Article activity feed

  1. Evaluation Summary:

    Cell movement is essential for development and tissue homeostasis. While the cellular machineries involved in movement have been well studied, how cells maintain a persistent direction of motion is less well understood. Here, Coppey's team shows that movement persistence emerges from the coupling of two cellular systems: protrusions at the leading edge and polarity of secretion. This coupling is controlled by the small GTPase Cdc42. The authors propose a physical model that recapitulates the coupling, defines two key parameters and explains persistent cell migration.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 and Reviewer #2 agreed to share their names with the authors.)

    Was this evaluation helpful?
  2. Reviewer #1 (Public Review):

    Golgi secretion has been shown previously to be involved in cell migration, but the notion has been disputed. In this study, Vaidziulyte et al define a role of directed secretion in persistent cell migration, defined as directionality sustained beyond 20 minutes. They show that the direction of migration tends to align with the nucleus Golgi axis. This correlation is due to the Golgi reorienting towards the direction of movement of the cell. They show that cells with persistent motion display sustained polarized trafficking towards protrusion. They use ontogenetically controlled Cdc42 to show that Cdc42 rich protrusions are able to induce the reorientation of the Golgi. Finally, they propose a minimal model where coupling protrusive activity and polarised trafficking is able to recapitulate persistent migration.

    The manuscript thesis is well supported by quality imaging, quantitative analysis, use of optogenetics and modelling. However, while the analysis of the processes is of high quality, the novelty of the findings is not highlighted and not always very apparent, as many of the ideas have been discussed before in the literature. In addition, the authors did not image, study or discuss much the microtubule network, whose re-organisation is an obvious link between protrusions and Golgi re-orientation. Finally, it is not clear how the physical model yields testable predictions for future experimentations.

    Was this evaluation helpful?
  3. Reviewer #2 (Public Review):

    In this paper, the authors are primarily concerned with the bidirectional link between directed secretion from the Golgi (the Nucleus-Golgi polarity axis), and events on the cell membrane associated with protrusive activity. They label the Golgi complex and track migrating cells, showing that the Nucleus-Golgi axis aligns to the direction of motion.

    Interestingly, when cells are first confined to a circular adhesion patch, and then allowed to escape, the direction of escape correlates with the NG polarity axis. The authors treat cells with microtubule-disrupting nocodazol (NZ), finding decreased migratory persistence. Using maps of morphodynamic and of Rab6-labeled Golgi secretion (trafficking maps), they find that protrusion precedes trafficking. They optogentically stimulate protrusion by activating Cdc42, showing downstream reorientation of the nuclear-golgi axis that is faster in circular confined cells that in free-moving cells.

    Finally, the authors describe a minimal model to fit their data to two parameters that govern the feedback between the axis of polarity and the protrusive activity.

    The strengths of the paper are the experimental data and the interesting tracking of cells with and without confinement, with and without MT disruption, and with ontogenetic stimuli.

    In general, it is well known that cell polarity and persistent migration are complex phenomena with multiple layers of regulation and feedback. The activities of GTPases, the feedback from F-actin, crosstalk and delivery of GEFs/GAPs along microtubules, effects of PI3K, PTEN, of lipids, and multiple interacting factors together determine the persistence and responsiveness of cells to stimuli. It is also clear that once a polarity axis of some kind is established (whether due to cytoskeleton assembly, cell shape, or organelle placement) it too, participates in the overall orchestration of cell migration and feedback to polarity persistence. Here the authors have attempted to isolate the Nucleus-Golgi axis as an important factor, while not entirely evaluating its importance relative to other factors. For example, could the NZ treated cells simply have distinct GEF/GAP activities? Is the lack of persistence in such cells explainable only by trafficking defect?

    The authors point to the fact that cell polarity and cell migration have been modelled by many others previously. This is indeed true, aa this is a field with much literature. The authors briefly mention some reviews. Many previous papers have attempted to pose hypotheses for what initiates or what maintains (or changes) polarity, and many have explored specific hypotheses for molecular interactions. In contrast, the model here is very minimal, which can be an advantage (only 2 parameters needed to fit the data). At the same time this minimality also means that there is no clear mechanistic hypothesis to test, other than the relatively well known fact that protrusion and polarity feed back on one another.

    The model essentially depicts cell edge activity by "transfer function" responses to stimuli and axis rotation by a linear combination of forces (basal and protrusive). Nowhere in the model is the secretory property of the Golgi, or indeed any specific property of the NG axis used. In short, the "axis" could just as easily relate to any other structural cell property that responds to force. This is a drawback. It would be interesting to determine what the two feedback parameters represent specifically in terms of molecular effects associated with the Golgi-nuclear axis that is unique to that axis, for example. This could possibly be achieved by starting with a more detailed model (V1) and showing that it reduces to the minimal model here, while connecting some specific molecular details to the forces or the effect of the NG axis on the cell edge activity.

    Finally, the authors have made a specific choice of representing stimuli by transfer functions, which is fine. However, it would be worth pointing out here, that this is merely one way of representing the spread of GTPase activity on the cell membrane, and that it fits well within the class of models utilizing reaction-diffusion equations to describe GTPase activity in cells. (This link would help to put the model into the context of the broader literature on the subject.)

    Was this evaluation helpful?
  4. Reviewer #3 (Public Review):

    The manuscript of Vaidziulyte et al. investigates the dynamic and causal relationship between peripheral cell protrusions and the sequential events leading to the establishment of cell polarity to sustain persistence migration. Moreover, this causal analysis led to the development of a minimal physical models highlighting the importance and properties of feed-backs between protrusions and the force that control nucleus-Golgi axis on the induction of migration persistency.

    The originality of this manuscript is to develop a real causal study between cell protrusion, secretion and nucleus-Golgi orientation during long-term and persistance migration. The data are obtained and supported through state-of the-art approaches to follow and quantify migration over-time, very elegant correlation analysis, specific and dynamic control of a key regulator of cell polarity establishment, CDC42. Finally, the multiple and punctilious quantification appeared essential to sustain the development of a minimal physical model that present high interest, based on its ability to mimic clear features of observed migration behaviors with limited numbers of parameters. This manuscript is supported by many past references that appeared revisited through the help of this elegant quantitative approach. Clearly, activable adhesion on cell constrained on micro- pattern demonstrated the relationship between cell protrusions and nucleus-Golgi alignement with direction of migration. As suggested by previous studies, low concentration nocodazole treatment showed that MT dynamics was essential to connect cell protrusions and reorientation of nucleus-Golgi during persistency induction. Indeed, MT dynamics is essential to sustain secretion mechanisms that were observed with secretion of Collagen X through the RUSH system or following Rab6 vesicles outside the Golgi apparatus.

    The ability of CDC42 optogenetics activations to induce nucleus-Golgi reorientation in free cells or confined cells on micro pattern clearly confirmed the importance of this small GTPase in polarity establishment.

    Finally, the manuscript integrates all these parameters to develop a minimal physical model between CDC42-cell-protrusion-Nucleus/Golgi reorientation and cell persistency.

    Was this evaluation helpful?