Clarin-1 gene transfer rescues auditory synaptopathy in model of Usher syndrome
Didier Dulon, … , Christine Petit, Aziz El-Amraoui
Didier Dulon, … , Christine Petit, Aziz El-Amraoui
Published July 9, 2018
Citation Information: J Clin Invest. 2018;128(8):3382-3401. https://doi.org/10.1172/JCI94351.
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Research Article Neuroscience

Clarin-1 gene transfer rescues auditory synaptopathy in model of Usher syndrome

Abstract

Clarin-1, a tetraspan-like membrane protein defective in Usher syndrome type IIIA (USH3A), is essential for hair bundle morphogenesis in auditory hair cells. We report a new synaptic role for clarin-1 in mouse auditory hair cells elucidated by characterization of Clrn1 total (Clrn1ex4–/–) and postnatal hair cell–specific conditional (Clrn1ex4fl/fl Myo15-Cre+/–) knockout mice. Clrn1ex4–/– mice were profoundly deaf, whereas Clrn1ex4fl/fl Myo15-Cre+/– mice displayed progressive increases in hearing thresholds, with, initially, normal otoacoustic emissions and hair bundle morphology. Inner hair cell (IHC) patch-clamp recordings for the 2 mutant mice revealed defective exocytosis and a disorganization of synaptic F-actin and CaV1.3 Ca2+ channels, indicative of a synaptopathy. Postsynaptic defects were also observed, with an abnormally broad distribution of AMPA receptors associated with a loss of afferent dendrites and defective electrically evoked auditory brainstem responses. Protein-protein interaction assays revealed interactions between clarin-1 and the synaptic CaV1.3 Ca2+ channel complex via the Cavβ2 auxiliary subunit and the PDZ domain–containing protein harmonin (defective in Usher syndrome type IC). Cochlear gene therapy in vivo, through adeno-associated virus–mediated Clrn1 transfer into hair cells, prevented the synaptic defects and durably improved hearing in Clrn1ex4fl/fl Myo15-Cre+/– mice. Our results identify clarin-1 as a key organizer of IHC ribbon synapses, and suggest new treatment possibilities for USH3A patients.

Authors

Didier Dulon, Samantha Papal, Pranav Patni, Matteo Cortese, Philippe F.Y. Vincent, Margot Tertrais, Alice Emptoz, Abdelaziz Tlili, Yohan Bouleau, Vincent Michel, Sedigheh Delmaghani, Alain Aghaie, Elise Pepermans, Olinda Alegria-Prevot, Omar Akil, Lawrence Lustig, Paul Avan, Saaid Safieddine, Christine Petit, Aziz El-Amraoui

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Figure 2

Architecture of the hearing organ in Clrn1ex4–/– mice and Clrn1ex4fl/fl Myo15-Cre+/– mice.

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Architecture of the hearing organ in Clrn1ex4–/– mice and Clrn1ex4fl/fl ...
(A–F) Hair bundle structure is affected in Clrn1ex4–/– mice but not in Clrn1ex4fl/fl Myo15-Cre+/– mice. Throughout the spiral cochlea, the OHC hair bundles of Clrn1ex4–/– mice are linear, wavy, and/or hooked in shape (B and E), contrasting with the V-shaped hair bundles in control (A and D) and Clrn1ex4fl/fl Myo15-Cre+/– (C and F) mice. Note that the upper image of IHCs in C is a crop of Supplemental Figure 3A (lower portion of P20 panel). Similar hair bundle abnormalities were observed along the entire cochlear axis between P12 and P25 (images representative of 12 mice). The stereocilia of the short row (colored in red) regressed entirely in most of the OHCs of P12 Clrn1ex4–/– mice (E), but not in those of P20 Clrn1ex4fl/fl Myo15-Cre+/– mice (F). (G) The physical coupling between the tallest stereocilia of OHCs and the overlying tectorial membrane (TM) was preserved in both Clrn1ex4–/– and Clrn1ex4fl/fl Myo15-Cre+/– mice, as shown by the presence of imprints of the stereocilia (white arrows) on the lower surface of the tectorial membrane. Scale bars: 1 μm.