Hearing Loss Associated with Impaired Potassium Homeostasis in a Mouse Model of DFNA2 Deafness

SPITZMAUL, GUILLERMO

Buenos Aires

Jornada; Humboldt Colloquium ?Shaping the Future of German-Argentinian Scientific Cooperation ? The Role of Curiosity-Driven Research?; 2018

Alexander von Humobldt Foundation

Potassium channels in sensory and cardiac systems.My group investigates the functional role of potassium channels in sensory systems and heart. Specifically, we work on voltage-activated potassium channels of the Kv7 family, namely KCNQs. These channels are present in many cell types fulfilling different roles. There are five members in the KCNQ family, KCNQ1-5. KCNQ1 is mainly expressed in cardiac cells, whereas KCNQ2-5 generate currents in many neurons and primary sensory cells. KCNQ4 is expressed in hair cells of the cochlea, postsynaptic calyx afferent of vestibular type I hair cells and in some nuclei of the auditory tract. We are currently using KCNQ4 transgenic mice to determine the role of this channel in several tissues and as a model to evaluate pharmacological treatments for diseases generated by mutations in this channel gene. In cochlea, KCNQ4 is expressed mainly in the basal pole of the outer hair cells, where it extrudes potassium ions that enter through the apical membrane during sound transduction. The absence of the KCNQ4 current leads to malfunction of outer hair cells, leading to cell degeneration and death, with the corresponding hearing loss. In humans, KCNQ4 mutations generate DFNA2 deafness thus, we found appropriate to use a knock-in mouse that carries an equivalent human mutation, to model DFNA2 disease. To do so, we are characterizing the progression of cell death in the different regions of the cochlea, investigating the intracellular molecular effectors that gate this process as well as the role of efferent innervation in modulating K+ transit. In addition, we are analyzing the effect of specific potassium channel openers that could slow-down tissue degeneration. KCNQ4 has also been reported to be expressed in eye. So, using the KCNQ4 knock-out mouse, we are analyzing the expression pattern of this channel in several eye tissues and its role in visual transduction. It should be highlighted that several reports implicate KCNQ channels in some kinds of myopia, although the mechanism is not still understood. Besides our basic research, we are also involved in clinical studies with regional medical services to develop molecular biology tests for arrhythmogenic young patients that could potentially bear mutations in KCNQ1 channels. This channel is expressed in cardiac muscle cells and when mutated, it generates a prolongation of the repolarization phase of the cardiac action potential, leading to a condition called Long QT syndrome. Affected patients may suffer severe arrhythmias which may lead to syncope and sudden death. In Argentina, no genetic studies for these disease are carried out and its prevalence is unknown. For this reason, our laboratory has developed molecular tests for this condition and has started to analyze clinically diagnosed patients for Long QT syndrome.