Expression pattern of cochlear microRNAs in the mammalian auditory hindbrain

Constanze Krohs,Naama Messika-Gold,Hans Gerd Nothwang,Mor Bordeynik-Cohen,Ran Elkon,Karen B Avraham

doi:10.1007/s00441-020-03290-x

Abstract

The auditory system comprises the auditory periphery, engaged in sound transduction and the central auditory system, implicated in auditory information processing and perception. Recently, evidence mounted that the mammalian peripheral and central auditory systems share a number of genes critical for proper development and function. This bears implication for auditory rehabilitation and evolution of the auditory system. To analyze to which extent microRNAs (miRNAs) belong to genes shared between both systems, we characterize the expression pattern of 12 cochlea-abundant miRNAs in the central auditory system. Quantitative real-time PCR (qRT-PCR) demonstrated expression of all 12 genes in the cochlea, the auditory hindbrain and the non-auditory prefrontal cortex (PFC) at embryonic stage (E)16 and postnatal stages (P)0 and P30. Eleven of them showed differences in expression between tissues and nine between the developmental time points. Hierarchical cluster analysis revealed that the temporal expression pattern in the auditory hindbrain was more similar to the PFC than to the cochlea. Spatiotemporal expression analysis by RNA in situ hybridization demonstrated widespread expression throughout the cochlear nucleus complex (CNC) and the superior olivary complex (SOC) during postnatal development. Altogether, our data indicate that miRNAs represent a relevant class of genetic factors functioning across the auditory system. Given the importance of gene regulatory network (GRN) components for development, physiology and evolution, the 12 miRNAs provide promising entry points to gain insights into their molecular underpinnings in the auditory system.

Highlights

Hearing requires transduction of weak sound pressure waves in the cochlea and subsequent complex processing of precisely timed electric signals in central auditory structures
In a first set of experiments, we performed Quantitative real-time PCR (qRT-PCR) to study the expression of the mature forms in more detail during development in both the cochlea and the superior olivary complex (SOC), a prominent composite auditory hindbrain structure
As miRNAs play an important role during development, we chose the E16, P0 time points that cover embryonic and perinatal stages characterized by ongoing highly dynamic developmental processes and P30, a time point when the auditory system is fully functional

Summary

Introduction

Hearing requires transduction of weak sound pressure waves in the cochlea and subsequent complex processing of precisely timed electric signals in central auditory structures. Anatomical, developmental and physiological studies led to the conclusion that both the coiled cochlea and the complex composition of the auditory hindbrain represent mammalian-specific traits of the vertebrate auditory system (Carr and Soares 2002; Nothwang 2016; Manley and Clack 2004; Manley 2012) Despite their disparate functions and unique specializations, the cochlea and the auditory hindbrain share critical genes for proper development and function (Michalski and Petit 2019; Nothwang et al 2015; Willaredt et al 2014). Mutations in miR-96 affect the development of both the hair cells in the cochlea (Lewis et al 2009; Mencia et al 2009) and circuits in the auditory hindbrain (Schlüter et al 2018) and the essential hair bundle proteins cdhr and cdhr are required for proper integration of GABAergic interneurons in the auditory cortex (Libé-Philippot et al 2017)

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Conclusion