PKHD1L1 is a coat protein of hair-cell stereocilia and is required for normal hearing

Abstract

The bundle of stereocilia on inner ear hair cells responds to subnanometer deflections produced by sound or head movement. Stereocilia are interconnected by a variety of links and also carry an electron-dense surface coat. The coat may contribute to stereocilia adhesion or protect from stereocilia fusion, but its molecular identity remains unknown. From a database of hair-cell-enriched translated proteins, we identify Polycystic Kidney and Hepatic Disease 1-Like 1 (PKHD1L1), a large, mostly extracellular protein of 4249 amino acids with a single transmembrane domain. Using serial immunogold scanning electron microscopy, we show that PKHD1L1 is expressed at the tips of stereocilia, especially in the high-frequency regions of the cochlea. PKHD1L1-deficient mice lack the surface coat at the upper but not lower regions of stereocilia, and they develop progressive hearing loss. We conclude that PKHD1L1 is a component of the surface coat and is required for normal hearing in mice.

Serial scanning electron microscopy of anti-PKHD1L1 immuno-gold labeled mouse hair cell stereocilia bundles

“…As such, the MET axis for any given pair of stereocilia can vary depending on the orientation of the stereocilia and the tip links connecting them. This becomes more obvious in outer hair cell bundles, which have a more pronounced "V-shape" stereocilia arrangement within the bundle 17 .…”

“…Stereocilia are cross-linked by a number of transient or permanent links, collectively termed as stereociliary 'surface specializations' , which are identified with electron microscopy and ensure bundle integrity 1 . A list of proteins were shown to be important for the hair cell stereocilia bundle structure and function, many of which were localized to the bundle using variations of immunogold labeling protocols, and observed with electron microscopy (EM) techniques, mostly using transmission electron microscopy (TEM) [2][3][4][5][6][7][8][9][10][11][12][13][14][15] and more lately using scanning electron microscopy (SEM) [16][17][18][19][20][21] . In the most recent years though, serial electron microscopy techniques have become more accessible for use in biology, mounting a new body of work using 3D EM approaches 17,22,23 .…”

“…In a recent study, we showed that one type of stereocilia surface specialization, the stereociliary coat, is formed at least in part by a newly identified stereociliary protein, Polycystic Kidney and Hepatic Disease 1-Like 1 (PKHD1L1) 17 . This study was carried out using serial scanning electron microscopy of hair cell bundles immunolabeled with anti-PKHD1L1 and gold bead conjugated antibodies.…”

“…Although a number of organ of Corti samples were carefully evaluated using TEM, only one sample was chosen for further FIB-SEM imaging. The specificity of anti-PKHD1L1 labeling has been evaluated as part of the original study using light microscopy, SEM and TEM 17 . The serial EM datasets in this submission are of six closely located OHCs, collected from the middle cochlear turn of a P4 mouse cochlea.…”

Hybrid Plasmonics and Two-Dimensional Materials: Theory and Applications

“…204 For example, tunable frequency selective or perfectly absorbing metasurfaces allow accurate resonance tuning to perfectly match the operational condition or switching of operational frequency in signal modulation. [205][206][207] Another example is tunable beam steering which has many applications such as LIDAR and holography display 208,209 or it could be used in designing a lens with tunable focal length. 210,211 2D materials have attracted tremendous attention in the design of tunable metasurfaces due to their unprecedented properties, speci¯cally tunable Fermi level, which is done using a small bias gate voltage.…”