Project description:Otic ectoderm gives rise to almost all cell types of the inner ear; however, the mechanisms that link transcription factors, chromatin, lineage commitment and differentiation capacity are largely unknown. Here we show that Brg1 chromatin-remodeling factor is required for specifying neurosensory lineage in the otocyst and for inducing hair and supporting cell fates in the cochlear sensory epithelium. Brg1 interacts with the critical neurosensory-specific transcription factors Eya1/Six1, both of which simultaneously interact with BAF60a or BAF60c. Chromatin immunoprecipitation-sequencing (ChIP-seq) and ChIP assays demonstrate Brg1 association with discrete regulatory elements at the Eya1 and Six1 loci. Brg1-deficiency leads to markedly decreased Brg1 binding at these elements and loss of Eya1 and Six1 expression. Furthermore, ChIP-seq reveals Brg1-bound promoter-proximal and distal regions near genes essential for inner ear morphogenesis and cochlear sensory epithelium development. These findings uncover essential functions for chromatin-remodeling in the activation of neurosensory fates during inner ear development.
Project description:We report on the gene expression changes associated with Lats1/2 inhibition in supporting cells of the vestibular inner ear sensory epithelium
Project description:MicroRNAs (miRNAs) inhibit the translation of target mRNAs and affect, directly or indirectly, the expression of a large portion of the protein-coding genes. This study focuses on miRNAs that are expressed in the mouse cochlea and vestibule, the two inner ear compartments. To identify miRNAs that are expressed in the vertebrate developing inner ear, we used miRNA microarrays. Similar miRNA profiles were found in newborn (P0) mouse whole cochleae and vestibules. 105 miRNAs were found to be expressed in the whole P0 cochlea and 114 miRNAs expressed in the whole P0 vestibule with average intensities higher than twice the global background, out of 206 included in the arrays. Only 24 miRNAs were found to have different levels of expression in these whole organs, and these differences were mild (15-40%). The microarray results were intersected with two bioinformatic complementary approaches in order to choose candidate miRNAs that are predicted to be expressed specifically in the inner ear sensory epithelia (see the paper).
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:The molecular characterization of early stages of human inner ear development is limited by the difficulty in accessing samples at early gestational stages. Some aspects of inner ear morphogenesis can be recapitulated using pluripotent stem cell directed differentiation in inner ear organoids (IEOs). Once validated and benchmarked, these models could provide a unique tool to complement and refine our understanding of human otic differentiation and could be used to model developmental defects.Here we provide a first characterization of early human embryonic otocyst development and compare the primary tissue to the iPSC-derived inner ear cell types. Multiplex immunostaining and single cell RNA sequencing were used to characterize human iPSC-derived IEOs at 3 key developmental steps, providing a new and unique signature of in vitro derived otic- placode, epithelium, neuroblasts and sensory epithelia. The expression and localization of key markers were further evaluated in human embryos. We show that the otic placode derived in vitro (day 8-12) matches marker expression of Carnegie Stage (CS) 11 embryos, and subsequently (day 20-40) gives rise to otic epithelia and neuroblasts comparable to the CS13 embryonic stage. Differentiation of sensory epithelia, including supporting cells and hair cells, starts in vitro at day 50-60 of culture. The maturity of these cells is equivalent to vestibular sensory epithelia at week 10 or cochlear tissue at week 12 of development, prior to functional onset. Taken together these data indicates that the current state of the art protocol enables the specification of bona fide otic tissue, supporting further application of IEOs to model inner ear biology and disease
Project description:Retinoblastoma gene (Rb1) is required for proper cell cycle exit in the developing mouse inner ear and its deletion in the embryo leads to proliferation of sensory progenitor cells that differentiate into hair cells and supporting cells. In the Pou4f3-Cre:Rb1 flox/flox (Rb1 cKO) inner ear, utricular hair cells differentiate and survive into adulthood whereas differentiation and survival of cochlear hair cells are impaired. To comprehensively survey the pRb pathway in the mammalian inner ear, we performed microarray analysis of Rb1 cKO cochlea and utricle. P6 or 2-month control and Rb1 cKO littermates were euthanized and the inner ear tissues were dissected. Total RNA was extracted from the pooled samples. Technical duplicates of the pooled RNA were used for microarray.
Project description:Retinoblastoma gene (Rb1) is required for proper cell cycle exit in the developing mouse inner ear and its deletion in the embryo leads to proliferation of sensory progenitor cells that differentiate into hair cells and supporting cells. In the Pou4f3-Cre:Rb1 flox/flox (Rb1 cKO) inner ear, utricular hair cells differentiate and survive into adulthood whereas differentiation and survival of cochlear hair cells are impaired. To comprehensively survey the pRb pathway in the mammalian inner ear, we performed microarray analysis of Rb1 cKO cochlea and utricle.
Project description:In the inner ear, cochlear and vestibular sensory epithelia utilize grossly similar cell types to transduce different stimuli: sound and acceleration. Each individual sensory epithelium is composed of highly heterogeneous populations of cells based on physiological and anatomical criteria. However, limited numbers of each cell type have impeded transcriptional characterization. Here we generated transcriptomes for 301 single cells from the utricular and cochlear sensory epithelia of newborn mice to circumvent this challenge. Cluster analysis indicates distinct profiles for each of the major sensory epithelial cell types, as well as less distinct subpopulations. Asynchrony within utricles allows reconstruction of the temporal progression of cell-type specific differentiation and suggests possible plasticity among cells at the sensory-nonsensory boundary. Comparisons of cell types from utricles and cochleae demonstrate divergence between auditory and vestibular cells despite a common origin. These results provide significant insights into the developmental processes that form unique inner ear cell types.
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.