins present in mammalian vestibular bundles and how their concentrations change over development.
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Project description:This SuperSeries is composed of the SubSeries listed below.
2024-09-24 | GSE251854 | GEO
Project description:The mammalian cochlea loses its ability to regenerate new hair cells prior to the onset of hearing. In contrast, the adult vestibular system can produce new hair cells in response to damage, or by reprogramming of supporting cells with the hair cell transcription factor Atoh1. We used RNA-seq and ATAC-seq to probe the transcriptional and epigenetic responses of utricle supporting cells to damage and Atoh1 transduction. We show that the regenerative response of the utricle correlates with a more accessible chromatin structure in utricle supporting cells compared to their cochlear counterparts. We also provide evidence that Atoh1 transduction of supporting cells is able to promote increased transcriptional accessibility of some hair cell genes. Our study offers a possible explanation for regenerative differences between sensory organs of the inner ear, but shows that additional factors to Atoh1 may be required for optimal reprogramming of hair cell fate.
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Project description:Proteomic analysis of chick vestibualr hair bundles purified using the twist-off method. See Description.doc. Utricle hair bundles were purified from E20–21 chicks using the twist-off method (Gillespie & Hudspeth J Cell Biol 112, 625-640, 1991; Shin et al. Neuron 53, 371-386, 2007). NuPAGE LDS sample buffer (Invitrogen) with 50 mM dithiothreitol was added to a combined final volume of 80 µl per 100 utricles' worth of bundles; samples were heated to 70°C for 15 min. Epithelial proteins were similarly solubilized with sample buffer. Proteins were separated by running ~1 cm into a NuPAGE 4–12% Bis-Tris gel (1.5 mm x 10 well; one or two lanes per bundle sample); gels were rinsed with water, then stained with Imperial Protein Stain (Thermo Scientific). The 1 cm of gel with separated proteins was manually sliced into six pieces. Gel pieces were transferred to siliconized tubes and washed and destained in 200 µl 50% methanol overnight. The gel pieces were dehydrated in acetonitrile, rehydrated in 30 µl of 10 mM dithiothreitol in 0.1 M ammonium bicarbonate and reduced at room temperature for 0.5 h. The DTT solution was removed and the sample alkylated in 30 µl 50 mM iodoacetamide in 0.1 M ammonium bicarbonate at room temperature for 0.5 h. The reagent was removed and the gel pieces dehydrated in 100 µl acetonitrile. The acetonitrile was removed and the gel pieces rehydrated in 100 µl 0.1 M ammonium bicarbonate. The pieces were dehydrated in 100 µl acetonitrile, the acetonitrile removed and the pieces completely dried by vacuum centrifugation. The gel pieces were rehydrated in 20 ng/µl trypsin (Sigma-Aldrich T6567 proteomics grade, from porcine pancreas, dimethylated) in 50 mM ammonium bicarbonate on ice for 10 min. Any excess enzyme solution was removed and 20 µl 50 mM ammonium bicarbonate added. The sample was digested overnight at 37°C and the peptides formed extracted from the polyacrylamide in two 30 µl aliquots of 50% acetonitrile/5% formic acid. These extracts were combined and evaporated to 15 µl for MS analysis. For the gel slice immediately adjacent to the agarose, peptides were purified away from interfering polymers by SCX. A single experiment's worth of hair bundles or epithelium was analyzed by six LC-MS/MS runs, corresponding to the six gel pieces. The LC-MS/MS system consisted of a Thermo Electron Orbitrap Velos ETD mass spectrometer system with a Protana nanospray ion source, which was interfaced to a reversed-phase capillary column of 8 cm length x 75 µm internal diameter, self-packed with Phenomenex C18 Jupiter of 10 µm particle size. An extract aliquot (7.5 µl) was injected and peptides eluted from the column by an acetonitrile/0.1 M acetic acid gradient at a flow rate of 0.5 µl/min over 1.2 hr. The nanospray ion source was operated at 2.5 kV. The digest was analyzed using the data-dependent capability of the instrument, acquiring—in sequential scans—a single full scan mass spectrum in the Orbitrap detector at 60,000 resolution to determine peptide molecular weights, and 20 product-ion spectra in the ion trap to determine amino acid sequence. MaxQuant version 1.2.2.5 software was used for protein identification and quantitation. The default contaminants file associated with the MaxQuant download was edited to remove entries known to be present in hair bundles (e.g., actin) and to add additional impurities that entered the bundle-purification workflow (keratins, hemoglobins, egg white components). Mass spectrometry data were searched against Ensembl version 66 (released February, 2012) using Andromeda; the Ensembl FASTA file was edited by replacing several sequences with longer or full-length sequences, including actin gamma 1 (NP_001007825.1), actin beta (NP_990849.1), fascin 1 (NP_001171603), fascin 2 (NP_001171209), ATP synthase beta (NP_001026562.1), peptidylprolyl isomerase A (NP_001159798.1), calbindin 2 (NP_990647.1), PDZD7 (XP_003641537.1), espin (XP_417532.3), and CACNA2D2 (XP_427707.3). Protein identifications were reported with an FDR of 1%. If a set of peptides for a protein was identical to or completely contained within that of another protein, MaxQuant groups those proteins together ("redundant groups"); the entry with the largest number of peptides was used to identify the redundant group. Redundant groups that shared more than 20% of their identified peptides were further grouped in our analysis ("shared-peptide groups"); the entry with the greatest intensity associated with it was used to identify the shared-peptide group.
2013-01-08 | PXD000104 | Pride
Project description:ATP-utilizing enzymes play key roles in hair bundles, the mechanically sensitive organelles of sensory hair cells in the inner ear. We used a fluorescent ATP analog, EDA-ATP-Cy3 (Cy3-ATP), to label ATP-binding proteins in two different preparations of unfixed hair-cell stereocilia of the mouse. In the first preparation, we lightly permeabilized dissected cochleas, then labeled them with Cy3-ATP. Hair cells and their stereocilia remained intact, and stereocilia tips in rows 1 and 2 were labeled particularly strongly with Cy3-ATP. In many cases, vanadate (Vi) traps nucleotides at the active site of myosin isoforms and presents nucleotide dissociation. Co-application with Vi enhanced the tip labeling, which is consistent with myosin isoforms being responsible. By contrast, the actin polymerization inhibitors latrunculin A and cytochalasin D had no effect, suggesting that actin turnover at stereocilia tips was not involved. Cy3-ATP labeling was substantially reduced-but did not disappear altogether-in mutant cochleas lacking MYO15A; by contrast, labeling remained robust in cochleas lacking MYO7A. In the second preparation, used to quantify Cy3-ATP labeling, we labeled vestibular stereocilia that had been adsorbed to glass, which demonstrated that tip labeling was higher in longer stereocilia. We found that tip signal was reduced by ~ 50% in Myo15ash2/sh2 stereocilia as compared to Myo15ash2/+stereocilia. These results suggest that MYO15A accounts for a substantial fraction of the Cy3-ATP tip labeling in vestibular hair cells, and so this novel preparation could be utilized to examine the control of MYO15A ATPase activity in situ.
| S-EPMC8668996 | biostudies-literature
Project description:Purified utricle hair bundles and utricular epithelium from P21-P25 mouse inner ears were analyzed by LC-MS/MS to determine the abundant and enriched proteins of the hair bundle. This dataset used a Thermo LTQ Velos mass spectrometer for protein detection.
2015-11-17 | PXD002415 | Pride