Transgenic Tg(Kcnj10-ZsGreen) fluorescent reporter mice allow visualization of intermediate cells in the stria vascularis

Abstract

The stria vascularis (SV) is a stratified epithelium in the lateral wall of the mammalian cochlea, responsible for both endolymphatic ion homeostasis and generation of the endocochlear potential (EP) critical for normal hearing. The SV has three layers consisting predominantly of basal, intermediate, and marginal cells. Intermediate and marginal cells form an intricate interdigitated network of cell projections making discrimination of the cells challenging. To enable intermediate cell visualization, we engineered by BAC transgenesis, reporter mouse lines expressing ZsGreen fluorescent protein under the control of Kcnj10 promoter and regulatory sequences. Kcnj10 encodes KCNJ10 protein (also known as Kir4.1 or Kir1.2), an ATP-sensitive inwardly-rectifying potassium channel critical to EP generation, highly expressed in SV intermediate cells. In these transgenic mice, ZsGreen fluorescence mimics Kcnj10 endogenous expression in the cochlea and was detected in the intermediate cells of the SV, in the inner phalangeal cells, Hensen’s, Deiters’ and pillar cells, in a subset of spiral ganglion neurons, and in glial cells. We show that expression of the transgene in hemizygous mice does not alter auditory function, nor EP. These transgenic Tg(Kcnj10-ZsGreen) mice allow live and fixed tissue visualization of ZsGreen-expressing intermediate cells and will facilitate future studies of stria vascularis cell function.

Role of Kir4.1 Channel in Auditory Function: Impact on Endocochlear Potential and Hearing Loss

“…The KCNJ10 gene encodes the Kir4.1 channel, expressed in glial cells of the brain and kidney, but also in the inner ear, particularly in the lateral cochlear wall, spiral ganglion cells, and supporting cells in the organ of Corti [22][23][24] (Figure 2). This channel, also known as inactivable internally rectified potential 4.1, is an important component of the ion channels in the cochlea, crucial to maintaining ion homeostasis and for the generation and maintenance of the cochlear EP, critical for sound transduction in the inner ear [11,14,[22][23][24][25][26][27][28]. The loss of endocochlear potential and degeneration of inner ear structures result in profound deafness and decreased acoustic responses in mice that lack KCNJ10 [14,29].…”