Inhibition of Histone Methyltransferase G9a Attenuates Noise-Induced Cochlear Synaptopathy and Hearing Loss


Posttranslational modification of histones alters their interaction with DNA and nuclear proteins, influencing gene expression and cell fate. In this study, we investigated the effect of G9a (KMT1C, EHMT2), a major histone lysine methyltransferase encoded by the human EHMT2 gene and responsible for histone H3 lysine 9 dimethylation (H3K9me2) on noise-induced permanent hearing loss (NIHL) in adult CBA/J mice. The conditions of noise exposure used in this study led to losses of cochlear synapses and outer hair cells (OHCs) and permanent auditory threshold shifts. Inhibition of G9a with its specific inhibitor BIX 01294 or with siRNA significantly attenuated these pathological features. Treatment with BIX 01294 also prevented the noise-induced decrease of KCNQ4 immunolabeling in OHCs. Additionally, G9a was increased in cochlear cells, including both outer and inner sensory hair cells, some spiral ganglion neurons (SGNs), and marginal cells, 1 h after the completion of the noise exposure. Also subsequent to noise exposure, immunoreactivity for H3K9me2 appeared in some nuclei of OHCs following a high-to-low frequency gradient with more labeled OHCs in the 45-kHz than the 32-kHz region, as well as in the marginal cells and in some SGNs of the basal turn. These findings suggest that epigenetic modifications of H3K9me2 are involved in NIHL and that pharmacological targeting of G9a may offer a strategy for protection against cochlear synaptopathy and NIHL.

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  1. Chen X, El Gazzar M, Yoza BK, McCall CE (2009) The NF-kappaB factor RelB and histone H3 lysine methyltransferase G9a directly interact to generate epigenetic silencing in endotoxin tolerance. J Biol Chem 284:27857–27865

  2. Chen FQ, Zheng HW, Hill K, Sha SH (2012) Traumatic noise activates Rho-family GTPases through transient cellular energy depletion. J Neurosci 32:12421–12430

  3. Chen J, Hill K, Sha SH (2016) Inhibitors of histone deacetylases attenuate noise-induced hearing loss. J Assoc Res Otolaryngol 17:289–302

  4. Fettiplace R (2017) Hair cell transduction, tuning, and synaptic transmission in the mammalian cochlea. Compr Physiol 7:1197–1227

  5. Han Y, Wang X, Chen J, Sha SH (2015) Noise-induced cochlear F-actin depolymerization is mediated via ROCK2/p-ERM signaling. J Neurochem 133:617–628

  6. Hertzano R, Montcouquiol M, Rashi-Elkeles S, Elkon R, Yucel R, Frankel WN, Rechavi G, Moroy T, Friedman TB, Kelley MW, Avraham KB (2004) Transcription profiling of inner ears from Pou4f3(ddl/ddl) identifies Gfi1 as a target of the Pou4f3 deafness gene. Hum Mol Genet 13:2143–2153

  7. Hill K, Yuan H, Wang X, Sha SH (2016) Noise-induced loss of hair cells and cochlear synaptopathy are mediated by the activation of AMPK. J Neurosci 36:7497–7510

  8. Jaumann M, Dettling J, Gubelt M, Zimmermann U, Gerling A, Paquet-Durand F, Feil S, Wolpert S, Franz C, Varakina K, Xiong H, Brandt N, Kuhn S, Geisler HS, Rohbock K, Ruth P, Schlossmann J, Hutter J, Sandner P, Feil R, Engel J, Knipper M, Ruttiger L (2012) cGMP-Prkg1 signaling and Pde5 inhibition shelter cochlear hair cells and hearing function. Nat Med 18:252–259

  9. Jiang H, Sha SH, Schacht J (2005) NF-kappaB pathway protects cochlear hair cells from aminoglycoside-induced ototoxicity. J Neurosci Res 79:644–651

  10. Kharkovets T, Dedek K, Maier H, Schweizer M, Khimich D, Nouvian R, Vardanyan V, Leuwer R, Moser T, Jentsch TJ (2006) Mice with altered KCNQ4 K+ channels implicate sensory outer hair cells in human progressive deafness. EMBO J 25:642–652

  11. Kouzarides T (2007) Chromatin modifications and their function. Cell 128:693–705

  12. Kubisch C, Schroeder BC, Friedrich T, Lutjohann B, El-Amraoui A, Marlin S, Petit C, Jentsch TJ (1999) KCNQ4, a novel potassium channel expressed in sensory outer hair cells, is mutated in dominant deafness. Cell 96:437–446

  13. Kujawa SG, Liberman MC (2006) Acceleration of age-related hearing loss by early noise exposure: evidence of a misspent youth. J Neurosci 26:2115–2123

  14. Lang H, Schulte BA, Zhou D, Smythe N, Spicer SS, Schmiedt RA (2006) Nuclear factor kappaB deficiency is associated with auditory nerve degeneration and increased noise-induced hearing loss. J Neurosci 26:3541–3550

  15. Laumet G, Garriga J, Chen SR, Zhang Y, Li DP, Smith TM, Dong Y, Jelinek J, Cesaroni M, Issa JP, Pan HL (2015) G9a is essential for epigenetic silencing of K(+) channel genes in acute-to-chronic pain transition. Nat Neurosci 18:1746–1755

  16. Malmquist NA, Moss TA, Mecheri S, Scherf A, Fuchter MJ (2012) Small-molecule histone methyltransferase inhibitors display rapid antimalarial activity against all blood stage forms in Plasmodium falciparum. Proc Natl Acad Sci U S A 109:16708–16713

  17. Muller M, von Hunerbein K, Hoidis S, Smolders JW (2005) A physiological place-frequency map of the cochlea in the CBA/J mouse. Hear Res 202:63–73

  18. Nie L (2008) KCNQ4 mutations associated with nonsyndromic progressive sensorineural hearing loss. Curr Opin Otolaryngol Head Neck Surg 16:441–444

  19. Ohlemiller KK, Kaur T, Warchol ME, Withnell RH (2018) The endocochlear potential as an indicator of reticular lamina integrity after noise exposure in mice. Hear Res 361:138–151

  20. Oishi N, Chen FQ, Zheng HW, Sha SH (2013) Intra-tympanic delivery of short interfering RNA into the adult mouse cochlea. Hear Res 296:36–41

  21. Pawelczyk M, Van Laer L, Fransen E, Rajkowska E, Konings A, Carlsson PI, Borg E, Van Camp G, Sliwinska-Kowalska M (2009) Analysis of gene polymorphisms associated with K ion circulation in the inner ear of patients susceptible and resistant to noise-induced hearing loss. Ann Hum Genet 73:411–421

  22. Salzberg AC, Harris-Becker A, Popova EY, Keasey N, Loughran TP, Claxton DF, Grigoryev SA (2017) Genome-wide mapping of histone H3K9me2 in acute myeloid leukemia reveals large chromosomal domains associated with massive gene silencing and sites of genome instability. PLoS One 12:e0173723

  23. Scheer S, Zaph C (2017) The lysine methyltransferase G9a in immune cell differentiation and function. Front Immunol 8:429

  24. Sha SH, Schacht J (2017) Emerging therapeutic interventions against noise-induced hearing loss. Expert Opin Investig Drugs 26:85–96

  25. Shinkai Y, Tachibana M (2011) H3K9 methyltransferase G9a and the related molecule GLP. Genes Dev 25:781–788

  26. Tachibana M, Sugimoto K, Nozaki M, Ueda J, Ohta T, Ohki M, Fukuda M, Takeda N, Niida H, Kato H, Shinkai Y (2002) G9a histone methyltransferase plays a dominant role in euchromatic histone H3 lysine 9 methylation and is essential for early embryogenesis. Genes Dev 16:1779–1791

  27. Taylor CR, Levenson RM (2006) Quantification of immunohistochemistry—issues concerning methods, utility and semiquantitative assessment II. Histopathology 49:411–424

  28. Viberg A, Canlon B (2004) The guide to plotting a cochleogram. Hear Res 197:1–10

  29. Walker RA (2006) Quantification of immunohistochemistry—issues concerning methods, utility and semiquantitative assessment I. Histopathology 49:406–410

  30. Wallis D, Hamblen M, Zhou Y, Venken KJ, Schumacher A, Grimes HL, Zoghbi HY, Orkin SH, Bellen HJ (2003) The zinc finger transcription factor Gfi1, implicated in lymphomagenesis, is required for inner ear hair cell differentiation and survival. Development 130:221–232

  31. Wan G, Gomez-Casati ME, Gigliello AR, Liberman MC, Corfas G (2014) Neurotrophin-3 regulates ribbon synapse density in the cochlea and induces synapse regeneration after acoustic trauma. eLife 3

  32. Wang Y, Hirose K, Liberman MC (2002) Dynamics of noise-induced cellular injury and repair in the mouse cochlea. J Assoc Res Otolaryngol 3:248–268

  33. Yokochi T, Poduch K, Ryba T, Lu J, Hiratani I, Tachibana M, Shinkai Y, Gilbert DM (2009) G9a selectively represses a class of late-replicating genes at the nuclear periphery. Proc Natl Acad Sci U S A 106:19363–19368

  34. Yu H, Lin Q, Wang Y, He Y, Fu S, Jiang H, Yu Y, Sun S, Chen Y, Shou J, Li H (2013) Inhibition of H3K9 methyltransferases G9a/GLP prevents ototoxicity and ongoing hair cell death. Cell Death Dis 4:e506

  35. Yuan H, Wang X, Hill K, Chen J, Lemasters J, Yang SM, Sha SH (2015) Autophagy attenuates noise-induced hearing loss by reducing oxidative stress. Antioxid Redox Signal 22:1308–1324

  36. Zheng HW, Chen J, Sha SH (2014) Receptor-interacting protein kinases modulate noise-induced sensory hair cell death. Cell Death Dis 5:e1262

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The research project described was supported by grant R01 DC009222 from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health. This work was conducted in the WR Building at MUSC in renovated space supported by grant C06 RR014516. Animals were housed in MUSC CRI animal facilities supported by grant C06 RR015455 from the Extramural Research Facilities Program of the National Center for Research Resources. We thank Dr. Jochen Schacht for his valuable comments on the manuscript. We also thank Dr. Yuan Shao in the MUSC Biorepository & Tissue Analysis Shared Resource for technical assistance with cochlear paraffin sections and Andra Talaska for proofreading of the manuscript.

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Correspondence to Su-Hua Sha.

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Xiong, H., Long, H., Pan, S. et al. Inhibition of Histone Methyltransferase G9a Attenuates Noise-Induced Cochlear Synaptopathy and Hearing Loss. JARO 20, 217–232 (2019).

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  • noise-induced hair cell loss
  • lysine methyltransferase G9a
  • epigenetic modification
  • cochlear synapses
  • protection of noise-induced hearing loss