A regulatory network of Sox and Six transcription factors initiate a cell fate transformation during hearing regeneration in adult zebrafish
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ABSTRACT: Using adult zebrafish inner ears as a model for sensorineural regeneration, we performed a targeted ablation of the mechanosensory receptors in the saccule and utricle and characterized the single-cell epigenome and transcriptome at consecutive time-points following hair cell death.
Project description:Using adult zebrafish inner ears as a model for sensorineural regeneration, we ablated the mechanosensory receptors and characterized the single-cell epigenome and transcriptome at consecutive time points during hair cell regeneration. We utilized deep learning on the regeneration-induced open chromatin sequences and identified cell-specific transcription factor (TF) motif patterns. Enhancer activity correlated with gene expression and identified potential gene regulatory networks. A pattern of overlapping Sox- and Six-family TF gene expression and binding motifs was detected, suggesting a combinatorial program of TFs driving regeneration and cell identity. Pseudotime analysis of single-cell transcriptomic data suggested that support cells within the sensory epithelium changed cell identity to a "progenitor" cell population that could differentiate into hair cells. We identified a 2.6 kb DNA enhancer upstream of the sox2 promoter that, when deleted, showed a dominant phenotype that resulted in a hair-cell-regeneration-specific deficit in both the lateral line and adult inner ear.
Project description:A major cause of human deafness and vestibular dysfunction is permanent loss of the mechanosensory hair cells of the inner ear. In non-mammalian vertebrates such as zebrafish, regeneration of missing hair cells can occur throughout life. While a comparative approach has the potential to reveal the basis of such differential regenerative ability, the degree to which the inner ears of fish and mammals share common hair and supporting cell types remains unresolved. Here we perform single-cell RNA sequencing of the zebrafish inner ear at embryonic through adult stages to catalog the diversity of hair and non-sensory supporting cells. We identify a putative progenitor population for hair and supporting cells, as well as distinct hair and supporting cell types in the maculae versus cristae. The hair and supporting cell types differ from those described for the lateral line, a distributed mechanosensory organ in zebrafish in which most studies of hair cell regeneration have been conducted. In the maculae, we identify two subtypes of hair cells that share gene expression with mammalian striolar or extrastriolar hair cells. In situ hybridization reveals that these hair cell subtypes occupy distinct spatial domains within the two major macular organs, the utricle and saccule, consistent with the reported distinct electrophysiological properties of hair cells within these domains. These findings suggest that primitive specialization of spatially distinct striolar and extrastriolar hair cells likely arose in the last common ancestor of fish and mammals. The similarities of inner ear cell type composition between fish and mammals also support using zebrafish as a relevant model for understanding inner ear-specific hair cell function and regeneration.
Project description:The otolith organs of the inner ear consist of the utricle and saccule that detect linear acceleration. These organs rely on mechanosensitive hair cells for transduction of signals to the central nervous system. In the murine utricle, about half of the hair cells are born during the first postnatal week. Here, we report diverse cell-cell crosstalk among the 12 annotated cell populations in the developing neonatal utricle, including epithelial and non-epithelial cellular signaling. The mesenchymal cells are the dominant signal senders during the postnatal period. Epithelial to mesenchymal signaling, as well as mesenchymal to epithelial signaling, are quantitatively shown through the TGFβ and Pleiotrophin pathways. This study highlights the dynamic process of postnatal vestibular organ development that relies not only on epithelial cells, but also on crosstalk between spatial compartments and among different cell groups.
Project description:Purified utricle hair bundles and utricular epithelium from P3-P7 rat 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 mass spectrometer for protein detection.
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.
Project description:The inner ear in mammals is derived from a simple ectodermal thickening called the otic placode. Through a series of complex morphological changes, the placode forms the mature inner ear comprising of the auditory organ (cochlea) and the vestibular/balance organs (utricle, saccule, and three semi-circular canals). The vast majority of genes known to be involved during inner ear development have been found through mutational screens or by chance. To identify genes that can serve as novel candidates required for inner ear development, and also candidate genes for uncloned human deafnesses, inner ear tissues from mouse embryos from E9 to E15 were microdissected and expression-profiled at half-day intervals. Also profiled was the non-inner ear mesenchymal tissue surrounding the inner ear tissue. Various patterns of gene expression were identified, and significant biological pathways that these genes represented were identified. Also identified were mouse genes whose human orthologs are located within uncloned non-syndromic deafness intervals, thus serving as candidates for sequence analysis. Experiment Overall Design: Inner ear tissues from E9 to E15 were microdissected at half-day intervals. E9 is the earliest stage when the otic placode is clearly visible and able to be microdissected cleanly. E15 is the stage when all the organs of the inner ear have become established, as have the sensory hair and non-sensory support cells within those organs. For each of the stages from E9 to E10, whole inner ears were profiled. For each of the stages from E10.5 to E12, the primordial cochlear and vestibular organs were profiled separately. For each of the stages from E12.5 to E15, the cochlea and the saccule were profiled separately, whereas the utricle and the three ampullae were combined and profiled together. Any given tissue from any given stage was a collection of anywhere between 4 to 17 identical tissues, and was obtained in duplicate (i.e. from different litters). Hence, a total of 58 inner ear samples were obtained. Moreover, non-inner ear tissue found in the immediate vicinity of inner ear tissue was also obtained and profiled. Specifically, all non-inner ear tissue from E9 was profiled in duplicate. Non-inner ear tissue from E9.5 to E10.5 was pooled and profiled together (in duplicate), whereas that from E11 to E15 was pooled and profiled together (also in duplicate). Therefore, a total of 6 non-inner samples were obtained.
Project description:We have employed a novel approach for the identification of functionally important microRNA (miRNA)-target interactions using integrated miRNA, transcriptome and proteome profiles with advanced in silico analysis. By looking at both the transcript and protein levels of expression, a thorough coverage of miRNA regulation was obtained. Microdissected auditory and vestibular sensory epithelia were used as the model system, thus being the first time such a comparison was carried out in a neuroepithelial system. Moreover, this is one of only a few studies employing proteome screening for the identification of miRNA targets. Notably, this approach can be employed for the study of other tissues and organs. We detected the expression of 157 miRNAs in the inner ear sensory epithelia, with 53 miRNAs differentially expressed between the cochlea and vestibule. By searching for enrichment and depletion of miRNA targets in the transcript and protein datasets with a reciprocal or similar expression, respectively, as the regulatory miRNA, we identified functionally important miRNAs. Finally, the interaction between miR-135b and PSIP1-P75, a transcriptional coacitvator previously unknown in the inner ear, was identified and validated experimentally. We suggest that miR-135b may serve as a cellular effector, involved in regulating some of the differences between the cochlear and vestibular hair cells. We investigated the mRNA expression profile of the cochlear and vestibular sensory epithelia from inner ears of postnatal day 2 mice using the Affymetrix GeneChip® 430 2Mouse Genome array. Cochlear and vestibular sensory epithelia were dissected from wild type C3H mice and collected separately. The vestibular epithelia consisted of the saccule, utricle and the lateral and anterior cristae. Both the cochlear and vestibular sensory epithelia were dissected with their underlying mesenchyma. Altogether three pools, three biological replicates, of each tissue type were collected consisting of cochlear or vestibular sensory epithelia dissected from 10 to 12 inner ears.
Project description:To understand the basic biological property of hair cells (HCs) from lower vertebrates, we examined transcriptomes of adult zebrafish HCs. GFP-labeled HCs were isolated from the utricle, saccule, and lagena, the three inner-ear sensory epithelia of a pou4f3 promoter-driven GAP-GFP line of transgenic zebrafish. 2,000 HCs and 2,000 non-sensory cells from the inner ear were individually collected by suction pipet technique. RNA sequencing was performed and the resulting sequences were mapped, analyzed, and compared. Comparisons allow us to identify enriched genes in HCs, which may underlie HC specialization.
Project description:A regulatory network of Sox and Six transcription factors initiate a cell fate transformation during hearing regeneration in adult zebrafish
Project description:Activating transcription factor 6 (Atf6) is a key regulator of the unfolded protein response (UPR) and is important for endoplasmic reticulum (ER) function and protein homeostasis in metazoan cells. Patients carrying loss-of-function ATF6 disease alleles develop the cone dysfunction disorder, achromatopsia. The impact of loss of ATF6 function on other cell types, organs, and diseases in people remains unclear. Here, we reported that progressive sensorineural hearing loss was a notable complaint in some patients carrying ATF6 disease alleles and that Atf6-/- mice also showed progressive auditory deficits affecting both genders. In mice with hearing deficits, we found disorganized stereocilia on hair cells and focal loss of outer hair cells. Transcriptomic analysis of Atf6-/- cochleae revealed marked induction of UPR, especially through the PERK arm. These findings identify ATF6 as an essential regulator of cochlear health and function. Furthermore, they supported that ATF6 inactivation in people causes progressive sensorineural hearing loss as part of a blindness-deafness genetic syndrome targeting hair cells and cone photoreceptors. Lastly, our genetic findings support ER stress as an important pathomechanism underlying cochlear damage and hearing loss with clinical implications for patient lifestyle modifications that minimize environmental/physiologic sources of ER stress to the ear.