Biology subjects

Shelley, M.

Publications and source records attributed to Shelley, M..

5 recordsLinked to original sources

bioRxiv2025

CCDC103-mediated assembly of the R2C complex links RUVBL1-RUVBL2 to Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a genetic disorder caused by defective cilia motility, powered by axonemal dynein motors. Assembly of these motors is facilitated by the molecular chaperone HSP90, its co-chaperone RUVBL1-RUVBL2 and adaptor proteins such as CCDC103 (aka DNAAF19). Mutations in CCDC103 identified in PCD patients impair dynein assembly, contributing to the disease pathology. Here, we present the cryo-electron microscopy structure of the human RUVBL1-RUVBL2-CCDC103 complex at 3.2[A] resolution, a chaperone assembly we refer to as R2C. It comprises a hetero-hexameric RUVBL1-RUVBL2 ring bound to three CCDC103 molecules via their RUVBL2-binding domains (RBDs), which have additional functions. Unlike RPAP3 of R2TP, a previously defined co-chaperone of HSP90, CCDC103 lacks a PIH1D1-binding motif and TPR domains, but its flexible N-terminal region regulates RUVBL1-RUVBL2 oligomerisation. Our characterisation of the R2C complex presented here enhances understanding of the intricate protein network involved in Hsp90-mediated assembly of dynein motors and how adaptor mutations contribute to PCD.

biochemistry↗

bioRxiv2025

The physical consequences of sperm gigantism

The male fruit fly produces [~] 1.8 mm long sperm, thousands of which can be stored until mating in a [~] 200 {micro}m sac, the seminal vesicle [1, 2]. While the evolutionary pressures driving such extreme sperm (flagellar) lengths have long been investigated [3-7], the physical consequences of their gigantism are unstudied. Through high-resolution three-dimensional reconstructions of in vivo sperm morphologies and rapid live imaging, we discovered that stored sperm are organized into a dense and highly aligned state. The packed flagella exhibit system-wide collective material flows, with persistent and slow-moving topological defects; individual sperm, despite their extraordinary lengths, propagate rapidly through the flagellar material, moving in either direction along material director lines. To understand how these collective behaviors arise from the constituents nonequilibrium dynamics, we conceptualize the motion of individual sperm as topologically confined to a reptation-like tube formed by its neighbors. Therein, sperm propagate through observed amplitude-constrained and internally driven flagellar bending waves, pushing off counter-propagating neighbors. From this conception, we derive a continuum theory that produces an extensile material stress that can sustain an aligned flagellar material [8-10]. Experimental perturbations and simulations of active elastic filaments verify our theoretical predictions. Our findings suggest that active stresses in the flagellar material maintain the sperm in an unentangled, hence functional state, in both sexes, and establish giant sperm in their native habitat as a novel and physiologically relevant active matter system.

biophysics↗

bioRxiv2023

Clustering of cortical dynein regulates the mechanics of spindle orientation in human mitotic cells

The forces which orient the spindle in human cells remain poorly understood due to a lack of direct mechanical measurements in mammalian systems. We use magnetic tweezers to measure the force on human mitotic spindles. Combining the spindles measured resistance to rotation, the speed it rotates after laser ablating astral microtubules, and estimates of the number of ablated microtubules reveals that each microtubule contacting the cell cortex is subject to [~]1 pN of pulling force, suggesting that each is pulled on by an individual dynein motor. We find that the concentration of dynein at the cell cortex and extent of dynein clustering are key determinants of the spindles resistance to rotation, with little contribution from cytoplasmic viscosity, which we explain using a biophysically based mathematical model. This work reveals how pulling forces on astral microtubules determine the mechanics of spindle orientation and demonstrates the central role of cortical dynein clustering. HighlightsO_LICytoplasmic viscosity does not determine the spindles resistance to rotation C_LIO_LIEach astral microtubule that contacts the cell cortex is pulled on by a single dynein motor C_LIO_LIPulling forces on astral microtubules determine the mechanics of spindle orientation C_LIO_LIThe mechanics of spindle orientation is regulated by clustering of dynein motors at the cell cortex C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=178 HEIGHT=200 SRC="FIGDIR/small/557210v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@56e8daorg.highwire.dtl.DTLVardef@1d16449org.highwire.dtl.DTLVardef@f3006org.highwire.dtl.DTLVardef@119f6aa_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

Self-organized intracellular twisters

Life in complex systems, such as cities and organisms, comes to a standstill when global coordination of mass, energy, and information flows is disrupted. Global coordination is no less important in single cells, especially in large oocytes and newly formed embryos, which commonly use fast fluid flows for dynamic reorganization of their cytoplasm. Here, we combine theory, computing, and imaging to investigate such flows in the Drosophila oocyte, where streaming has been proposed to spontaneously arise from hydrodynamic interactions among cortically anchored microtubules loaded with cargo-carrying molecular motors. We use a fast, accurate, and scalable numerical approach to investigate fluid-structure interactions of 1000s of flexible fibers and demonstrate the robust emergence and evolution of cell-spanning vortices, or twisters. Dominated by a rigid body rotation and secondary toroidal components, these flows are likely involved in rapid mixing and transport of ooplasmic components.

biophysics↗

bioRxiv2022

Modeling epithelial tissue and cell deformation dynamics using a viscoelastic slab sculpted by surface forces

I.During morphogenesis, epithelial monolayers actively alter their shape to create future body parts of the animal; this makes the epithelium one of the most active and critical structures in early animal development. Even though epithelial cells exist and move in three dimensions, mathematical models frequently describe them as merely two-dimensional. However, recent imaging technology has begun to reveal pertinent dynamics in the third dimension of the tissue. With the importance of the third dimension in mind, we have developed a self-sculpting, three-dimensional model of epithelia whose dynamics are driven by active forces on its surface. We present a first, fundamental study for a reduced version of epithelia that investigates how surface forces affect its internal dynamics. Our model captures the 3D slab-like geometry of epithelia, viscoelasticity of tissue response, fluid surroundings, and driving from active surface forces. We represent epithelial tissue as a thick slab, a 3D continuum comprised of a Stokes fluid with an extra viscoelastic stress. Employing this model, we present both analytical and numerical solutions of the system and make quantitative predictions about cell shapes, cell dynamics, and the tissues response to surface force in a three-dimensional setting. In particular, we elucidate the initiation of ventral furrow invagination and T1 transitions in Drosophila embryogenesis. In the former, we demonstrate the importance of fluid and geometric surroundings to drive invagination. In the latter, we show the limitations of surface forces alone to drive T1 transitions.

biophysics↗