Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of mouse with unilateral cochlear removal in Cochlear Nucleus at P7 and P21

ABSTRACT: Deprivation of peripheral nerve input by cochlear removal in young mice results in dramatic neuron death in the cochlear nucleus (CN). The same manipulation in older mice does not result in significant loss. The molecular basis of this critical period of vulnerability remains largely unknown. Here we identified genes regulated at early time points after cochlear removal at ages when neurons are vulnerable (postnatal day (P)7) or invulnerable (P21) to this challenge. Afferent deprivation regulated very different sets of genes at P7 and P21. These genes showed a variety of functions at both ages, but surprisingly there was no net increase in pro-apoptotic genes at P7. A large set of upregulated immune-related genes was identified at P21. Experiment Overall Design: Mice received unilateral cochlear removals. At 6, 12, 24, and 48 hours after surgery, the CN ipsilateral and contralateral were removed, and RNA isolated from separate pools of tissue for each replicate. Deafferented CN were compared to age-matched and time-matched contralateral, control CN to identify genes regulated by cochlear removal at age P7 and P21.

ORGANISM(S): Mus musculus

SUBMITTER: Julie Harris

PROVIDER: E-GEOD-5394 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Spiral ganglion neurons (SGNs) and the associated components of the auditory nerve are primary carriers of auditory information from hair cells to the brain. Loss of SGNs occurs with many pathological conditions, resulting in permanent sensorineural hearing loss. Neural stem/progenitors (NSPs) have been well-characterized in several locations of adult brain and retina. However, it is unclear whether NSPs are present in the adult auditory nerve. Here we examined the self-renewal potential of the adult auditory nerve using ouabain application as a well-established mouse model of acute SGN injury. The observed increase in cell proliferation, alteration in enchromatin/heterochromatin ratio and down-regulation of histone deacetylase expression in glial cells suggest that the quiescent glial cells convert to an activated state after SGN degeneration. This was further confirmed by global gene expression analysis of injured auditory nerves, which showed up-regulation of numerous neurogenesis- and/or development-associated genes shortly after ouabain exposure. These genes include molecular markers commonly used for the identification of NSPs. Under a strict culture regimen, auditory nerve-derived cells of adult mouse ears gave rise to neurospheres, suggesting that multipotent NSPs are present in adult cochlear nerve. Neurosphere assays on Sox2 transgenic mice revealed that Sox2+ glial cells are the source for NSPs. Our data also showed that acute injury or hypoxia enhances neurosphere formation. Taken together, our study revealed that glial cells of adult cochlea exhibit several NSP characteristics, and hence these mature non-neuronal cells may be important targets for promoting self-repair of degenerative auditory nerves. Adult Mice (CBA/CaJ, aged 8 to 12 weeks) were anesthetized and subjected to survival surgery to expose the bulla of the right ear. A ouabain solution (3 mM, approximately 10 ul) was administered in the round window niche. This solution was wicked away and replaced with fresh ouabain approximately every 10 min during a cummulative exposure period of 60 min. The left ears (i.e., contralateral) were not surgically manipulated and were used as controls. Mice were maintained for 3 days or 7 days following treatments, then euthanized, and the oubain-treated and contralateral cochleas were removed. Cochleas underwent microdissection to remove the outer bony cochlear shell and cochlear lateral wall, thus preserving the modiolus portion of cochlea which contains mainly the auditory nerve. All sample types were prepared in experimental triplicate (n=3).

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.

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Transcription profiling of mouse with unilateral cochlear removal in Cochlear Nucleus at P7 and P21

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