@article{floyd_molines_lei_honts_chang_elting_vaikuntanathan_dinner_bhamla_2023, title={A unified model for the dynamics of ATP-independent ultrafast contraction}, volume={120}, ISSN={["1091-6490"]}, url={http://dx.doi.org/10.1073/pnas.2217737120}, DOI={10.1073/pnas.2217737120}, abstractNote={
            In nature, several ciliated protists possess the remarkable ability to execute ultrafast motions using protein assemblies called myonemes, which contract in response to Ca
            2+
            ions. Existing theories, such as actomyosin contractility and macroscopic biomechanical latches, do not adequately describe these systems, necessitating development of models to understand their mechanisms. In this study, we image and quantitatively analyze the contractile kinematics observed in two ciliated protists (
            Vorticella
            sp. and
            Spirostomum
            sp.), and, based on the mechanochemistry of these organisms, we propose a minimal mathematical model that reproduces our observations as well as those published previously. Analyzing the model reveals three distinct dynamic regimes, differentiated by the rate of chemical driving and the importance of inertia. We characterize their unique scaling behaviors and kinematic signatures. Besides providing insights into Ca
            2+
            -powered myoneme contraction in protists, our work may also inform the rational design of ultrafast bioengineered systems such as active synthetic cells.
          }, number={25}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, publisher={Proceedings of the National Academy of Sciences}, author={Floyd, Carlos and Molines, Arthur T. and Lei, Xiangting and Honts, Jerry E. and Chang, Fred and Elting, Mary Williard and Vaikuntanathan, Suriyanarayanan and Dinner, Aaron R. and Bhamla, M. Saad}, year={2023}, month={Jun} }
 @article{begley_elting_2023, title={Mitosis: Augmin-based bridges keep kinetochores in line}, volume={33}, ISSN={["1879-0445"]}, DOI={10.1016/j.cub.2022.12.037}, abstractNote={A recent study highlights the indispensability of the augmin complex for the construction of mitotic spindle bridging fibers, which in turn support accurate chromosome attachment and segregation.}, number={3}, journal={CURRENT BIOLOGY}, author={Begley, Marcus A. and Elting, Mary Williard}, year={2023}, month={Feb}, pages={R118–R121} }
 @article{floyd_molines_lei_honts_chang_elting_vaikuntanathan_dinner_bhamla_2022, title={A unified model for the dynamics of ATP-independent ultrafast contraction}, volume={10}, url={http://dx.doi.org/10.1101/2022.10.14.512304}, DOI={10.1101/2022.10.14.512304}, abstractNote={In nature, several ciliated protists possess the remarkable ability to execute ultrafast motions using protein assemblies called myonemes, which contract in response to Ca2+ions. Existing theories, such as actomyosin contractility and macroscopic biomechanical latches, do not adequately describe these systems, necessitating new models to understand their mechanisms. In this study, we image and quantitatively analyze the contractile kinematics observed in two ciliated protists (Vorticella spandSpirostomum sp), and, based on the mechanochemistry of these organisms, we propose a minimal mathematical model that reproduces our observations as well as those published previously. Analyzing the model reveals three distinct dynamic regimes, differentiated by the rate of chemical driving and the importance of inertia. We characterize their unique scaling behaviors and kinematic signatures. Besides providing insights into Ca2+-powered myoneme contraction in protists, our work may also inform the rational design of ultrafast bioengineered systems such as active synthetic cells.}, journal={[]}, publisher={Cold Spring Harbor Laboratory}, author={Floyd, Carlos and Molines, Arthur and Lei, Xiangting and Honts, Jerry E. and Chang, Fred and Elting, Mary Williard and Vaikuntanathan, Suriyanarayanan and Dinner, Aaron and Bhamla, Saad}, year={2022}, month={Oct} }
 @article{moshtohry_bellingham-johnstun_elting_laplante_2022, title={Laser ablation reveals the impact of Cdc15p on the stiffness of the contractile ring}, volume={33}, ISSN={["1939-4586"]}, DOI={10.1091/mbc.E21-10-0515}, abstractNote={ We use laser ablation to sever the constricting contractile ring of fission yeast cells and reveal the impact of Cdc15p, a putative anchoring protein, on its mechanical properties. Our work suggests that Cdc15p, and thus the anchoring mechanism, impacts the stiffness of the contractile ring more than the viscous drag. }, number={6}, journal={MOLECULAR BIOLOGY OF THE CELL}, author={Moshtohry, Mohamed and Bellingham-Johnstun, Kimberly and Elting, Mary Williard and Laplante, Caroline}, year={2022}, month={May} }
 @article{begley_medina_zareiesfandabadi_rapp_elting_2022, title={Pushing the envelope: force balance in fission yeast closed mitosis}, volume={12}, url={http://dx.doi.org/10.1101/2022.12.28.522145}, DOI={10.1101/2022.12.28.522145}, abstractNote={SUMMARY}, journal={[]}, publisher={Cold Spring Harbor Laboratory}, author={Begley, Marcus A and Medina, Christian Pagán and Zareiesfandabadi, Parsa and Rapp, Matthew B and Elting, Mary Williard}, year={2022}, month={Dec} }
 @article{zareiesfandabadi_elting_2022, title={p Force by minus-end motors Dhc1 and Klp2 collapses the S. pombe spindle after laser ablation}, volume={121}, ISSN={["1542-0086"]}, url={http://dx.doi.org/10.1016/j.bpj.2021.12.019}, DOI={10.1016/j.bpj.2021.12.019}, abstractNote={A microtubule-based machine called the mitotic spindle segregates chromosomes when eukaryotic cells divide. In the fission yeast Schizosaccharomyces pombe, which undergoes closed mitosis, the spindle forms a single bundle of microtubules inside the nucleus. During elongation, the spindle extends via antiparallel microtubule sliding by molecular motors. These extensile forces from the spindle are thought to resist compressive forces from the nucleus. We probe the mechanism and maintenance of this force balance via laser ablation of spindles at various stages of mitosis. We find that spindle pole bodies collapse toward each other after ablation, but spindle geometry is often rescued, allowing spindles to resume elongation. Although this basic behavior has been previously observed, many questions remain about the phenomenon's dynamics, mechanics, and molecular requirements. In this work, we find that previously hypothesized viscoelastic relaxation of the nucleus cannot explain spindle shortening in response to laser ablation. Instead, spindle collapse requires microtubule dynamics and is powered by the minus-end-directed motor proteins dynein Dhc1 and kinesin-14 Klp2, but it does not require the minus-end-directed kinesin Pkl1.}, number={2}, journal={BIOPHYSICAL JOURNAL}, publisher={Elsevier BV}, author={Zareiesfandabadi, Parsa and Elting, Mary Williard}, year={2022}, month={Jan}, pages={263–276} }
 @article{uzsoy_zareiesfandabadi_jennings_kemper_elting_2021, title={Automated tracking of S. pombe spindle elongation dynamics}, volume={7}, ISSN={["1365-2818"]}, url={http://dx.doi.org/10.1111/jmi.13044}, DOI={10.1111/jmi.13044}, abstractNote={Abstract}, journal={JOURNAL OF MICROSCOPY}, publisher={Wiley}, author={Uzsoy, Ana Sofia M. and Zareiesfandabadi, Parsa and Jennings, Jamie and Kemper, Alexander F. and Elting, Mary Williard}, year={2021}, month={Jul} }
 @article{elting_2021, title={Cytoskeletal biophysics: Passive crosslinker adapts to keep microtubule bundles on track}, volume={31}, ISSN={["1879-0445"]}, url={http://dx.doi.org/10.1016/j.cub.2021.04.065}, DOI={10.1016/j.cub.2021.04.065}, abstractNote={Assembly of the mitotic spindle requires dynamic adaptation and coordination among an array of motors and crosslinkers. A new study demonstrates in vitro how the mitotic crosslinker PRC1 can tune its behavior to regulate the speed of microtubule sliding.}, number={12}, journal={CURRENT BIOLOGY}, publisher={Elsevier BV}, author={Elting, Mary Williard}, year={2021}, month={Jun}, pages={R793–R796} }
 @article{begley_solon_davis_sherrill_ohi_eltinga_2021, title={K-fiber bundles in the mitotic spindle are mechanically reinforced by Kif15}, volume={32}, ISSN={["1939-4586"]}, url={http://dx.doi.org/10.1091/mbc.e20-06-0426}, DOI={10.1091/mbc.E20-06-0426}, abstractNote={ The mammalian kinetochore fiber (k-fiber) connects chromosomes to the spindle and supports segregation. We cut k-fibers by laser ablation to probe mechanical connections of microtubules within the bundle. We find that kinesin-12 Kif15 cross-links mediate k-fiber bundling. K-fiber bundling forces are in active competition with forces that cluster microtubule minus-ends. }, number={22}, journal={MOLECULAR BIOLOGY OF THE CELL}, publisher={American Society for Cell Biology (ASCB)}, author={Begley, Marcus A. and Solon, April L. and Davis, Elizabeth Mae and Sherrill, Michael Grant and Ohi, Ryoma and Eltinga, Mary Williard}, editor={Walczak, ClaireEditor}, year={2021}, month={Dec} }
 @article{zareiesfandabadi_elting_2021, title={Viscoelastic Relaxation of the Nuclear Envelope Does Not Cause the Collapse of the Spindle After Ablation in S. pombe}, url={https://spsnational.org/file/397396/download?token=AYSdz03A#page=60}, journal={Journal of Undergraduate Research in Physics}, publisher={spsnational.org}, author={Zareiesfandabadi, Parsa and Elting, Mary Williard}, year={2021} }
 @article{begley_solon_davis_sherrill_ohi_elting_2020, title={K-fiber bundles in the mitotic spindle are mechanically reinforced by Kif15}, volume={5}, url={http://dx.doi.org/10.1101/2020.05.19.104661}, DOI={10.1101/2020.05.19.104661}, abstractNote={Abstract}, journal={[]}, publisher={Cold Spring Harbor Laboratory}, author={Begley, Marcus A and Solon, April L and Davis, Elizabeth Mae and Sherrill, Michael Grant and Ohi, Ryoma and Elting, Mary Williard}, year={2020}, month={May} }
 @article{daniels_elting_2020, title={Knitting Ripples}, volume={1}, ISSN={2666-3899}, url={http://dx.doi.org/10.1016/j.patter.2020.100034}, DOI={10.1016/j.patter.2020.100034}, abstractNote={Ripples are common in both biological systems and human clothes. Knitters have long exploited the ability of fabric to curl out of plane, by either removing or adding stitches to the material as it is created. Here, we present two knitting patterns for scarves to illustrate how ripples can arise through such additive processes. Ripples are common in both biological systems and human clothes. Knitters have long exploited the ability of fabric to curl out of plane, by either removing or adding stitches to the material as it is created. Here, we present two knitting patterns for scarves to illustrate how ripples can arise through such additive processes. Humans, plants, and marine creatures are all known to decorate their margins with a bit of frill: skirts, ornamental kale, and nudibranchs all catch our eye due to their rippling edges, whether created by fashion, plant breeding, or evolution. The unifying mechanism for these ripples was identified by the work of scientists working at the University of Texas Center for Nonlinear Dynamics during the early 2000s, with the patterns (sometimes fractal!) arising from both the elastic and geometric properties of thin sheets. The central idea is non-Euclidean: if the area of a thin sheet is larger than the space available to it, it must deform out of plane, as illustrated by the scarves in Figure 1. This forms the ripples, via spontaneous symmetry breaking. Where the material is not stiff, the ripples can be readily rearranged into other ripples after they are created, which is why they are appealing on clothes: they rearrange as you move. Knitters have long exploited non-Euclidean shapes in designing garments that curve inward around our heads (positive Gaussian curvature) or outward into ripples (negative Gaussian curvature). They do this by either removing or adding stitches to the material as it is created, line by line from one edge of the garment to the other. Using such techniques, it is possible to turn the corner on the heel of a sock, or to taper the sleeve of a sweater. When one of the authors first heard about the work of Sharon et al.,1Sharon E. Roman B. Marder M. Shin G.-S. Swinney H.L. Buckling cascades in free sheets.Nature. 2002; 419: 579https://doi.org/10.1038/419579aCrossref PubMed Scopus (152) Google Scholar, 2Marder M. Sharon E. Smith S. Roman B. Theory of edges of leaves.Europhys. Lett. 2003; 62https://doi.org/10.1209/epl/i2003-00334-5Crossref Scopus (48) Google Scholar, 3Sharon E. Marder M. Swinney H. Leaves, Flowers and Garbage Bags: Making Waves.Am. Sci. 2004; 92 (https://www.jstor.org/stable/27858394): 254-261Crossref Google Scholar she turned to knitting to create a concrete demonstration of the principle. In the resulting scarf (Figure 1A), there are about 130 rows along the central spine of the scarf, but 3 times as many along each edge. These extra stitches ripple out of the plane of flat material created along the central spine. In fact, due to the way knits are constructed (row by row, zig-zagging along the fabric; see Figure 2B), there are two ways to imagine creating such a rippled scarf: from long edge to long edge, or from short end to short end. In the scarf shown in Figure 1A, the latter orientation was chosen for design reasons: the knitter had only one ball of yarn (sentimentally gifted from a fellow physics graduate student) to use to make the scarf. Using the edge-to-edge method presented two advantages: maximal use of the ball of yarn to make the scarf as long as possible and the opportunity to more immediately see that the rippling principle was working as intended. This method involves casting on enough stitches to form the width of the scarf, then periodically knitting extra, partial rows that extend from the edge of the scarf only part way in toward the spine. The line defects created by these short rows introduce negative Gaussian curvature to the fabric. A short segment of scarf illustrating this technique is shown in Figure 3A.Figure 3Illustration of the Two MethodsShow full captionA small section of scarf, created using each of the two methods.(A) This sample was knit from edge to edge (black arrow), with line-defects (magenta lines) added through the technique known as short-rows, and corresponds to the scarf in Figure 1A.(B) This sample was knit from the center line outward toward each long edge, from end to end (black arrow), with line-defects (magenta lines) added through the technique known as increasing stitches, and corresponds to the scarf in Figure 1B.View Large Image Figure ViewerDownload (PPT) A small section of scarf, created using each of the two methods. (A) This sample was knit from edge to edge (black arrow), with line-defects (magenta lines) added through the technique known as short-rows, and corresponds to the scarf in Figure 1A. (B) This sample was knit from the center line outward toward each long edge, from end to end (black arrow), with line-defects (magenta lines) added through the technique known as increasing stitches, and corresponds to the scarf in Figure 1B. The second method (Figure 1B), more conventionally used by knitters to shape garments such as sweaters or hats, is to first cast on a chain of stitches as long as the edge of the scarf is intended to be and then knit outward toward each rippled edge by adding individual stitches at regular intervals while knitting each row. Gradually, the ripples develop as the number of stitches per row grows. A sample of this technique is shown in Figure 3B, illustrating the knitting direction and the line defects where the new stitches are added. Again, these line defects are what induce the negative Gaussian curvature. To generate the second side of the scarf, you pick up the stitches from the spine and begin the process again. In this method, using up all the yarn requires casting on the correct number of stitches from the beginning. The easiest way to surmount this challenge is to knit a sample of a small number of stitches, weigh the sample, and then scale up to the total amount of yarn. Note that these two examples yield samples with a different anisotropy: the orientation of the stitches is either along the scarf or perpendicular to it, which changes how the fabric drapes and flows.4Poincloux S. Adda-Bedia M. Lechenault F. Geometry and Elasticity of a Knitted Fabric.Phys. Rev. X. 2018; 8: 21075https://doi.org/10.1103/PhysRevX.8.021075Crossref Scopus (25) Google Scholar,5Markande S.G. Matsumoto E.A. Knotty knits are tangles on tori.arXiv. 2002; (2002.01497)https://arxiv.org/abs/2002.01497Google Scholar In fact, if you look carefully at Figure 2B, you will notice that even the flattest knitting is slightly anisotropic—the fabric curls toward the front side on the top and bottom (k1 < 0 but small) and toward the backside on the sides (k2 > 0 but small). This inherent curvature has an interesting effect on our two rippled-scarf methods. In the “short-row” method, knit from edge to edge, the fabric curls toward the purled side, making the knitted side (the one normally used as the “right” side) showing. In the “increasing stitches” method, knitted from the center line outward from end to end, the scarf curls toward the knit side, leaving the purled side (the conventional “wrong” side) showing. Below, we have included knitting instructions for both versions of the scarves. The adventurous reader/knitter might be interested in extending them in a variety of ways. For example, the amount of curvature can be increased by doing more short rows with fewer stitches between them in the edge-to-edge version, or by doing more increases in the end-to-end version. Changing the stitch pattern, such as by introducing horizontal or vertical ribbing or by knitting all rows on both sides, would also change the behavior of the final scarf. These patterns will also be posted on the fiber arts community Ravelry; please join us there to share your handiwork. As shown in Figures 1 and 3, both scarves are reversible and so technically have no right (knit) or wrong (purl) side. However, we’ve used the traditional “RS” and “WS” notation to help you keep track of which side is which on the short rows. In the patterns, we use “RS” to mean the side facing the knitter on row 1. Gauge: 5 stitches/inch Cast on 24 stitches.Row 1: Knit 12, place marker, purl to end of row.Row 2: Knit 12, purl 12. Short row section 1:∗Short row 1 [RS]: Knit 6, wrap and turn 1 stitch.Short row 2 [WS]: Purl back to start of row.Short row 3 [RS]: Knit 3, wrap and turn 1 stitch.Short row 4 [WS]: Purl back to start of row.Short row 5 [RS]: Knit to marker, working wrapped stitches together with their wraps. Purl to end of row. Short row section 2:Repeat from ∗, except this time the WS and RS will be reversed since you’re starting on the WS. Repeat short row sections 1 and 2 until you’re out of yarn or scarf is desired length. Bind off all stitches knitwise. Gauge: 5 stitches/inch Cast on 200 stitches (or as many as you want your scarf to be long).Rows 1–6: Stockinette stitch (knit the RS and purl the WS).Row 7: Knit front and back in every stitch. (400 st)Row 8: Purl.Row 9: Knit.Row 10: Purl.Row 11: ∗Knit 1, knit into front and back of next stitch repeat from ∗ across. (600 st)Row 12: Purl.Row 13: Knit.Row 14: Purl. With knit side of work facing, pick up 200 stitches from the cast on edge. Repeat rows 1–14 and bind off, as for the first half of the scarf. (Note: You will knit the first row, with the purl side of the previous work facing. This way, the scarf will be symmetric.) The original impetus for knitting ripples came from conversations with Eran Sharon at the KITP workshop “Pattern Formation in Physics and Biology” (2003). Various knitting skills, materials, and ideas came from Jane Daniels, Mary Petty, Deb Romani, Wendy McRae, Samuel Poincloux, Frédéric Lechenault, Mike Dimitriyev, and Sabetta Matsumoto. Professors Karen Daniels (@karenedaniels on Twitter and @kedaniels on Ravelry) and Mary Williard Elting (@mwelting on Twitter and @melting on Ravelry) can be found knitting in various seminars and meetings at the physics department at North Carolina State University. Their more traditional interests in soft matter physics span networks, gels, granular materials, and the biophysics of cells and tissues.}, number={2}, journal={Patterns}, publisher={Elsevier BV}, author={Daniels, Karen E. and Elting, Mary Williard}, year={2020}, month={May}, pages={100034} }
 @article{zareiesfandabadi_elting_2020, title={The collapse of the spindle following ablation in S. pombe is mediated by microtubules and the motor protein dynein}, volume={10}, url={http://dx.doi.org/10.1101/2020.10.20.347922}, DOI={10.1101/2020.10.20.347922}, abstractNote={A microtubule-based machine called the mitotic spindle segregates chromosomes when eukaryotic cells divide. In the fission yeast S. pombe, which undergoes closed mitosis, the spindle forms a single bundle of microtubules inside the nucleus. During elongation, the spindle extends via antiparallel microtubule sliding by molecular motors. These extensile forces from the spindle are thought to resist compressive forces from the nucleus. We probe the mechanism and maintenance of this force balance via laser ablation of spindles at various stages of mitosis. We find that spindle pole bodies collapse toward each other following ablation, but spindle geometry is often rescued, allowing spindles to resume elongation. While this basic behavior has been previously observed, many questions remain about this phenomenon’s dynamics, mechanics, and molecular requirements. In this work, we find that previously hypothesized viscoelastic relaxation of the nucleus cannot fully explain spindle shortening in response to laser ablation. Instead, spindle collapse requires microtubule dynamics and is powered at least partly by the minus-end directed motor protein dynein. These results suggest a role for dynein in redundantly supporting force balance and bipolarity in the S. pombe spindle.}, journal={[]}, publisher={Cold Spring Harbor Laboratory}, author={Zareiesfandabadi, Parsa and Elting, Mary Williard}, year={2020}, month={Oct} }
 @article{elting_suresh_dumont_2018, title={The Spindle: Integrating Architecture and Mechanics across Scales}, volume={28}, ISSN={0962-8924}, url={http://dx.doi.org/10.1016/J.TCB.2018.07.003}, DOI={10.1016/J.TCB.2018.07.003}, abstractNote={To perform its function, the spindle must be dynamic and flexible and yet able to generate force and maintain its integrity. Active and passive molecular force generators build and maintain the spindle. New approaches are revealing new properties of each, for example, how total force output scales with the number of force generators. Molecular motors can build diverse microtubule organization modules, for example, by selectively pulling on microtubule ends or by selectively acting on antiparallel microtubule arrangements. Physical perturbations reveal how spindle material properties vary with the axis and timescale of force application, and that the spindle locally bears the load of chromosome movement. Spindle self-organization connects scales from nanometers to tens of micrometers, and from tens of milliseconds to an hour. The robust function of the spindle emerges from the feedback between its architecture, dynamics, and mechanics across scales. The spindle segregates chromosomes at cell division, and its task is a mechanical one. While we have a nearly complete list of spindle components, how their molecular-scale mechanics give rise to cellular-scale spindle architecture, mechanics, and function is not yet clear. Recent in vitro and in vivo measurements bring new levels of molecular and physical control and shed light on this question. Highlighting recent findings and open questions, we introduce the molecular force generators of the spindle, and discuss how they organize microtubules into diverse architectural modules and give rise to the emergent mechanics of the mammalian spindle. Throughout, we emphasize the breadth of space and time scales at play, and the feedback between spindle architecture, dynamics, and mechanics that drives robust function. The spindle segregates chromosomes at cell division, and its task is a mechanical one. While we have a nearly complete list of spindle components, how their molecular-scale mechanics give rise to cellular-scale spindle architecture, mechanics, and function is not yet clear. Recent in vitro and in vivo measurements bring new levels of molecular and physical control and shed light on this question. Highlighting recent findings and open questions, we introduce the molecular force generators of the spindle, and discuss how they organize microtubules into diverse architectural modules and give rise to the emergent mechanics of the mammalian spindle. Throughout, we emphasize the breadth of space and time scales at play, and the feedback between spindle architecture, dynamics, and mechanics that drives robust function. force that consumes energy and that can drive self-organization by transducing chemical energy into mechanical work. system in which the individual units are internally driven and energy consuming. pair of microtubules oriented such that their plus and minus ends point in opposite directions. design and construction of a physical structure. assembly of microtubules where ends are gathered together to form a star shape. specialized protein layer attached to the inner surface of the cell membrane that helps give the cell its overall shape. change in parts over time, such as movement, turnover, growth, or shrinkage. ability of a structure, by storing energy, to return to its original shape after being deformed. characteristic of a phenomenon whereby interactions among smaller components give rise to larger entities that exhibit properties that the smaller components do not exhibit. molecular-scale resistance that opposes motion and dissipates energy. protein structure linking chromosomes to spindle microtubules. parallel bundle of microtubules and associated proteins binding kinetochores at their plus ends and anchoring chromosomes in the spindle. force to which a given object is subjected. supporting force transmission. properties that define the response of a material to force. generation of, response to, or transmission of mechanical force. force that does not consume energy but resists object deformation in space and time. property of an object to permanently retain its deformed shape after transient force on it is removed. dimensionless value that measures the ratio of inertial forces (tendency of an object to continue its same motion under no force) to viscous forces (tendency of a fluid to resist motion of an object moving through it). order arising from self-driven parts that consume energy. bipolar array of microtubules that mediates chromosome segregation at cell division. spindle extremity, where many microtubule minus ends focus together in mammalian cells. rigidity of a structure, that is, the extent to which it resists deformation in response to force. property of materials that exhibit both viscous (i.e., frictional) and elastic characteristics when deformed. measure of resistance that opposes motion and dissipates energy, associated with structural rearrangements that lead to shape changes that remain. shape-dependent value that reflects the viscous resistance of an object moving through a fluid.}, number={11}, journal={Trends in Cell Biology}, publisher={Elsevier BV}, author={Elting, Mary Williard and Suresh, Pooja and Dumont, Sophie}, year={2018}, month={Nov}, pages={896–910} }
 @article{elting_udy_prakash_dumont_2017, title={Local Load-Bearing by Kinetochore-Fibers in the Mammalian Spindle Provides Mechanical Isolation and Redundancy}, volume={112}, DOI={10.1016/j.bpj.2016.11.2305}, abstractNote={When cells divide, microtubule bundles called kinetochore-fibers (k-fibers) attach chromosomes to the mammalian spindle. Active forces generated at kinetochores move chromosomes, and the dynamic spindle must robustly anchor k-fibers to bear this load. Where and how anchorage occurs are not understood. To spatially map load-bearing by k-fibers and determine its molecular basis, we cut k-fibers at different spindle locations and quantitatively measure residual load-bearing in different molecular backgrounds. The relaxation response immediately after ablation indicates that k-fibers are anchored not only at their ends, but along their lengths. We find that the load of k-fiber anchorage is borne very locally: longitudinally in their first few microns from kinetochores, far from poles; and laterally within 1-2 μm, without neighboring k-fibers sharing load. Depleting the microtubule crosslinker NuMA reduces local load-bearing anchorage in the spindle body, while inhibiting or depleting microtubule motor Eg5 and crosslinker PRC1 do not. A simple viscoelastic model suggests that elastic connections of k-fibers to the spindle bear the load of active kinetochore forces moving chromosomes, while centromere viscosity determines the timescale of relaxation after ablation removes load-bearing connections. Together, the data indicate that the architecture of the dynamic mammalian spindle provides k-fibers with mechanical isolation and load-bearing redundancy well-suited for robust chromosome segregation.}, number={3}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Elting, Mary Williard and Udy, Dylan B. and Prakash, Manu and Dumont, Sophie}, year={2017}, month={Feb}, pages={432a} }
 @article{elting_prakash_udy_dumont_2017, title={Mapping Load-Bearing in the Mammalian Spindle Reveals Local Kinetochore Fiber Anchorage that Provides Mechanical Isolation and Redundancy}, volume={27}, ISSN={0960-9822}, url={http://dx.doi.org/10.1016/J.CUB.2017.06.018}, DOI={10.1016/J.CUB.2017.06.018}, abstractNote={Active forces generated at kinetochores move chromosomes, and the dynamic spindle must robustly anchor kinetochore fibers (k-fibers) to bear this load. The mammalian spindle bears the load of chromosome movement far from poles, but we do not know where and how—physically and molecularly—this load distributes across the spindle. In part, this is because probing spindle mechanics in live cells is difficult. Yet answering this question is key to understanding how the spindle generates and responds to force and performs its diverse mechanical functions. Here, we map load-bearing across the mammalian spindle in space-time and dissect local anchorage mechanics and mechanism. To do so, we laser-ablate single k-fibers at different spindle locations and in different molecular backgrounds and quantify the immediate relaxation of chromosomes, k-fibers, and microtubule speckles. We find that load redistribution is locally confined in all directions: along the first 3–4 μm from kinetochores, scaling with k-fiber length, and laterally within ∼2 μm of k-fiber sides, without detectable load sharing between neighboring k-fibers. A phenomenological model suggests that dense, transient crosslinks to the spindle along k-fibers bear the load of chromosome movement but that these connections do not limit the timescale of spindle reorganization. The microtubule crosslinker NuMA is needed for the local load-bearing observed, whereas Eg5 and PRC1 are not detectably required, suggesting specialization in mechanical function. Together, the data and model suggest that NuMA-mediated crosslinks locally bear load, providing mechanical isolation and redundancy while allowing spindle fluidity. These features are well suited to support robust chromosome segregation.}, number={14}, journal={Current Biology}, publisher={Elsevier BV}, author={Elting, Mary Williard and Prakash, Manu and Udy, Dylan B. and Dumont, Sophie}, year={2017}, month={Jul}, pages={2112–2122.e5} }
 @article{elting_prakash_udy_dumont_2017, title={Mapping load-bearing in the mammalian spindle reveals local kinetochore-fiber anchorage that provides mechanical isolation and redundancy}, volume={1}, DOI={10.1101/103572}, abstractNote={Summary}, publisher={Cold Spring Harbor Laboratory}, author={Elting, Mary Williard and Prakash, Manu and Udy, Dylan B. and Dumont, Sophie}, year={2017}, month={Jan} }
 @article{karg_elting_vicars_dumont_sullivan_2017, title={The chromokinesin Klp3a and microtubules facilitate acentric chromosome segregation}, volume={216}, ISSN={0021-9525 1540-8140}, url={http://dx.doi.org/10.1083/JCB.201604079}, DOI={10.1083/JCB.201604079}, abstractNote={Although poleward segregation of acentric chromosomes is well documented, the underlying mechanisms remain poorly understood. Here, we demonstrate that microtubules play a key role in poleward movement of acentric chromosome fragments generated in Drosophila melanogaster neuroblasts. Acentrics segregate with either telomeres leading or lagging in equal frequency and are preferentially associated with peripheral bundled microtubules. In addition, laser ablation studies demonstrate that segregating acentrics are mechanically associated with microtubules. Finally, we show that successful acentric segregation requires the chromokinesin Klp3a. Reduced Klp3a function results in disorganized interpolar microtubules and shortened spindles. Normally, acentric poleward segregation occurs at the periphery of the spindle in association with interpolar microtubules. In klp3a mutants, acentrics fail to localize and segregate along the peripheral interpolar microtubules and are abnormally positioned in the spindle interior. These studies demonstrate an unsuspected role for interpolar microtubules in driving acentric segregation.}, number={6}, journal={The Journal of Cell Biology}, publisher={Rockefeller University Press}, author={Karg, Travis and Elting, Mary Williard and Vicars, Hannah and Dumont, Sophie and Sullivan, William}, year={2017}, month={May}, pages={1597–1608} }
 @article{elting_udy_dumont_2016, title={Local Anchorage of Kinetochore-Fibers to the Mammalian Spindle Provides Mechanical Isolation and Load-Bearing Redundancy}, volume={110}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/J.BPJ.2015.11.1915}, DOI={10.1016/J.BPJ.2015.11.1915}, abstractNote={During cell division, kinetochores attach chromosomes to the spindle through microtubule bundles called k-fibers. Forces generated at kinetochores move chromosomes, rather than k-fibers; thus, the latter must be structurally anchored to the spindle. How a dynamic spindle robustly anchors its k-fibers is not understood. Here, we probe where and how the mammalian spindle holds on to its k-fibers to bear the load of chromosome movement. We use laser ablation to sever k-fibers at different locations and detach them from spindle poles, thereby revealing their anchorage within the spindle body. The immediate relaxation response post-ablation indicates that k-fibers are anchored not only at their ends, but also along their lengths within the spindle. Effective anchorage scales with k-fiber length for the first few microns, but then saturates, indicating that k-fibers are effectively locally anchored within the first few microns of their lengths. This anchorage also occurs locally along the spindle's width, as little load is shared between neighboring k-fibers. We find that increasing microtubule crosslinking increases k-fiber anchorage, and that depleting NuMA, known to crosslink microtubules at poles, significantly disrupts local anchorage of k-fibers to the spindle body. In contrast, depletion of microtubule crosslinkers Eg5 and PRC1 does not affect anchorage despite these proteins’ local mechanical functions. Together, the data indicate that NuMA-mediated microtubule crosslinking in the spindle body allows for local anchorage and isolation of k-fibers, and mechanical redundancy in their connections to the spindle. Such mechanical isolation and redundancy are well-suited to ensure robust k-fiber load-bearing and chromosome segregation despite dynamic spindle forces and structures.}, number={3}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Elting, Mary W. and Udy, Dylan B. and Dumont, Sophie}, year={2016}, month={Feb}, pages={355a} }
 @article{elting_hueschen_udy_dumont_2014, title={Force on spindle microtubule minus ends moves chromosomes}, volume={206}, ISSN={1540-8140 0021-9525}, url={http://dx.doi.org/10.1083/JCB.201401091}, DOI={10.1083/JCB.201401091}, abstractNote={The spindle is a dynamic self-assembling machine that coordinates mitosis. The spindle’s function depends on its ability to organize microtubules into poles and maintain pole structure despite mechanical challenges and component turnover. Although we know that dynein and NuMA mediate pole formation, our understanding of the forces dynamically maintaining poles is limited: we do not know where and how quickly they act or their strength and structural impact. Using laser ablation to cut spindle microtubules, we identify a force that rapidly and robustly pulls severed microtubules and chromosomes poleward, overpowering opposing forces and repairing spindle architecture. Molecular imaging and biophysical analysis suggest that transport is powered by dynein pulling on minus ends of severed microtubules. NuMA and dynein/dynactin are specifically enriched at new minus ends within seconds, reanchoring minus ends to the spindle and delivering them to poles. This force on minus ends represents a newly uncovered chromosome transport mechanism that is independent of plus end forces at kinetochores and is well suited to robustly maintain spindle mechanical integrity.}, number={2}, journal={The Journal of Cell Biology}, publisher={Rockefeller University Press}, author={Elting, Mary Williard and Hueschen, Christina L. and Udy, Dylan B. and Dumont, Sophie}, year={2014}, month={Jul}, pages={245–256} }
 @article{elting_hueschen_udy_dumont_2014, title={Probing Forces on Newly Generated Spindle Microtubule Minus-Ends}, volume={106}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/J.BPJ.2013.11.100}, DOI={10.1016/J.BPJ.2013.11.100}, abstractNote={The mitotic spindle is a dynamic self-organizing machine that coordinates cell division and preserves genomic stability. The ability to focus microtubule minus-ends into poles is crucial to spindle structure and function. However, our understanding of pole-focusing forces has been limited by the challenges of labeling and imaging microtubule minus-ends in established spindles. Here, we used laser ablation to sever kinetochore-fiber microtubules in mammalian cells and probe how the cell detects and organizes newly generated microtubule minus-ends. Within a few seconds of ablation, the cell recognizes new minus-ends and begins pulling them poleward. These pole-focusing forces exist throughout metaphase and anaphase and can move chromosomes rapidly, dominating other spindle forces. Opposing forces on chromosomes from the other half-spindle are able to slow, though not stop, the pole-focusing response, as indicated by faster pole-focusing speeds in monopolar spindles and during anaphase than in metaphase bipolar spindles. Together, our data indicate that microtubule minus-end focusing forces operate broadly and rapidly and are of similar magnitude to other spindle forces. These pole-focusing forces are thus well-suited to robustly maintain spindle structural integrity despite rapid turnover of spindle components and mechanical challenges.}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Elting, Mary W. and Hueschen, Christina L. and Udy, Dylan B. and Dumont, Sophie}, year={2014}, month={Jan}, pages={9a–10a} }
 @article{hueschen_elting_udy_dumont_2014, title={Probing Forces on Newly Generated Spindle Microtubule Minus-Ends}, volume={106}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/J.BPJ.2013.11.4314}, DOI={10.1016/J.BPJ.2013.11.4314}, abstractNote={The mitotic spindle is a dynamic self-organizing machine that coordinates cell division and preserves genomic stability. The ability to focus microtubule minus-ends into poles is crucial to spindle structure and function. However, our understanding of pole-focusing forces has been limited by the challenges of labeling and imaging microtubule minus-ends in established spindles. Here, we used laser ablation to sever kinetochore-fiber microtubules in mammalian cells and probe how the cell detects and organizes newly generated microtubule minus-ends. Within a few seconds of ablation, the cell recognizes new minus-ends and begins pulling them poleward. These pole-focusing forces exist throughout metaphase and anaphase and can move chromosomes rapidly, dominating other spindle forces. Opposing forces on chromosomes from the other half-spindle are able to slow, though not stop, the pole-focusing response, as indicated by faster pole-focusing speeds in monopolar spindles and during anaphase than in metaphase bipolar spindles. Together, our data indicate that microtubule minus-end focusing forces operate broadly and rapidly and are of similar magnitude to other spindle forces. These pole-focusing forces are thus well-suited to robustly maintain spindle structural integrity despite rapid turnover of spindle components and mechanical challenges.}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Hueschen, Christina L. and Elting, Mary W. and Udy, Dylan B. and Dumont, Sophie}, year={2014}, month={Jan}, pages={787a} }
 @article{elting_leslie_churchman_korlach_mcfaul_leith_levene_cohen_spudich_2013, title={Single-molecule fluorescence imaging of processive myosin with enhanced background suppression using linear zero-mode waveguides (ZMWs) and convex lens induced confinement (CLIC)}, volume={21}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872713972&partnerID=MN8TOARS}, DOI={10.1364/OE.21.001189}, abstractNote={Resolving single fluorescent molecules in the presence of high fluorophore concentrations remains a challenge in single-molecule biophysics that limits our understanding of weak molecular interactions. Total internal reflection fluorescence (TIRF) imaging, the workhorse of single-molecule fluorescence microscopy, enables experiments at concentrations up to about 100 nM, but many biological interactions have considerably weaker affinities, and thus require at least one species to be at micromolar or higher concentration. Current alternatives to TIRF often require three-dimensional confinement, and thus can be problematic for extended substrates, such as cytoskeletal filaments. To address this challenge, we have demonstrated and applied two new single-molecule fluorescence microscopy techniques, linear zero-mode waveguides (ZMWs) and convex lens induced confinement (CLIC), for imaging the processive motion of molecular motors myosin V and VI along actin filaments. Both technologies will allow imaging in the presence of higher fluorophore concentrations than TIRF microscopy. They will enable new biophysical measurements of a wide range of processive molecular motors that move along filamentous tracks, such as other myosins, dynein, and kinesin. A particularly salient application of these technologies will be to examine chemomechanical coupling by directly imaging fluorescent nucleotide molecules interacting with processive motors as they traverse their actin or microtubule tracks.}, number={1}, journal={Optics Express}, publisher={The Optical Society}, author={Elting, Mary Williard and Leslie, Sabrina R. and Churchman, L. Stirling and Korlach, Jonas and McFaul, Christopher M. J. and Leith, Jason S. and Levene, Michael J. and Cohen, Adam E. and Spudich, James A.}, year={2013}, pages={1189–1202} }
 @article{elting_spudich_2012, title={Future Challenges in Single-Molecule Fluorescence and Laser Trap Approaches to Studies of Molecular Motors}, volume={23}, ISSN={1534-5807}, url={http://dx.doi.org/10.1016/j.devcel.2012.10.002}, DOI={10.1016/j.devcel.2012.10.002}, abstractNote={Single-molecule analysis is a powerful modern form of biochemistry, in which individual kinetic steps of a catalytic cycle of an enzyme can be explored in exquisite detail. Both single-molecule fluorescence and single-molecule force techniques have been widely used to characterize a number of protein systems. We focus here on molecular motors as a paradigm. We describe two areas where we expect to see exciting developments in the near future: first, characterizing the coupling of force production to chemical and mechanical changes in motors, and second, understanding how multiple motors work together in the environment of the cell. Single-molecule analysis is a powerful modern form of biochemistry, in which individual kinetic steps of a catalytic cycle of an enzyme can be explored in exquisite detail. Both single-molecule fluorescence and single-molecule force techniques have been widely used to characterize a number of protein systems. We focus here on molecular motors as a paradigm. We describe two areas where we expect to see exciting developments in the near future: first, characterizing the coupling of force production to chemical and mechanical changes in motors, and second, understanding how multiple motors work together in the environment of the cell.}, number={6}, journal={Developmental Cell}, publisher={Elsevier BV}, author={Elting, Mary Williard and Spudich, James A.}, year={2012}, month={Dec}, pages={1084–1091} }
 @article{sung_choe_elting_nag_sutton_deacon_leinwand_ruppel_spudich_2012, title={Single Molecule Studies of Recombinant Human α- and β-Cardiac Myosin to Elucidate Molecular Mechanism of Familial Hypertrophic and Dilated Cardiomyopathies}, volume={102}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/j.bpj.2011.11.3345}, DOI={10.1016/j.bpj.2011.11.3345}, abstractNote={Hypertrophic cardiomyopathies (HCM) and dilated cardiomyopathies (DCM) are common inherited cardiovascular diseases, often resulting from single point mutations in genes encoding sarcomeric proteins. Genetic and clinical studies have identified several hundred mutations, including severe disease causing mutations in β-myosin heavy chain (MHC). Despite the clinical significance, few single molecule studies exist for mutated β-cardiac myosin, primarily due to difficulties of heterologous protein expression and instrumental limitations. Previous studies have used mouse α-cardiac myosin or biopsies from patients. Those studies are not optimal to understand the molecular mechanism of HCM/DCM because there are significant differences between mouse α- and human β-MHC. Furthermore, biopsy samples from patients are often inhomogeneous mixtures of wildtype (wt) and mutants. This may explain why there have been many inconsistencies between the previous studies. Here, we demonstrate the first single molecule studies of recombinant human cardiac myosin. We expressed homogenous and fully functional wt human cardiac α- and β-S1 with human light chains bound. Then, we characterized the actin-myosin interaction using in vitro motility and laser beam trapping assays. From the in vitro motility assay, we measured the maximum velocity from wt α- and β-S1. Using the laser trap, we measured stroke sizes, ATP binding rates (low [ATP]) and ADP release rates (high [ATP]). Furthermore, we expressed several HCM (R403Q, S453C) and DCM (S532P) causing mutants, and obtained preliminary in vitro motility and trap data. We have built a modern version optical trap that can resolve the ∼10 nm stroke size and ∼10 ms strongly bound state of cardiac β-S1 at high [ATP]. We have further improved the resolution by implementing real-time feedback control in the system to accurately determine fine changes caused by the single mutations.}, number={3}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Sung, Jongmin and Choe, Elizabeth and Elting, Mary and Nag, Suman and Sutton, Shirley and Deacon, John and Leinwand, Leslie and Ruppel, Kathy and Spudich, James}, year={2012}, month={Jan}, pages={613a–614a} }
 @article{elting_bryant_liao_spudich_2011, title={Detailed Tuning of Structure and Intramolecular Communication Are Dispensable for Processive Motion of Myosin VI}, volume={100}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/j.bpj.2010.11.045}, DOI={10.1016/j.bpj.2010.11.045}, abstractNote={Dimeric myosin VI moves processively hand-over-hand along actin filaments. We have characterized the mechanism of this processive motion by measuring the impact of structural and chemical perturbations on single-molecule processivity. Processivity is maintained despite major alterations in lever arm structure, including replacement of light chain binding regions and elimination of the medial tail. We present kinetic models that can explain the ATP concentration-dependent processivities of myosin VI constructs containing either native or artificial lever arms. We conclude that detailed tuning of structure and intramolecular communication are dispensable for processive motion, and further show theoretically that one proposed type of nucleotide gating can be detrimental rather than beneficial for myosin processivity.}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Elting, Mary Williard and Bryant, Zev and Liao, Jung-Chi and Spudich, James A.}, year={2011}, month={Jan}, pages={430–439} }
 @article{elting_bryant_liao_spudich_2010, title={Probing Myosin-VI Processivity using Artificial Lever Arms}, volume={98}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/j.bpj.2009.12.3962}, DOI={10.1016/j.bpj.2009.12.3962}, abstractNote={The lever arm of myosin VI has an unusual composition in which two different calmodulin-binding domains, a globular three-helix bundle, and an extended single alpha-helix domain may all contribute structural roles. We wish to understand which properties of this lever arm are important for mediating intra-head communication, preventing dissociation from the actin filament, and determining the distribution of stride sizes in a processively stepping dimer. We have replaced parts of the myosin VI lever arm with alpha-actinin repeats in a series of chimeric constructs. In dimers with artifical levers arms, we have found that processivity is surprisingly robust to dramatic changes in the properties of the lever arm, even when the stride size is altered (Liao et al., JMB 2009). In new chimeric constructs, we show that limited processivity is possible even in the absence of both calmodulin-binding regions. We examine the importance of intra-head coordination for processive motion in myosin VI by comparing the predictions of simple kinetic models to measurements of run length distributions for chimeric myosins and for control contructs.}, number={3}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Elting, Mary W. and Bryant, Zev D. and Liao, Jung-Chi and Spudich, James A.}, year={2010}, month={Jan}, pages={723a} }
 @article{liao_elting_delp_spudich_bryant_2009, title={Engineered Myosin VI Motors Reveal Minimal Structural Determinants of Directionality and Processivity}, volume={392}, ISSN={0022-2836}, url={http://dx.doi.org/10.1016/j.jmb.2009.07.046}, DOI={10.1016/j.jmb.2009.07.046}, abstractNote={Myosins have diverse mechanical properties reflecting a range of cellular roles. A major challenge is to understand the structural basis for generating novel functions from a common motor core. Myosin VI (M6) is specialized for processive motion toward the (-) end of actin filaments. We have used engineered M6 motors to test and refine the "redirected power stroke" model for (-) end directionality and to explore poorly understood structural requirements for processive stepping. Guided by crystal structures and molecular modeling, we fused artificial lever arms to the catalytic head of M6 at several positions, retaining varying amounts of native structure. We found that an 18-residue alpha-helical insert is sufficient to reverse the directionality of the motor, with no requirement for any calmodulin light chains. Further, we observed robust processive stepping of motors with artificial lever arms, demonstrating that processivity can arise without optimizing lever arm composition or mechanics.}, number={4}, journal={Journal of Molecular Biology}, publisher={Elsevier BV}, author={Liao, Jung-Chi and Elting, Mary Williard and Delp, Scott L. and Spudich, James A. and Bryant, Zev}, year={2009}, month={Oct}, pages={862–867} }
 @article{wessels_elting_scimeca_weninger_2007, title={Rapid membrane fusion of individual virus particles with supported lipid bilayers}, volume={93}, ISSN={["1542-0086"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34447311691&partnerID=MN8TOARS}, DOI={10.1529/biophysj.106.097485}, abstractNote={Many enveloped viruses employ low-pH-triggered membrane fusion during cell penetration. Solution-based in vitro assays in which viruses fuse with liposomes have provided much of our current biochemical understanding of low-pH-triggered viral membrane fusion. Here, we extend this in vitro approach by introducing a fluorescence assay using single particle tracking to observe lipid mixing between individual virus particles (influenza or Sindbis) and supported lipid bilayers. Our single-particle experiments reproduce many of the observations of the solution assays. The single-particle approach naturally separates the processes of membrane binding and membrane fusion and therefore allows measurement of details that are not available in the bulk assays. We find that the dynamics of lipid mixing during individual Sindbis fusion events is faster than 30 ms. Although neither virus binds membranes at neutral pH, under acidic conditions, the delay between membrane binding and lipid mixing is less than half a second for nearly all virus-membrane combinations. The delay between binding and lipid mixing lengthened only for Sindbis virus at the lowest pH in a cholesterol-dependent manner, highlighting the complex interaction between lipids, virus proteins, and buffer conditions in membrane fusion.}, number={2}, journal={BIOPHYSICAL JOURNAL}, publisher={Elsevier BV}, author={Wessels, Laura and Elting, Mary Williard and Scimeca, Dominic and Weninger, Keith}, year={2007}, month={Jul}, pages={526–538} }