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Bryant D, Pauzuolyte V, Ingham NJ, Patel A, Pagarkar W, Anderson LA, Smith KE, Moulding DA, Leong YC, Jafree DJ, Long DA, Al-Yassin A, Steel KP, Jagger DJ, Forge A, Berger W, Sowden JC, Bitner-Glindzicz M. The timing of auditory sensory deficits in Norrie disease has implications for therapeutic intervention. JCI Insight 2022; 7:148586. [PMID: 35132964 PMCID: PMC8855802 DOI: 10.1172/jci.insight.148586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 12/10/2021] [Indexed: 11/29/2022] Open
Abstract
Norrie disease is caused by mutation of the NDP gene, presenting as congenital blindness followed by later onset of hearing loss. Protecting patients from hearing loss is critical for maintaining their quality of life. This study aimed to understand the onset of pathology in cochlear structure and function. By investigating patients and juvenile Ndp-mutant mice, we elucidated the sequence of onset of physiological changes (in auditory brainstem responses, distortion product otoacoustic emissions, endocochlear potential, blood-labyrinth barrier integrity) and determined the cellular, histological, and ultrastructural events leading to hearing loss. We found that cochlear vascular pathology occurs earlier than previously reported and precedes sensorineural hearing loss. The work defines a disease mechanism whereby early malformation of the cochlear microvasculature precedes loss of vessel integrity and decline of endocochlear potential, leading to hearing loss and hair cell death while sparing spiral ganglion cells. This provides essential information on events defining the optimal therapeutic window and indicates that early intervention is needed. In an era of advancing gene therapy and small-molecule technologies, this study establishes Ndp-mutant mice as a platform to test such interventions and has important implications for understanding the progression of hearing loss in Norrie disease.
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Affiliation(s)
- Dale Bryant
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Valda Pauzuolyte
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Neil J Ingham
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Aara Patel
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Waheeda Pagarkar
- Great Ormond Street Hospital, Great Ormond Street, London, United Kingdom
| | - Lucy A Anderson
- UCL Ear Institute, University College London, London, United Kingdom
| | - Katie E Smith
- UCL Ear Institute, University College London, London, United Kingdom
| | - Dale A Moulding
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Yeh C Leong
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Daniyal J Jafree
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom.,UCL MB/PhD Programme, Faculty of Medical Sciences, University College London, London, United Kingdom
| | - David A Long
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Amina Al-Yassin
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Karen P Steel
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Daniel J Jagger
- UCL Ear Institute, University College London, London, United Kingdom
| | - Andrew Forge
- UCL Ear Institute, University College London, London, United Kingdom
| | - Wolfgang Berger
- Institute of Medical Molecular Genetics, University of Zürich, Schlieren, Switzerland.,Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Jane C Sowden
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
| | - Maria Bitner-Glindzicz
- UCL Great Ormond Street Institute of Child Health, University College London, and NIHR Great Ormond Street Hospital Biomedical Research Centre, London, United Kingdom
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Functional P2X 7 Receptors in the Auditory Nerve of Hearing Rodents Localize Exclusively to Peripheral Glia. J Neurosci 2021; 41:2615-2629. [PMID: 33563723 DOI: 10.1523/jneurosci.2240-20.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 12/03/2020] [Accepted: 01/09/2021] [Indexed: 11/21/2022] Open
Abstract
P2X7 receptors (P2X7Rs) are associated with numerous pathophysiological mechanisms, and this promotes them as therapeutic targets for certain neurodegenerative conditions. However, the identity of P2X7R-expressing cells in the nervous system remains contentious. Here, we examined P2X7R functionality in auditory nerve cells from rodents of either sex, and determined their functional and anatomic expression pattern. In whole-cell recordings from rat spiral ganglion cultures, the purinergic agonist 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) activated desensitizing currents in spiral ganglion neurons (SGNs) but non-desensitizing currents in glia that were blocked by P2X7R-specific antagonists. In imaging experiments, BzATP gated sustained Ca2+ entry into glial cells. BzATP-gated uptake of the fluorescent dye YO-PRO-1 was reduced and slowed by P2X7R-specific antagonists. In rats, P2X7Rs were immuno-localized predominantly within satellite glial cells (SGCs) and Schwann cells (SCs). P2X7R expression was not detected in the portion of the auditory nerve within the central nervous system. Mouse models allowed further exploration of the distribution of cochlear P2X7Rs. In GENSAT reporter mice, EGFP expression driven via the P2rx7 promoter was evident in SGCs and SCs but was undetectable in SGNs. A second transgenic model showed a comparable cellular distribution of EGFP-tagged P2X7Rs. In wild-type mice the discrete glial expression was confirmed using a P2X7-specific nanobody construct. Our study shows that P2X7Rs are expressed by peripheral glial cells, rather than by afferent neurons. Description of functional signatures and cellular distributions of these enigmatic proteins in the peripheral nervous system (PNS) will help our understanding of ATP-dependent effects contributing to hearing loss and other sensory neuropathies.SIGNIFICANCE STATEMENT P2X7 receptors (P2X7Rs) have been the subject of much scrutiny in recent years. They have been promoted as therapeutic targets in a number of diseases of the nervous system, yet the specific cellular location of these receptors remains the subject of intense debate. In the auditory nerve, connecting the inner ear to the brainstem, we show these multimodal ATP-gated channels localize exclusively to peripheral glial cells rather than the sensory neurons, and are not evident in central glia. Physiologic responses in the peripheral glia display classical hallmarks of P2X7R activation, including the formation of ion-permeable and also macromolecule-permeable pores. These qualities suggest these proteins could contribute to glial-mediated inflammatory processes in the auditory periphery under pathologic disease states.
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