The Role of the RNA-Editor Adarb1 in Peripheral Auditory Function - Project Summary/Abstract The inner ear is a specialized sensory system that encodes auditory and vestibular information through precise regulation of synaptic transmission and neural connectivity. Disorders such as sensorineural hearing loss, inner ear trauma, vertigo, and tinnitus affect billions worldwide, yet the molecular mechanisms underlying auditory and vestibular development and function remain poorly understood. Elucidating these pathways is essential for advancing knowledge and developing effective therapies for inner ear disorders. The majority of current research focuses on gene expression, leaving critical gaps in processes such as alternative splicing, protein modification, and RNA editing. RNA editing, a critical post-transcriptional modification, plays vital roles across biological systems, including the CNS, where its disruption can result in severe phenotypes such as intractable seizures and postnatal lethality in mice. However, the role of RNA editing in the inner ear remains completely unexplored, representing a significant gap in our understanding. ADARB1, an RNA editing enzyme, catalyzes the deamination of adenosine to inosine in Gria2 mRNA, rendering the GLUA2 receptor calcium-impermeable and supporting normal auditory processing. Our preliminary studies, together with published RNA sequencing, immunofluorescence, and RNAscope data, demonstrate robust ADARB1 expression in spiral ganglion neurons (SGNs). Nevertheless, the cellular and molecular functions of ADARB1 in the auditory system are completely unknown. In this proposal, we hypothesize that ADARB1 is essential for auditory function and exhibits cell-type-specific variability in RNA editing, splicing, and isoform expression that affects the development, differentiation, and function of spiral ganglion neurons. Specifically, we propose to conditionally delete ADARB1 from SGNs and show that its conditional deletion leads to structural and functional deficits in these populations. To test these hypotheses, we will: (1) define the developmental and cell-type-specific landscape of ADARB1 expression and RNA editing in the inner ear using a novel in situ approach, (2) generate a novel Adarb1 conditional knockout line by crossing our Adarb1-floxed mice with NeflCre mice; (3) assess disrupted 8thCN function using auditory brainstem responses (ABRs), and preserved hair cell and strial functions with distortion product otoacoustic emissions (DPOAEs), and SGN differentiation, survival, and innervation of hair cells using histological analysis; Collectively, this research will provide foundational insights into ADARB1-mediated RNA editing in the inner ear, elucidating genetic mechanisms underlying auditory function and informing future therapeutic strategies for hearing and balance disorders.
