KCNQ4 channel is required for outer hair cell survival, postnatal maturation and efferent innervation

SPITZMAUL, G.; RIAS E.; CARIGNANO C; CASTAGNA V.; VERA M.; STUPNIKI, S.; GOMEZ-CASATI E.; DIONISIO, L.

Belém

Congreso; 3rd FALAN Congress 2022; 2022

FALAN

INTRODUCTIONKCNQ4 is a voltage-gated K channel essential for hearing. Impairment of its function produces a chronic depolarization of hair cells (HC)leading to cell death, and hearing loss (HL). The mechanism of cell death remains unknown. A protective pathway is carried out by theefferent system by the activation of its synapses, restoring membrane potential. However, its contribution to KCNQ4-related HL isunknown.OBJECTIVESOur aim is to evaluate the molecular, tissue and functional alterations of HCs and their efferent connectivity in a mouse model of HL,which is a knock-out for the KCNQ4 channel (Kcnq4 ) (Nº083/2016).METHODSIn the WT and Kcnq4 mice we performed immunofluorescence (IF) combined with superresolution-confocal microscopy, quantitativePCR (qPCR), Auditory brainstem response (ABR) and Distortion product of otoacoustic emissions (DPOAE) assays.RESULTSIn 4 postnatal-weeks-old (W) Kcnq4 animals, using IF, we found an increase of cleaved CASPASE-3 expression in outer hair cells (OHC)from the basal turn. Moreover, qPCR analysis revealed that the expression ratio between the pro- and anti-apoptotic factors Bax/Bcl2 was~76-fold higher. We also found mislocalization of the membrane protein PRESTIN and of the efferent synapses (~30%) that contact OHC.Furthermore, we found no changes in terminals volume but a 40% decrease in the number of synapses/OHC in Kcnq4 mice. By contrast,both genotypes at 2W exhibited the same immature wiring pattern. To test the hearing function, we performed ABR showing a significantthreshold shift of 20-48 dB SPL in the 5.6-45.25 kHz frequency range. Besides, DPOAE test revealed a threshold shift of ~12-20 dB SPL inthe 8-45.25 kHz range.CONCLUSIONSWe found new insights into the mechanism of HL in the Kcnq4 mice. While the basal OHCs die by apoptosis, hearing function is impairedin all cochlear regions.