# Molecular Basis of Hair Cell Stereocilia Bundle Morphology

> **NIH NIH R01** · MASSACHUSETTS EYE AND EAR INFIRMARY · 2020 · $660,965

## Abstract

Summary – Abstract
Using a novel database of proteins actively synthesized in mouse inner ear sensory hair cells shortly after birth,
we have identified a novel hearing loss protein, Polycystic Kidney and Hepatic Disease 1-Like 1 (PKHD1L1),
previously not shown to participate in hair cell function, or localized to hair cell stereocilia bundles. By specifically
removing PKHD1L1 from mouse inner ear sensory hair cells, we show that absence of PKHD1L1 results in
hearing loss. In order to understand the mechanism by which PKHD1L1-deficient mice develop hearing loss, three closely
coupled aims are proposed for this study. Since PKHD1L1 has not been previously shown to participate in hair
cell function, or been localized to hair cell stereocilia bundles, in Aim 1 we will localize PKHD1L1 on the surface
of mouse hair cell stereocilia during bundle maturation (i.e. within the first three weeks after birth), using highly
precise electron microscopy protein localization techniques. Our preliminary immunogold antibody labeling
results localize PKHD1L1 to the tips of stereocilia at postnatal day 4. In Aim 2 we test the function of PKHD1L1
by evaluating the hearing deficit of the hair cell-specific PKHD1L1 knock-out mouse. We show that ‘stereocilia
coat’ is absent from the tips of PKHD1L1-deficient stereocilia. We will now specifically focus on the implications
of PKHD1L1-deficiency on development of tectorial membrane attachment crowns, bundle cohesion, bundle
motion upon stimulation, and the properties of the hair cell transduction current. By studying a PKHD1L1-
deficient mouse line without the ‘coat’ at the tips of stereocilia, we propose a clean experimental paradigm to
test PKHD1L1’s (hence, the coat’s) contribution to bundle cohesion, and sliding adhesion. Lastly, in our Aim 3,
based on the predicted domain structure of PKHD1L1 suggesting possible homomeric (i.e. with itself) and
heteromeric (with other proteins) interactions, we will perform protein interaction experiments to reveal possible
interactions with other proteins involved in forming the tectorial membrane or its attachment to stereocilia, like
stereocilin, CEACAM16 and tectorin.

## Key facts

- **NIH application ID:** 9976490
- **Project number:** 5R01DC017166-03
- **Recipient organization:** MASSACHUSETTS EYE AND EAR INFIRMARY
- **Principal Investigator:** Artur Indzhykulian
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $660,965
- **Award type:** 5
- **Project period:** 2018-08-01 → 2023-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9976490

## Citation

> US National Institutes of Health, RePORTER application 9976490, Molecular Basis of Hair Cell Stereocilia Bundle Morphology (5R01DC017166-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9976490. Licensed CC0.

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