Award details

Dissecting the regulation and function of actin flows during cell motility

Reference	BB/V006169/1
Principal Investigator / Supervisor	Dr Brian Stramer
Co-Investigators / Co-Supervisors
Institution	King's College London
Department	Randall Div of Cell and Molecular Biophy
Funding type	Research
Value (£)	660,596
Status	Current
Type	Research Grant
Start date	01/09/2022
End date	31/08/2025
Duration	36 months

Abstract

Actin flows are a ubiquitous feature of migrating cells and critical for cellular force generation during tissue morphogenesis. However, we are only starting to understand how actin flows are regulated and coordinated with other signalling pathways during these processes. This proposal will exploit our unique capacity to live image global actin flows during Drosophila embryonic hemocyte migration to begin to understand how actin flows are integrated with other cytoskeletal components and signalling pathways to control polarity and cell motility. This will be accomplished by examining Drosophila mutants for hypothesised cytoskeletal effectors and subsequently dissecting the changes in actin flow dynamics and cell migration parameters. In the first Objective we will characterise acto-myosin flow organization and dynamics during hemocyte behaviours in vivo to determine how changes in actin flows are modulated during establishment of cell polarity and persistent motility. We will also examine how acto-myosin flows are coordinated with the dynamics of the microtubule network, which is also known to be a critical regulator of cell polarity. In the next Objective we will examine the role of hypothesised effectors of the actin and microtubule network in controlling the organization of actin flows during hemocyte motility. This will allow us to determine how actin crosslinking, bundling, and turnover, as well as microtubule polymerisation is controlling the global actin flow profile of polarised cells. In the final Objective we will examine how Moesin, a known regulator of the rear of migrating cells, is integrated with the actin flow machinery. We will determine how a loss of Moesin effects cell migration and actin flow and examine how the flowing actin network is coordinating the activity of this polarity factor.

Summary

Cell migration is a fundamental cellular behaviour that occurs during normal physiology, such as embryogenesis, as well as pathologies, such as cancer metastasis. Understanding how cells control their movement is therefore important for numerous fundamental biological processes and is of translational relevance. For the past 50 years our view of cell migration has involved a step-wise cycle of subcellular behaviours beginning with extension of the membrane at the front of the cell. However, recent evidence in a number of cell types has revealed that the leading edge is instantaneously coordinated with other 'steps' of the migratory cycle: cell motility is therefore not a step-wise process. Our goal now is to understand how these migratory behaviours are coordinated in space and time to control cell motion. Our laboratory has pioneered the use of embryonic Drosophila macrophages (hemocytes) as an in vivo migration model to address fundamental processes controlling cell motility. These cells can be live imaged at very high resolution within the animal, and coupled with the genetic tractability of the fruitfly, this system is therefore a powerful model to understand the control of cell motility during normal physiology. Using this model we have recently revealed that the actin cytoskeletal network, which is known to be the driver of cell motility, undergoes constant flow within hemocytes. Through the development of computational tools we have revealed that this actin flow is highly coordinated across the entire cell resulting in stable sinks within the flowfield that appear to control actin flows across the cell and direct cell motion. We hypothesise that this orchestrated actin flow is a critical factor that controls the subcellular behaviours involved in cell migration, which will be dissected in further detail in this proposal. As actin flows are a central feature of all migrating cells, the results of this work will be relevant to many biological processes. Inthe first Objective we will further develop our computational tools to analyse actin flows and subsequently use these novel approaches to determine the timecourse of actin flow changes during normal hemocyte behaviours, such as responses to wound signals. We will also investigate how actin motion is correlated with the movement of myosin, a critical motor responsible for contraction and subsequent flow of the actin network. The results of this objective will form a baseline understanding that will allow us to precisely determine the function of regulators in subsequent objectives. In the next Objective we will examine how actin flows are regulated by testing flies containing mutations in genes hypothesized to control the actin network. Additionally, we will examine how the motion of the actin network is controlling and/or coordinated by the microtubule network, a second cytoskeletal network that is important in cell migration. Again, fly lines containing mutations in known regulators of the microtubule network will be tested to determine how this network is regulating actin motion. In the final Objective we will examine how actin flow may be directly controlling the activity of a regulator of cell migration responsible for defining cell polarity. Moesin is an actin regulator known to localize to the rear of many migratory cell types where it controls polarised motility. Preliminary data reveals that moesin localises to the rear of migrating hemocytes and that moesin mutants have defects in cell movement and actin flow. Previous mathematical modelling has suggested that any protein that binds to the actin network with sufficient strength will be carried rearward by the actin flow resulting in a gradient that may subsequently control cellular behaviour. We hypothesise that moesin is an ideal candidate for such direct regulation by actin flow and we will examine how moesin is controlled by the flow and subsequently feeds back to control the actin network.

Committee	Research Committee C (Genes, development and STEM approaches to biology)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

I accept the terms and conditions of use (opens in new window)

export PDF file

back to list new search