A cardinal feature of the auditory pathway is frequency selectivity, represented in a tonotopic map from the cochlea to the cortex. The molecular determinants of the auditory frequency map are unknown. Here, we discovered that the transcription factor ISL1 regulates the molecular and cellular features of auditory neurons, including the formation of the spiral ganglion and peripheral and central processes that shape the tonotopic representation of the auditory map. We selectively knocked out Isl1 in auditory neurons using Neurod1Cre strategies. In the absence of Isl1, spiral ganglion neurons migrate into the central cochlea and beyond, and the cochlear wiring is profoundly reduced and disrupted. The central axons of Isl1 mutants lose their topographic projections and segregation at the cochlear nucleus. Transcriptome analysis of spiral ganglion neurons shows that Isl1 regulates neurogenesis, axonogenesis, migration, neurotransmission-related machinery, and synaptic communication patterns. We show that peripheral disorganization in the cochlea affects the physiological properties of hearing in the midbrain and auditory behavior. Surprisingly, auditory processing features are preserved despite the significant hearing impairment, revealing central auditory pathway resilience and plasticity in Isl1 mutant mice. Mutant mice have a reduced acoustic startle reflex, altered prepulse inhibition, and characteristics of compensatory neural hyperactivity centrally. Our findings show that ISL1 is one of the obligatory factors required to sculpt auditory structural and functional tonotopic maps. Still, upon Isl1 deletion, the ensuing central plasticity of the auditory pathway does not suffice to overcome developmentally induced peripheral dysfunction of the cochlea.

Department of Auditory Neuroscience Institute of Experimental Medicine Czech Academy of Sciences 14220 Prague Czechia

Department of Biology University of Iowa Iowa City IA 52242 1324

Department of Otolaryngology University of Iowa Iowa City IA 52242 1324

Department of Physiology School of Medicine University of Nevada Reno NV 89557

Laboratory of Gene Expression Institute of Biotechnology Czech Academy of Sciences 25250 Vestec Czechia

Laboratory of Light Microscopy Institute of Molecular Genetics Czech Academy of Sciences 14220 Prague Czechia

Laboratory of Molecular Pathogenetics Institute of Biotechnology Czech Academy of Sciences 25250 Vestec Czechia

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Muniak M. A., et al. , “Central projections of spiral ganglion neurons” in The Primary Auditory Neurons of the Mammalian Cochlea, Dabdoub A., Fritzsch B., Popper A. N., Fay R. R., Eds. (Springer, New York, NY, 2016) pp. 157–190.

Rubel E. W., Fritzsch B., Auditory system development: Primary auditory neurons and their targets. Annu. Rev. Neurosci. 25, 51–101 (2002). PubMed

Shrestha B. R., et al. , Sensory neuron diversity in the inner ear is shaped by activity. Cell 174, 1229–1246.e17 (2018). PubMed PMC

Petitpré C., et al. , Neuronal heterogeneity and stereotyped connectivity in the auditory afferent system. Nat. Commun. 9, 3691 (2018). PubMed PMC

Sun S., et al. , Hair cell mechanotransduction regulates spontaneous activity and spiral ganglion subtype specification in the auditory system. Cell 174, 1247–1263.e15 (2018). PubMed PMC

Petitpre C., et al. , Single-cell RNA-sequencing analysis of the developing mouse inner ear identifies molecular logic of auditory neuron diversification. Nat. Commun. 13, 3878 (2022). PubMed PMC

Kandler K., Clause A., Noh J., Tonotopic reorganization of developing auditory brainstem circuits. Nat. Neurosci. 12, 711–717 (2009). PubMed PMC

Di Bonito M., Studer M., Cellular and molecular underpinnings of neuronal assembly in the central auditory system during mouse development. Front. Neural Circuits 11, 18 (2017). PubMed PMC

Lopez-Poveda E. A., Olivocochlear efferents in animals and humans: From anatomy to clinical relevance. Front. Neurol. 9, 197 (2018). PubMed PMC

Fritzsch B., Elliott K. L., Evolution and development of the inner ear efferent system: Transforming a motor neuron population to connect to the most unusual motor protein via ancient nicotinic receptors. Front. Cell. Neurosci. 11, 114 (2017). PubMed PMC

Ma Q., Anderson D. J., Fritzsch B., Neurogenin 1 null mutant ears develop fewer, morphologically normal hair cells in smaller sensory epithelia devoid of innervation. J. Assoc. Res. Otolaryngol. 1, 129–143 (2000). PubMed PMC

Kim W.-Y., et al. , NeuroD-null mice are deaf due to a severe loss of the inner ear sensory neurons during development. Development 128, 417–426 (2001). PubMed PMC

Duncan J. S., Fritzsch B., Continued expression of GATA3 is necessary for cochlear neurosensory development. PLoS One 8, e62046 (2013). PubMed PMC

Appler J. M., et al. , Gata3 is a critical regulator of cochlear wiring. J. Neurosci. 33, 3679–3691 (2013). PubMed PMC

Huang E. J., et al. , Brn3a is a transcriptional regulator of soma size, target field innervation and axon pathfinding of inner ear sensory neurons. Development 128, 2421–2432 (2001). PubMed PMC

Liu M., et al. , Essential role of BETA2/NeuroD1 in development of the vestibular and auditory systems. Genes Dev. 14, 2839–2854 (2000). PubMed PMC

Jahan I., Kersigo J., Pan N., Fritzsch B., Neurod1 regulates survival and formation of connections in mouse ear and brain. Cell Tissue Res. 341, 95–110 (2010). PubMed PMC

Filova I., et al. , Early deletion of Neurod1 alters neuronal lineage potential and diminishes neurogenesis in the inner ear. Front. Cell Dev. Biol. 10, 845461 (2022). PubMed PMC

Filova I., et al. , Combined Atoh1 and Neurod1 deletion reveals autonomous growth of auditory nerve fibers. Mol. Neurobiol. 57, 5307–5323 (2020). PubMed PMC

Macova I., et al. , Neurod1 is essential for the primary tonotopic organization and related auditory information processing in the midbrain. J. Neurosci. 39, 984–1004 (2019). PubMed PMC

Dvorakova M., et al. , Incomplete and delayed Sox2 deletion defines residual ear neurosensory development and maintenance. Sci. Rep. 6, 38253 (2016). PubMed PMC

Radde-Gallwitz K., et al. , Expression of Islet1 marks the sensory and neuronal lineages in the mammalian inner ear. J. Comp. Neurol. 477, 412–421 (2004). PubMed PMC

Li H. J., Kapoor A., Giel-Moloney M., Rindi G., Leiter A. B., Notch signaling differentially regulates the cell fate of early endocrine precursor cells and their maturing descendants in the mouse pancreas and intestine. Dev. Biol. 371, 156–169 (2012). PubMed PMC

Sun Y., et al. , A central role for Islet1 in sensory neuron development linking sensory and spinal gene regulatory programs. Nat. Neurosci. 11, 1283–1293 (2008). PubMed PMC

Jahan I., Pan N., Kersigo J., Fritzsch B., Neurod1 suppresses hair cell differentiation in ear ganglia and regulates hair cell subtype development in the cochlea. PLoS One 5, e11661 (2010). PubMed PMC

Li C., et al. , Comprehensive transcriptome analysis of cochlear spiral ganglion neurons at multiple ages. eLife 9, e50491 (2020). PubMed PMC

Stoeckli E. T., Understanding axon guidance: Are we nearly there yet? Development 145, dev151415 (2018). PubMed

Fritzsch B., Kersigo J., Yang T., Jahan I., Pan N., “Neurotrophic factor function during ear development: Expression changes define critical phases for neuronal viability” in The Primary Auditory Neurons of the Mammalian Cochlea, Dabdoub A., Fritzsch B., Popper A. N., Fay R. R., Eds. (Springer, New York, NY, 2016) pp. 49–84.

Dennis D. J., Han S., Schuurmans C., bHLH transcription factors in neural development, disease, and reprogramming. Brain Res. 1705, 48–65 (2019). PubMed

Yang T., Kersigo J., Wu S., Fritzsch B., Bassuk A. G., Prickle1 regulates neurite outgrowth of apical spiral ganglion neurons but not hair cell polarity in the murine cochlea. PLoS One 12, e0183773 (2017). PubMed PMC

Bok J., Zenczak C., Hwang C. H., Wu D. K., Auditory ganglion source of Sonic hedgehog regulates timing of cell cycle exit and differentiation of mammalian cochlear hair cells. Proc. Natl. Acad. Sci. U.S.A. 110, 13869–13874 (2013). PubMed PMC

Pauley S., et al. , Expression and function of FGF10 in mammalian inner ear development. Dev. Dyn. 227, 203–215 (2003). PubMed PMC

Yu Y., et al. , Sensorineural hearing loss and mitochondrial apoptosis of cochlear spiral ganglion neurons in fibroblast growth factor 13 knockout mice. Front. Cell. Neurosci. 15, 658586 (2021). PubMed PMC

Defourny J., et al. , Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells. Nat. Commun. 4, 1438 (2013). PubMed

Coate T. M., et al. , Otic mesenchyme cells regulate spiral ganglion axon fasciculation through a Pou3f4/EphA4 signaling pathway. Neuron 73, 49–63 (2012). PubMed PMC

Fritzsch B., Barbacid M., Silos-Santiago I., The combined effects of trkB and trkC mutations on the innervation of the inner ear. Int. J. Dev. Neurosci. 16, 493–505 (1998). PubMed

Brors D., et al. , Spiral ganglion outgrowth and hearing development in p75-deficient mice. Audiol. Neurotol. 13, 388–395 (2008). PubMed

Coate T. M., Spita N. A., Zhang K. D., Isgrig K. T., Kelley M. W., Neuropilin-2/Semaphorin-3F-mediated repulsion promotes inner hair cell innervation by spiral ganglion neurons. eLife 4, e07830 (2015). PubMed PMC

Wang S. Z., et al. , Slit/Robo signaling mediates spatial positioning of spiral ganglion neurons during development of cochlear innervation. J. Neurosci. 33, 12242–12254 (2013). PubMed PMC

Kim Y. J., et al. , Dcc mediates functional assembly of peripheral auditory circuits. Sci. Rep. 6, 23799 (2016). PubMed PMC

Müller M., von Hünerbein K., Hoidis S., Smolders J. W., A physiological place-frequency map of the cochlea in the CBA/J mouse. Hear. Res. 202, 63–73 (2005). PubMed

Zhou X., Jen P. H., Seburn K. L., Frankel W. N., Zheng Q. Y., Auditory brainstem responses in 10 inbred strains of mice. Brain Res. 1091, 16–26 (2006). PubMed PMC

Chumak T., et al. , BDNF in lower brain parts modifies auditory fiber activity to gain fidelity but increases the risk for generation of central noise after injury. Mol. Neurobiol. 53, 5607–5627 (2016). PubMed PMC

Land R., Burghard A., Kral A., The contribution of inferior colliculus activity to the auditory brainstem response (ABR) in mice. Hear. Res. 341, 109–118 (2016). PubMed

Wolter S., et al. , GC-B deficient mice with axon bifurcation loss exhibit compromised auditory processing. Front. Neural Circuits 12, 65 (2018). PubMed PMC

Chambers A. R., et al. , Central gain restores auditory processing following near-complete cochlear denervation. Neuron 89, 867–879 (2016). PubMed PMC

Harris J. A., Rubel E. W., Afferent regulation of neuron number in the cochlear nucleus: Cellular and molecular analyses of a critical period. Hear. Res. 216–217, 127–137 (2006). PubMed

Lauer A. M., Connelly C. J., Graham H., Ryugo D. K., Morphological characterization of bushy cells and their inputs in the laboratory mouse (Mus musculus) anteroventral cochlear nucleus. PLoS One 8, e73308 (2013). PubMed PMC

Karmakar K., et al. , Hox2 genes are required for tonotopic map precision and sound discrimination in the mouse auditory brainstem. Cell Rep. 18, 185–197 (2017). PubMed

Fujiyama T., et al. , Inhibitory and excitatory subtypes of cochlear nucleus neurons are defined by distinct bHLH transcription factors, Ptf1a and Atoh1. Development 136, 2049–2058 (2009). PubMed

Gruters K. G., Groh J. M., Sounds and beyond: Multisensory and other non-auditory signals in the inferior colliculus. Front. Neural Circuits 6, 96 (2012). PubMed PMC

Yeomans J. S., Frankland P. W., The acoustic startle reflex: Neurons and connections. Brain Res. Brain Res. Rev. 21, 301–314 (1995). PubMed

Koch M., The neurobiology of startle. Prog. Neurobiol. 59, 107–128 (1999). PubMed

Swerdlow N. R., Geyer M. A., Braff D. L., Neural circuit regulation of prepulse inhibition of startle in the rat: Current knowledge and future challenges. Psychopharmacology (Berl.) 156, 194–215 (2001). PubMed

Fitch R. H., Threlkeld S. W., McClure M. M., Peiffer A. M., Use of a modified prepulse inhibition paradigm to assess complex auditory discrimination in rodents. Brain Res. Bull. 76, 1–7 (2008). PubMed PMC

Hickox A. E., Liberman M. C., Is noise-induced cochlear neuropathy key to the generation of hyperacusis or tinnitus? J. Neurophysiol. 111, 552–564 (2014). PubMed PMC

Pfaff S. L., Mendelsohn M., Stewart C. L., Edlund T., Jessell T. M., Requirement for LIM homeobox gene Isl1 in motor neuron generation reveals a motor neuron-dependent step in interneuron differentiation. Cell 84, 309–320 (1996). PubMed

Yang L., et al. , Isl1Cre reveals a common Bmp pathway in heart and limb development. Development 133, 1575–1585 (2006). PubMed PMC

Huber K., et al. , The LIM-Homeodomain transcription factor Islet-1 is required for the development of sympathetic neurons and adrenal chromaffin cells. Dev. Biol. 380, 286–298 (2013). PubMed PMC

Ahlgren U., Pfaff S. L., Jessell T. M., Edlund T., Edlund H., Independent requirement for ISL1 in formation of pancreatic mesenchyme and islet cells. Nature 385, 257–260 (1997). PubMed

Cai C. L., et al. , Isl1 identifies a cardiac progenitor population that proliferates prior to differentiation and contributes a majority of cells to the heart. Dev. Cell 5, 877–889 (2003). PubMed PMC

Liang X., et al. , Isl1 is required for multiple aspects of motor neuron development. Mol. Cell. Neurosci. 47, 215–222 (2011). PubMed PMC

Kania A., Jessell T. M., Topographic motor projections in the limb imposed by LIM homeodomain protein regulation of ephrin-A:EphA interactions. Neuron 38, 581–596 (2003). PubMed

Chumak T., et al. , Deterioration of the medial olivocochlear efferent system accelerates age-related hearing loss in Pax2-Isl1 transgenic mice. Mol. Neurobiol. 53, 2368–2383 (2016). PubMed

Bohuslavova R., et al. , Pax2-Islet1 transgenic mice are hyperactive and have altered cerebellar foliation. Mol. Neurobiol. 54, 1352–1368 (2017). PubMed PMC

Huang M., Kantardzhieva A., Scheffer D., Liberman M. C., Chen Z. Y., Hair cell overexpression of Islet1 reduces age-related and noise-induced hearing loss. J. Neurosci. 33, 15086–15094 (2013). PubMed PMC

Chumak T., et al. , Overexpression of Isl1 under the Pax2 promoter, leads to impaired sound processing and increased inhibition in the inferior colliculus. Int. J. Mol. Sci. 22, 4507 (2021). PubMed PMC

Morris J. K., et al. , A disorganized innervation of the inner ear persists in the absence of ErbB2. Brain Res. 1091, 186–199 (2006). PubMed PMC

Mao Y., Reiprich S., Wegner M., Fritzsch B., Targeted deletion of Sox10 by Wnt1-cre defects neuronal migration and projection in the mouse inner ear. PLoS One 9, e94580 (2014). PubMed PMC

Geyer M. A., McIlwain K. L., Paylor R., Mouse genetic models for prepulse inhibition: An early review. Mol. Psychiatry 7, 1039–1053 (2002). PubMed

LeMasurier M., Gillespie P. G., Hair-cell mechanotransduction and cochlear amplification. Neuron 48, 403–415 (2005). PubMed

Dallos P., et al. , Prestin-based outer hair cell motility is necessary for mammalian cochlear amplification. Neuron 58, 333–339 (2008). PubMed PMC

Herranen A., et al. , Deficiency of the ER-stress-regulator MANF triggers progressive outer hair cell death and hearing loss. Cell Death Dis. 11, 100 (2020). PubMed PMC

Liberman L. D., Liberman M. C., Cochlear efferent innervation is sparse in humans and decreases with age. J. Neurosci. 39, 9560–9569 (2019). PubMed PMC

Hafidi A., Peripherin-like immunoreactivity in type II spiral ganglion cell body and projections. Brain Res. 805, 181–190 (1998). PubMed

Elliott K. L., et al. , Developmental changes in Peripherin-eGFP expression in spiral ganglion neurons. Front. Cell. Neurosci. 15, 678113 (2021). PubMed PMC

Zhang K. D., Coate T. M., Recent advances in the development and function of type II spiral ganglion neurons in the mammalian inner ear. Semin. Cell Dev. Biol. 65, 80–87 (2017). PubMed PMC

Froud K. E., et al. , Type II spiral ganglion afferent neurons drive medial olivocochlear reflex suppression of the cochlear amplifier. Nat. Commun. 6, 7115 (2015). PubMed PMC

Maison S., Liberman L. D., Liberman M. C., Type II cochlear ganglion neurons do not drive the olivocochlear reflex: Re-examination of the cochlear phenotype in peripherin knock-out mice. eNeuro 3, ENEURO.0207-16.2016 (2016). PubMed PMC

Matei V., et al. , Smaller inner ear sensory epithelia in Neurog 1 null mice are related to earlier hair cell cycle exit. Dev. Dyn. 234, 633–650 (2005). PubMed PMC

Pauley S., Lai E., Fritzsch B., Foxg1 is required for morphogenesis and histogenesis of the mammalian inner ear. Dev. Dyn. 235, 2470–2482 (2006). PubMed PMC

Nichols D. H., et al. , Lmx1a is required for segregation of sensory epithelia and normal ear histogenesis and morphogenesis. Cell Tissue Res. 334, 339–358 (2008). PubMed PMC

Pavlinkova G., Molecular aspects of the development and function of auditory neurons. Int. J. Mol. Sci. 22, 131 (2020). PubMed PMC

Zine A., Messat Y., Fritzsch B., A human induced pluripotent stem cell-based modular platform to challenge sensorineural hearing loss. Stem Cells 39, 697–706 (2021). PubMed PMC

National Research Council, Guide for the Care and Use of Laboratory Animals (National Academies Press, Washington, DC, 1996). PubMed

Filova I., et al. , ISL1 is necessary for auditory neuron development and contributes toward tonotopic organization. NCBI Gene Expression Omnibus. https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE182575. Deposited 23 August 2021. PubMed PMC

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