Project description:A balance of morphogen gradients during embryogenesis is thought to determine the identity of inner ear end organs. We applied this developmental principle to aggregates of human pluripotent stem cells and found that modulations of Sonic Hedgehog and WNT signaling promote stem cell-derived otic progenitors to express ventral otic markers. Strikingly, these ventralized otic progenitors gave rise to hair cells with short hair bundles comprised of stereocilia arrayed in a geometry reminiscent of cochlear hair cells. Moreover, these ventralized hair cells expressed multiple markers defining outer or inner hair cells in the cochlea. These results reveal that early morphogenic signals are sufficient for not only establishing cochlear gene expression, but also defining structural properties pertaining to the cochlear sensory epithelium.
Project description:Juvenile and mature mouse cochleae contain various low-abundant, vulnerable sensory epithelial cells embedded in the calcified temporal bone, making it challenging to profile the dynamic transcriptome changes of these cells during maturation at the single-cell level. Here we performed the 10X Genomics single-cell RNA sequencing (scRNA-seq) of mouse cochleae at postnatal days 14 (P14) and 28. We attained the transcriptomes of multiple cell types, including hair cells, supporting cells, spiral ganglia, stria fibrocytes, and immune cells. Our hair cell datasets are consistent with published transcripts from bulk RNA seq and scRNA-seq. We also mapped known deafness genes to corresponding cochlear cell types. Importantly, pseudotime trajectory analysis revealed that inner hair cells peak their maturation at P14 while outer hair cells continue to develop until P28. We further identified and confirmed a long noncoding RNA gene Miat expressed during maturation in cochlear hair cells and spiral ganglia neurons. Our transcriptomes of juvenile and mature mouse cochlear cells provided the sequel to those previously published at late embryonic and early postnatal ages and will be valuable resources to investigate cochlear maturation at single-cell resolution.
Project description:Inner ear organoids recapitulate development and are intended to generate cell types of the otic lineage for applications such as basic science research and cell replacement strategies. Here, we use single-cell sequencing to study the cellular heterogeneity of late-stage mouse inner ear organoid sensory epithelia, which we validated by comparison with data sets of the mouse cochlea and vestibular epithelia. We resolved supporting cell sub-types, cochlear like hair cells, and vestibular Type I and Type II like hair cells. While cochlear like hair cells aligned best with an outer hair cell trajectory, vestibular like hair cells followed developmental trajectories similar to in vivo programs branching into Type II and then Type I extrastriolar hair cells. These results highlight the transcriptional accuracy of the organoid developmental program but will also inform future strategies to improve synaptic connectivity and regional specification.
Project description:The hair cells of the cochlea play a decisive role in the process of hearing damage and recovery, yet knowledge of their regeneration process is still limited. Greater epithelial ridge (GER) cells, a type of cell present during cochlear development that has the characteristics of a precursor sensory cell, disappear at the time of maturation of hearing development. Its development and evolution remain mysterious for many years. Here, we performed single-cell RNA sequencing to profile the gene expression landscapes of rats' cochlear duct from P1, P7, and P14 and identified eight major subtypes of GER cells. Furthermore, single-cell trajectory analysis for GER cells and hair cells indicated that among the different subtypes of GER, four subtypes had transient cell proliferation after birth and could transdifferentiate into inner and outer hair cells, and two of them mainly transdifferentiated into inner hair cells. The other two subtypes eventually transdifferentiate into outer hair cells. Our study lays the groundwork for elucidating the mechanisms of the key regulatory genes and signaling pathways in the trans-differentiation of GER cell subtypes into hair cells and provides potential clues to understand hair cell regeneration.
Project description:Hair cells undergo postnatal development that leads to formation of their sensory organelles, synaptic machinery, and in the case of cochlear outer hair cells, their electromotile mechanism. To examine the proteome changes over development, we isolated pools of 5000 Pou4f3-Gfp positive or negative cells from the cochlea or utricles; these cell pools were analyzed by data-dependent and data-independent acquisition (DDA and DIA) mass spectrometry. DDA data were used to generate spectral libraries, which enabled identification and accurate quantitation of specific proteins using the DIA datasets. We also isolated and pooled individual inner and outer hair cells from adult cochlea and compared their proteomes to those of developing hair cells. The DDA and DIA datasets will be valuable for accurately quantifying proteins in hair cells and non-hair cells over this developmental window.
Project description:To further understand the biological properties of hair cells of the mammalian cochlea, we examined the transcriptome of adult inner and outer hair cells. Morphologically distinct inner and outer hair cells were isolated from the organ of Corti from adult CBA/J mice. One thousand inner and outer hair cells were separately collected for each biological replicate, using the suction pipette technique. RNA sequencing of two biological replicates of IHCs and three biological replicates of OHCs, each with two technical repeats, was performed. The resulting sequenced reads were mapped. Comparisons between inner and outer hair cells allow identification of enriched genes, as well as differentially expressed genes that result in cellular specialization. Our dataset provides an extensive resource for understanding the molecular mechanisms underlying morphology, function, and pathology of adult mouse inner and outer hair cells.
Project description:This study investigates how lead exposure triggers cochlear synaptopathy and hearing loss in mice. Young-adult CBA/J mice were given lead acetate in drinking water for 28 days. We assessed hearing thresholds, outer hair cell activity, and synaptic changes in the cochlea. Lead exposure raises hearing thresholds, indicating cochlear synaptopathy. Notably affects synapses in the basal turn without impacting outer hair cells. In addition to this, lead altered the abundance of 352 synaptic proteins, with the synaptic vesicle cycle pathway prominently affected. Lead-induced cochlear synaptopathy targets basal cochlear regions, implicating synaptic vesicle cycle signaling in hearing loss. Revealing specific mechanisms behind lead-induced hearing deficits enhances targeted interventions and preventive strategies, advancing our understanding of lead induced hearing loss.
Project description:Efferent inhibition of cochlear outer hair cells is mediated by nicotinic cholinergic receptors containing alpha9 (a9) and alpha10 subunits. Mice lacking a9 nicotinic subunits fail to exhibit classic olivocochlear responses and are characterized by abnormal synaptic morphology at the base of outer hair cells. To detail molecular changes induced upon the loss of a9 subunit, we sampled cochlear RNA from wild type and a9 null mice at postnatal (P) days spanning periods of synapse formation and maturation (P3, P7, P13 and P60). Our findings point to a delay in cochlear maturation starting at the onset of hearing (P13), as well as an up-regulation of various GABA receptor subunits in adult mice lacking the a9 nicotinic subunit. Cochleae were removed at postnatal ages P3, P7, P13 and P60. Cochlear tissues from 3-5 mice were pooled per replicate; biological triplicates were performed for each age and genotype.
Project description:In order to determine the regulators of outer hair cell postnatal maturation, we utilized the RiboTag mouse model to perform a detailed transcriptomic analysis of outer hair cells at five postnatal developmental time points: P8, P14, P28, 6 weeks (6wk) and 10 weeks (10wk). This analysis resulted in consistent enrichment of outer hair cell expressed genes in the immunoprecipitated RNA compared to whole cochlear input RNA from each time point. Using transcription factor binding motif prediction on a set of defined outer hair cell enriched genes, we further use this dataset to identify the helios transcription factor as a regulator of the postnatal outer hair cell transcriptome.