# Mechanoregulation of Ciliary Motility

> **NIH NIH R01** · HARVARD MEDICAL SCHOOL · 2024 · $415,275

## Abstract

Project Summary
Mechanoregulation is a fundamental mechanism for the control of dynamic and multiscale biological systems.
A mechanoregulatory network is responsible for the motility of cilia by converting the action of thousands of
individual dynein motors bound to doublet microtubules in the cilium into a single waveform. This waveform
has evolved to efficiently displace fluid, allowing either cell self-propulsion
or the transport of extracellular liquid
over epithelial surfaces. Ciliary motility in humans is therefore essential for the movement of sperm cells, the
removal of bacteria and viruses from the respiratory tract, and the circulation of cerebrospinal fluid in the brain.
Cilia are also used by protozoan pathogens for movement, contributing to their pathogenicity.
The biflagellate
alga, Chlamydomonas reinhardtii, has become the model system for studying the relationship between cilia
ultrastructure and ciliary motilty. Using this organism, we have determined single-particle electron
cryomicroscopy (cryo-EM) structures of the bases of dyneins and mechanoregulatory complexes natively
bound to doublet microtubules. These structures map the interconnected network of microtubules,
mechanoregulators, and dynein motors in unparalleled atomic detail. The structures reveal the mechanisms
that dock mechanoregulators to doublet microtubules and generate new hypotheses for how they control
dynein behavior. These preliminary structural studies provide a unique opportunity to better understand the
structure, function and assembly pathway of the largest mechanoregulator, the radial spoke. In aim 1, I
propose to elucidate the complete structure of a native radial spoke using cryo-EM and cross-linking mass
spectrometry. Structural information will resolve how its 20+ unique subunits interact and function together to
respond to both mechanical and chemical signals. Due to the high conservation of radial-spoke subunits
among organisms, our structure will provide insights into the etiology of ciliopathy-causing mutations in
humans. In aim 2, I propose to test hypotheses that have arisen from our “on-doublet” structures using an
interdisciplinary combination of structure-guided mutagenesis, waveform analysis by high-speed
microcinematography, and structural characterization using electron cryotomography. This work will provide
experimental evidence for the fundamental molecular mechanisms that control ciliary motility. In aim 3, I
propose to use a proteomic and structural approach to determine the mechanisms of radial-spoke assembly.
This work will test our current structure-based model of assembly and has the potential to identify the first
radial-spoke biogenesis factors. Collectively, these studies will provide unprecedented mechanistic insight into
the mechanoregulatory pathways that control ciliary motility and promises to open new avenues for the
treatment of ciliopathies.

## Key facts

- **NIH application ID:** 10824310
- **Project number:** 5R01GM141109-04
- **Recipient organization:** HARVARD MEDICAL SCHOOL
- **Principal Investigator:** Alan Brown
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $415,275
- **Award type:** 5
- **Project period:** 2021-05-01 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10824310

## Citation

> US National Institutes of Health, RePORTER application 10824310, Mechanoregulation of Ciliary Motility (5R01GM141109-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10824310. Licensed CC0.

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