SemOpenAlex |

SemOpenAlex

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2984812715> ?p ?o ?g. }

Showing items 1 to 57 of 57 with 100 items per page.

W2984812715 abstract "Full text Figures and data Side by side Abstract eLife digest Introduction Results and discussion Materials and methods References Decision letter Author response Article and author information Metrics Abstract Many developmental processes break left–right (LR) symmetry with a consistent handedness. LR asymmetry emerges early in development, and in many species the primary determinant of this asymmetry has been linked to the cytoskeleton. However, the nature of the underlying chirally asymmetric cytoskeletal processes has remained elusive. In this study, we combine thin-film active chiral fluid theory with experimental analysis of the C. elegans embryo to show that the actomyosin cortex generates active chiral torques to facilitate chiral symmetry breaking. Active torques drive chiral counter-rotating cortical flow in the zygote, depend on myosin activity, and can be altered through mild changes in Rho signaling. Notably, they also execute the chiral skew event at the 4-cell stage to establish the C. elegans LR body axis. Taken together, our results uncover a novel, large-scale physical activity of the actomyosin cytoskeleton that provides a fundamental mechanism for chiral morphogenesis in development. https://doi.org/10.7554/eLife.04165.001 eLife digest Most living things have left and right sides that are not identical. A well-known example of this ‘left–right asymmetry’ is the position of the human heart within the human body. While the human heart is always on the left, in other situations it is possible for either the left side or the right side to be preferred: for example, some people prefer to write with their right hand, while others prefer to write with their left hand. In animals, left–right asymmetry starts early in the development of the embryo. A structure in cells called the cytoskeleton is known to be responsible for generating the asymmetry in many species. The cytoskeleton is mostly made of two types of proteins—rod-like proteins called microtubules and filaments of a protein called actin—but it is not clear how it is involved in establishing left–right asymmetry. The cytoskeleton has many functions in the cell: for example, it maintains the shape of the cell, it splits the contents of the cell during cell division, and it transports various things around inside the cell. The cytoskeleton is constantly moving and changing shape: all this activity involves another protein called myosin that binds to the actin filaments and moves along them to generate pulling forces. Naganathan et al. studied newly fertilized embryos of the nematode worm Caenorhabditis elegans when they contained just one cell. The experiments showed that myosin can generate turning forces that twist the actin cortical layer, leading to local rotations in the cytoskeleton that make the cell asymmetrical. This is controlled by a group of proteins called Rho proteins. Next, Naganathan et al. studied embryos that contained four cells. Again, myosin generates local rotations in the cytoskeleton, which are involved in setting up left–right body direction in this stage of development. These experiments show that changes in the cytoskeleton of individual cells can drive asymmetry in the whole embryo. The next challenge will be to understand how myosin is controlled so that rotations only occur during specific cell divisions. https://doi.org/10.7554/eLife.04165.002 Introduction Most organisms are bilaterally asymmetric with morphologically distinct left and right hand sides. Bilateral asymmetry of organisms, organs, and tissues emerges early in development and is dependent on chiral symmetry breaking of cells and subcellular structures (Hayashi and Murakami, 2001; Shibazaki et al., 2004; Danilchik et al., 2006; Xu et al., 2007; Hejnol, 2010; Tamada et al., 2010; Vandenberg and Levin, 2010; Savin et al., 2011; Taniguchi et al., 2011; Wan et al., 2011; Huang et al., 2012). In many species the primary determinant of chirality has been linked to the cytoskeleton with both the microtubule (Nonaka et al., 1998; Ishida et al., 2007) and the actomyosin cytoskeleton (Danilchik et al., 2006; Hozumi et al., 2006; Spéder et al., 2006) (AD Bershadsky, personal communication, November 2013) playing prominent roles. Generally, how chiral molecules and chiral molecular interactions generate chiral morphologies on larger scales remains to be a fundamental problem (Turing, 1952; Brown and Wolpert, 1990; Henley, 2012). For example, it has been observed that myosin motors can rotate actin filaments in motility assays (Sase et al., 1997; Beausang et al., 2008). Yet, it remains unknown which types of large-scale mechanical activities arise from such types of chiral molecular interactions. In this study, we describe that the actomyosin cytoskeleton can generate active torques at cellular scales, and that the cell uses active torques to break chiral symmetry. Results and discussion We investigated chiral behaviours of the actomyosin cell cortex in the context of polarizing cortical flow in the 1-cell Caenorhabditis elegans embryo (Munro et al., 2004; Mayer et al., 2010). The cell cortex, sandwiched between the membrane and cytoplasm, is a thin actin gel containing myosin motors and actin binding proteins (Pollard and Cooper, 1986; Clark et al., 2013). Given the chirality of cortical constituents, we first asked if cortical flow breaks chiral symmetry. We quantified the cortical flow velocity field v using particle image velocimetry in C. elegans zygotes containing GFP-tagged non-muscle myosin II (NMY-2) (Mayer et al., 2010). Flow proceeds primarily along the anteroposterior (AP) axis (x-direction), however, we also observed flow vectors to have a small component in the direction orthogonal to the AP axis (y-direction). Notably, the posterior and anterior halves of the cortex counter-rotate relative to each other (Figure 1A,B, Figure 1—figure supplement 1, Video 1), with y-velocities of ∼–2.5 μm/min and ∼1 μm/min respectively (Figure 1D). We define the chiral counter-rotation velocity vc as the difference between spatially averaged y-velocities in the posterior and the anterior region (Figure 1B) and measured vc at 858 time points during flow in 25 embryos. We find that the distribution of vc is shifted towards negative values, with a mean of −2.9 ± 0.3 μm/min (mean ± error of mean at 99% confidence unless stated otherwise, Figure 1C). Thus, counter-rotating cortical flow breaks chiral symmetry at the 1-cell stage, with the posterior half undergoing a counterclockwise rotation when viewed from the posterior pole (Figure 1A). Notably, chiral counter-rotating flow precedes the previously reported chiral whole-cell rotation of the zygote during cell division (Schonegg et al., 2014). Figure 1 with 1 supplement see all Download asset Open asset Chiral flow depends on myosin activity. (A) Sketch of a C. elegans embryo. Curved arrows illustrate chiral counter-rotating flow in the anterior (A, red) and posterior (P, green) half of the embryo, respectively. (B) Time-averaged cortical flow field (arrows) at the bottom surface of a representative C. elegans embryo viewed from the outside of the embryo in this and all other images. Arrow colors indicate y-velocity. Scale bar, 5 μm. Velocity scale arrow, 20 μm/min. (C) Histogram of instantaneous chiral counter-rotation velocity vc=〈vy〉P−〈vy〉A, where 〈vy〉A (〈vy〉P) is the average of the y-component of the velocity v over the left (right) shaded area in (B), for non-RNAi (858 frames from 25 embryos; gray) and mlc-4 (RNAi) (8 hrs; 223 frames from 7 embryos; beige). Dashed vertical lines indicate mean vc. (D) y-velocity vy along the AP axis averaged over 18 vertical stripes as indicated, for non-RNAi (black, averaged over 25 embryos) and mlc-4 (RNAi) (beige, averaged over 7 embryos). Error bars, SEM. https://doi.org/10.7554/eLife.04165.003 Video 1 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Cortical flow breaks chiral symmetry. Cortical flow during AP polarization of the C. elegans zygote exhibits chiral behaviors with the posterior and the anterior halves of the cortex counter-rotating relative to each other. https://doi.org/10.7554/eLife.04165.005 Since AP flow depends on myosin activity (Mayer et al., 2010), we asked if chiral flow does so as well. We tested if reducing myosin activity through RNAi of the myosin regulatory light-chain mlc-4 reduces the chiral counter-rotation velocity vc. We found that 8 hrs of mlc-4 (RNAi) not only reduces the AP flow velocity (Munro et al., 2004) but also significantly reduces vc (Wilcoxon rank sum test at 99% confidence; mean: −1.1 ± 0.4 μm/min, Figure 1C, Video 2) when compared to non-RNAi embryos. We conclude that chiral flow depends on myosin activity. Video 2 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Chiral flow depends on myosin activity. 8 hrs of mlc-4 (RNAi) leads to a substantial reduction of both AP and chiral flow. https://doi.org/10.7554/eLife.04165.006 We next sought to understand how myosin activity can drive both AP and chiral flow. We pursue the idea that molecular-scale torque generation (Sase et al., 1997; Beausang et al., 2008) leads to the emergence of active torques on larger scales and make use of a physical description of the cell cortex as a thin film of an active chiral fluid (Fürthauer et al., 2012, 2013). In our description, force and torque generation at the molecular scale give rise to both an active contractile tension T and an active torque density τ (Figure 2A) to drive cortical flow. Under conditions of azimuthal symmetry (Figure 2—figure supplement 1, appendix), the AP flow velocity (vx) and the y-velocity (vy) obey the equations of motion, ∂xT=η∂x2vx−γvx (1) ∂xτ=12η∂x2vy−γvy , where η is the 2D viscosity of the cortical layer and γ quantifies friction with membrane and cytoplasm (Mayer et al., 2010). From the structure of Equation 1, we see that gradients in active tension T along the AP axis drive AP flow, while gradients in active torque density τ along the AP axis drive chiral flow orthogonal to the AP axis (Figure 2B, bottom sketch). We introduce the chirality index c = τ/T, which quantifies their relative magnitude. We assume that both active tension T and active torque density τ are proportional to the local myosin concentration, leading to a single value of the chirality index c that is constant over the embryo. This remains a useful approximation even for cases where T and τ exhibit more complex dependencies on myosin concentration or where they are independently regulated (see below). In such cases the single value of c we determine corresponds to an average, capturing the overall chirality index of the embryo (see appendix). Accordingly, we calculated the theoretical AP and chiral flow profiles from the experimentally determined myosin distribution and found a best match with the experimental profiles for a hydrodynamic length of ℓ=η/γ=16±0.6 μm (Mayer et al., 2010) and an overall chirality index of c = 0.58 ± 0.09 (Figure 2B; see appendix). We conclude that a significant part of myosin activity is utilized for generating active torques. The handedness of active torques is clockwise when viewed from the outside of the embryo as indicated by the positive sign of the chirality index c. When considering the observed AP myosin gradients, active torques of this handedness give rise to counterclockwise flow in the posterior domain when viewed from the posterior tip, see Figure 2B for an illustration. Figure 2 with 1 supplement see all Download asset Open asset The cortex actively generates torques. (A) Left, myosin heads consume ATP to pull (Kron and Spudich, 1986) and twist (Sase et al., 1997; Beausang et al., 2008) actin filaments, leading to the generation of a force dipole (top, magenta) and a torque dipole (bottom, beige). Right, these can generate an active tension and an active torque density at larger scales, causing an isolated piece of cortex to contract (top) and rotate (bottom). Gray surface, membrane; cube with wire frames, non-contracted (non-rotated) piece of cortex; magenta (beige) cubes, contracted (rotated) piece of cortex. The gray arrow points from the outside to the inside of the cell and the rotation is clockwise when viewed from the outside. (B) Top, myosin intensity (blue markers) and velocity profiles (magenta markers, AP flow velocity vx; beige markers, y-velocity vy) along the AP axis (Figure 1B,D) for the non-RNAi condition (averaged over 25 embryos). Error bars, SEM. Magenta and beige curves, respective theoretical velocity profiles (c = 0.58 ± 0.09). Bottom, sketch of a C. elegans embryo with clockwise active torques in beige (as viewed from the outside of the embryo). A gradient in myosin concentration along the AP axis (see plot above) leads to a gradient in active torques (shown here with varying sizes of the clockwise torques), resulting in a chiral flow (red and green arrows) orthogonal to the gradient. https://doi.org/10.7554/eLife.04165.007 We next sought to investigate if changing myosin activity affects the overall chirality index. To this end, we performed a series of mild-to-stronger (Baggs et al., 2009) mlc-4 (RNAi) experiments with feeding times of 4, 6, and 8 hrs, respectively, and determined c for each condition. We refer to this as weak perturbation RNAi experiments as we aim to identify principle phenotypical alterations upon a mild deviation from non-RNAi conditions, similar to determining the linear response to a small perturbation. While AP flow velocity vx and the chiral flow velocity vc were generally reduced at 4 and 6 hrs of mlc-4 (RNAi) (Figure 3A, Figure 3—figure supplement 1–3, Video 3), c remained unchanged from non-RNAi conditions (c, 0.61 ± 0.07 at 4 hrs and 0.52 ± 0.06 at 6 hrs of RNAi, compared to 0.58 ± 0.09 for non-RNAi; Figure 3A, Figure 3—figure supplement 3). However, 8 hrs of mlc-4 (RNAi) not only resulted in a large reduction of both AP and chiral flow velocities but also led to a significant reduction of c (0.14 ± 0.04, Figure 3A, Figure 3—figure supplement 3). This indicates that the overall ratio of active torque density to active tension is not changed by weak reduction of mlc-4 activity but is altered at stronger RNAi conditions when cortical structure is affected (Figure 3—figure supplement 4A and Video 2). Figure 3 with 4 supplements see all Download asset Open asset Ratio of active torque to active tension is modulated by Rho. (A) Chiral counter-rotation velocity vc (top), AP velocity vx (middle), and chirality index c (bottom) for non-RNAi (gray), mlc-4 (4, 6, 8 hrs RNAi), ect-2 (4, 6, 8 hrs RNAi), and rga-3 (3, 5, 40 hrs RNAi). Error bars, error of the mean with 99% confidence. Yellow bars, significant difference to non-RNAi condition; brown bars, no significant difference. (B) Histogram of instantaneous chiral counter-rotation velocity vc for mlc-4 (left; 6 hrs; 235 frames from 7 embryos), ect-2 (middle; 6 hrs; 338 frames from 9 embryos), and rga-3 (right; 5 hrs; 402 frames from 10 embryos) RNAi. Gray histograms, non-RNAi condition. Dashed lines, mean vc. (C) Respective time-averaged cortical flow field (arrows) of representative embryos (gray, myosin). Arrow colors indicate y-velocity vy. Scale bar, 5 μm. Velocity scale arrow, 20 μm/min. (D) Respective average myosin intensity (blue markers) and velocity profiles (magenta markers, AP flow velocity vx; beige markers, y-velocity vy) along the AP axis for each RNAi condition. Error bars, SEM. Magenta and beige curves, respective theoretical velocity profiles. Dashed lines, non-RNAi theoretical velocity profiles. https://doi.org/10.7554/eLife.04165.009 Video 3 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Chirality of the cortex is unaffected under weak perturbation of myosin activity. 4 and 6 hrs of mlc-4 (RNAi) leads to a proportional change of AP and chiral flow, with the chirality index remaining unchanged under these conditions. https://doi.org/10.7554/eLife.04165.014 We next asked whether there are conditions that modify active torque generation without affecting active tension. To this end, we tested if small changes in Rho signaling, which regulates myosin activity as well as actin dynamics (Maekawa et al., 1999), have a different impact on AP and chiral flow and thus change c. We performed a series of mild-to-stronger RNAi of the Rho GEF ect-2 and the Rho GAP rga-3. We found that weak perturbation RNAi of ect-2 led to a substantial decrease in chiral but not AP flow and thus a decrease in the overall chirality index c when compared to non-RNAi conditions (Figure 3A,D; see also Figure 3—figure supplement 4B, Video 4). Conversely, weak perturbation RNAi of rga-3 led to a substantial increase in chiral but not AP flow and thus an increase in the overall chirality index c (Figure 3A,D; see also Figure 3—figure supplement 4C, Video 5). Thus, a weak perturbation of ect-2 and rga-3 affects chiral but not AP flow, unlike a weak perturbation of mlc-4 which affects both. We conclude that a principle phenotypical alteration upon mild modifications of Rho pathway activity is a change of the chirality index, or, in other words, mild modifications of Rho pathway activity change active torque generation without affecting active tension. Video 4 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Chiral flow decreases with decreasing Rho activity. ect-2 (RNAi) leads to a substantial reduction in chiral flow with a minimal change in AP flow. https://doi.org/10.7554/eLife.04165.015 Video 5 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Chiral flow increases with increasing Rho activity. rga-3 (RNAi) leads to a substantial increase in chiral flow with a minimal change in AP flow. https://doi.org/10.7554/eLife.04165.016 We next asked whether actomyosin active torques participate in bilateral symmetry breaking, since this requires a chiral process. In C. elegans, embryonic handedness is determined at the 4-cell stage when the ABa and ABp cells skew clockwise by ∼20° (as viewed dorsally in the AP–LR plane, Figure 4A) (Wood, 1991; Bergmann et al., 2003). We first tested if the clockwise skew in ABa is accompanied by chiral cortical flow. Strikingly, we observed chiral cortical flow in ABa, with the cortex in both future daughter cells counter-rotating (vc = −5.2 ± 1.1 μm/min, mean ± error of mean at 95% confidence, Video 6). The handedness of chiral flow is identical to that at the 1-cell stage, indicative of a presence of active torques with the same sign of c. If these chiral counter-rotating flows participate in the clockwise skew of both daughter cells, we would expect that changing active torque generation should affect the chiral skew at the 4-cell stage. To this end, we performed weak perturbation RNAi of the Rho pathway members, ect-2 and rga-3, to specifically modify active torques. We first tested whether chiral flows are affected at the 4-cell stage under these conditions. We found that 4.5 hrs of ect-2 (RNAi) led to a significant decrease in chiral flow velocity, vc (−3.4 ± 1.4 μm/min), while 4.5 hrs of rga-3 (RNAi) led to a significant increase in vc in the ABa cell (−6.7 ± 0.7 μm/min, Figure 4B, Video 6), similar to our observations at the 1-cell stage. We next tested whether changing chiral flow velocity at the 4-cell stage is concomitant with a change in the degree of clockwise skew. Indeed, we found that 4.5 hrs of ect-2 (RNAi) led to a significant decrease in skew (15.8° ± 4.9°) in the ABa cell measured in the AP–LR plane, while 4.5 hrs of rga-3 (RNAi) led to a significant increase in skew (37.8° ± 6.1°) when compared to non-RNAi conditions (23.6° ± 3.7°; Figure 4A and Figure 4—figure supplement 1). Similar results were obtained in ABp (Figure 4—figure supplement 1). Thus, changing counter-rotating chiral flow velocity in these cells by weak perturbation of the Rho pathway leads to a change in the degree of skew. This suggests that active torque generation and chiral counter-rotating flow participate in the execution of the LR symmetry breaking chiral skew event at the 4-cell stage. Figure 4 with 5 supplements see all Download asset Open asset Active torques participate in L/R body axis establishment. (A) A schematic of the skew angle measurement in the AP–LR plane. Gray dashed line, initial nuclei position; black dashed line, skewed nuclei position; beige arrows, direction of cortical flow on the dorsal surface (Video 6). To the right are the chiral skew angles of ABa for non-RNAi (gray), ect-2 (RNAi) (4.5 hrs) and rga-3 (RNAi) (4.5 hrs) in the AP–LR plane. Gray circles, skew angle in individual videos; shaded areas, SEM; green horizontal lines, mean skew angle; red horizontal lines, median skew angle; yellow shaded areas, knockdown conditions with a significant difference (95% confidence with the Wilcoxon rank sum test) from the non-RNAi condition. (B) Chiral counter-rotation velocity vc for non-RNAi (gray), ect-2 (RNAi) (4.5 hrs) and rga-3 (RNAi) (4.5 hrs) quantified at the 4-cell stage during ABa cytokinesis. Note that one outlier was removed for computing mean vc for rga-3 (RNAi). The expected flow profiles from our theoretical description, given a stripe of high myosin activity (corresponding to the cleavage plane), is shown in Figure 4—figure supplement 5. (C) Overall chirality index c, for non-RNAi (gray) and for Wnt signaling genes (40 hrs RNAi) that impact the establishment of the L/R body axis. Interestingly, gsk-3 not only results in a reduced chiral counter-rotation velocity but also in an increased AP velocity (Figure 4—figure supplements 2–4). Error bars, error of the mean with 99% confidence. Yellow bars, significant difference to non-RNAi condition; brown bars, no significant difference. https://doi.org/10.7554/eLife.04165.017 Video 6 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Chiral flow accompanies the LR symmetry breaking skew event at the 4-cell stage. Dorsal view of a representative 4-cell stage embryo, with ABa and ABp cells exhibiting counter-rotating cortical flow during cytokinesis, for 4.5 hrs of ect-2 (RNAi), non-RNAi and 4.5 hrs of rga-3 (RNAi). Anterior view of these Videos is shown at the bottom for visualizing counter-rotation in ABa cell. Flashing cyan arrows indicate the direction of counter-rotating cortical flow. Note that counter-rotation of AB cells is significantly reduced in ect-2 (RNAi) and significantly increased in rga-3 (RNAi) compared to the non-RNAi condition. Quantification of chiral flow velocities (Figure 4B) was performed in the ABa cell (marked in red). https://doi.org/10.7554/eLife.04165.023 Finally, we tested whether genes that affect establishment of the L/R body axis impacts chiral flow. To investigate this, we quantified chiral flow velocities and the overall chirality index c at the 1-cell stage under conditions of RNAi of the Wnt signaling genes dsh-2, gsk-3, mig-5, mom-2, and mom-5, which are known to regulate aspects of bilateral symmetry breaking (Walston et al., 2004; Pohl and Bao, 2010). Strikingly, we found that all these conditions (except mom-5) led to reduced chiral flow and a significant reduction of the overall chirality index c at the 1-cell stage (Figure 4C, Figure 4—figure supplement 2–4, Video 7). These results are indicative of a fundamental link between genes that affect LR symmetry breaking and chiral counter-rotating flow. Since Wnt-induced signals in many systems propagate through Rho GTPases to promote morphological changes (Schlessinger et al., 2009), we speculate that these effects are propagated through Rho signaling (Figure 3). Taken together, our results indicate that active torque generation and chiral counter-rotating flows participate in the establishment of the L/R body axis of C. elegans. Video 7 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Wnt signaling genes regulate chiral flow. RNAi of Wnt signaling genes leads to a substantial reduction in chiral flow. https://doi.org/10.7554/eLife.04165.024 Video 8 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as WebM Download as Ogg Chiral flow observed with an actin probe. Cortical flow visualized through Lifeact::tagRFP-T exhibits similar chiral behaviors. https://doi.org/10.7554/eLife.04165.025 To conclude, the actomyosin cytoskeleton in C. elegans generates active chiral torques with clockwise handedness when viewed from the outside of the cell. They drive a specific pattern of chiral flows which can be understood quantitatively based on the physics of active gels with chiral asymmetries (Kruse et al., 2005; Fürthauer et al., 2012, 2013). Furthermore, our weak perturbation RNAi experiments indicate that Rho activity affects cortical chirality in a way that does not depend on its role in activating myosin. On the one hand, this raises an interesting question whether active chiral torques arise directly from chiral interactions between actin and myosin (Figure 2A) or whether they rather emerge through myosin molecular force generation and non-trivial tension–torque coupling (Gore et al., 2006; De La Cruz et al., 2010) in the actomyosin network. On the other hand, through these weak perturbation RNAi experiments we have identified specific conditions under which cortical chirality and active torques can be selectively modified. Bilateral symmetry breaking requires a chiral process, and we used these specific conditions to demonstrate that in C. elegans, this chiral process could be provided by active chiral torque generation of the actomyosin cortical layer for driving the spindle skew at the 4-cell stage. We note that a plausible scenario for driving spindle skew by counter-rotating flows is similar to the rotation that a crawler excavator or a digger can execute on the spot. This is done by such a machine rotating its two chains in opposite directions. In our context, the chain rotations correspond to the counter-rotating flows and the rotation of the machine corresponds to the spindle rotation giving rise to the skew. Our results imply that active torques are generated at multiple stages during development, in the zygote during polarity establishment, without immediate consequences with respect to LR symmetry breaking, and again at the 4-cell stage, but here as an instructional and mechanistic event that helps to break left/right symmetry. Chiral morphogenetic rearrangements have been observed at other stages in C. elegans development (Pohl and Bao, 2010) and during the first cleavage (Schonegg et al., 2014; Singh and Pohl, 2014), as well as in other systems (Shibazaki et al., 2004; Danilchik et al., 2006; Géminard et al., 2014). It is interesting to speculate that all these events might be driven by active torque generation in the actomyosin layer. As such, our work paves the way for a mechanistic understanding of chiral morphogenesis of cells, tissues, and organisms. Materials and methods C. elegans strains Request a detailed protocol The following transgenic lines were used in this study: TH455 (unc-119(ed3) III; zuIs45[nmy-2::NMY-2::GFP + unc-119(+)] V; ddIs249[TH0566(pie1::Lifeact::mCherry:pie1)]) for imaging cortical flow, LP133 (nmy-2(cp8[NMY-2::GFP + unc-119(+)]) I; unc-119(ed3) III) (Dickinson et al., 2013) for imaging counter-rotation of AB cells, and SWG003 (nmy-2(cp8[NMY-2::GFP + unc-119(+)]) I; unc-119(ed3) III; gesIs002[unc-119(ed3) III; (pie-1::Lifeact::tagRFP-T::pie-1 + unc-119(+))]) for quantifying chiral flow fields with an actin probe. For imaging the chiral skew event at the 4-cell stage, a mCherry::Histone; mCherry::PH-PLC1δ1 transgenic line was generated by crossing OD70 (Kachur et al., 2008) to a line expressing Moesin::GFP and mCherry::Histone obtained from the Piano lab (New York University, New York, USA). C. elegans worms were cultured on OP50-seeeded NGM agar plates as described (Brenner, 1974). RNA interference" @default.
W2984812715 created "2019-11-22" @default.
W2984812715 creator A5049814643 @default.
W2984812715 creator A5068817583 @default.
W2984812715 creator A5080597344 @default.
W2984812715 creator A5088549673 @default.
W2984812715 creator A5091351450 @default.
W2984812715 date "2014-11-07" @default.
W2984812715 modified "2023-09-23" @default.
W2984812715 title "Author response: Active torque generation by the actomyosin cell cortex drives left–right symmetry breaking" @default.
W2984812715 doi "https://doi.org/10.7554/elife.04165.027" @default.
W2984812715 hasPublicationYear "2014" @default.
W2984812715 type Work @default.
W2984812715 sameAs 2984812715 @default.
W2984812715 citedByCount "0" @default.
W2984812715 crossrefType "peer-review" @default.
W2984812715 hasAuthorship W2984812715A5049814643 @default.
W2984812715 hasAuthorship W2984812715A5068817583 @default.
W2984812715 hasAuthorship W2984812715A5080597344 @default.
W2984812715 hasAuthorship W2984812715A5088549673 @default.
W2984812715 hasAuthorship W2984812715A5091351450 @default.
W2984812715 hasBestOaLocation W29848127151 @default.
W2984812715 hasConcept C121332964 @default.
W2984812715 hasConcept C144171764 @default.
W2984812715 hasConcept C169760540 @default.
W2984812715 hasConcept C204795200 @default.
W2984812715 hasConcept C2524010 @default.
W2984812715 hasConcept C2779886137 @default.
W2984812715 hasConcept C33923547 @default.
W2984812715 hasConcept C62520636 @default.
W2984812715 hasConcept C86803240 @default.
W2984812715 hasConceptScore W2984812715C121332964 @default.
W2984812715 hasConceptScore W2984812715C144171764 @default.
W2984812715 hasConceptScore W2984812715C169760540 @default.
W2984812715 hasConceptScore W2984812715C204795200 @default.
W2984812715 hasConceptScore W2984812715C2524010 @default.
W2984812715 hasConceptScore W2984812715C2779886137 @default.
W2984812715 hasConceptScore W2984812715C33923547 @default.
W2984812715 hasConceptScore W2984812715C62520636 @default.
W2984812715 hasConceptScore W2984812715C86803240 @default.
W2984812715 hasLocation W29848127151 @default.
W2984812715 hasOpenAccess W2984812715 @default.
W2984812715 hasPrimaryLocation W29848127151 @default.
W2984812715 hasRelatedWork W2004593538 @default.
W2984812715 hasRelatedWork W2014221891 @default.
W2984812715 hasRelatedWork W2042757809 @default.
W2984812715 hasRelatedWork W2045348531 @default.
W2984812715 hasRelatedWork W2048694657 @default.
W2984812715 hasRelatedWork W2061926843 @default.
W2984812715 hasRelatedWork W2080864321 @default.
W2984812715 hasRelatedWork W2784116815 @default.
W2984812715 hasRelatedWork W2986749557 @default.
W2984812715 hasRelatedWork W3102244034 @default.
W2984812715 isParatext "false" @default.
W2984812715 isRetracted "false" @default.
W2984812715 magId "2984812715" @default.
W2984812715 workType "peer-review" @default.