Regulation of cell shape by the cytoskeleton during tissue morphogenesis

Lead Research Organisation: MRC Laboratory of Molecular Biology

Abstract

Epithelial sheets of cells are one of the major tissue types in all animals. They also form the basic building blocks of all tubular organs, such as lungs, kidney, vasculature, in both vertebrates such as us humans, but also in invertebrates such as fruit flies. Many severe developmental defects are the result of a failure of tubes forming correctly, such as neural tube closure defects, and furthermore 80% of cancers originate from epithelial tissues. We want to dissect the basic mechanisms of how simple epithelial sheets deform in a highly coordinated manner to turn into complex tissue shapes. We use a process of tube formation in the fruit fly embryo as our main model: the formation of the tubes of the salivary glands. The macroscopic process of this tube formation is conserved and very similar to for instance the early formation of tubes in the development of lungs in mouse or humans. In contrast to vertebrates, fruit flies have the advantage of excellent genetic tools and allow easy imaging and manipulation. We use a combination of genetic methods, live imaging and computational tools to understand how healthy organs form, and his will allow us in the future to better understand the causes of diseases or malformation of tubular epithelia.

Technical Summary

Epithelia constitute one of the major tissue types in all animals and form the basic building blocks of tubular organs in both vertebrates and invertebrates. Simple epithelial sheets are also the basic starting point in the development of most animals. We want to dissect how simple epithelial sheets deform in a highly concerted manner to turn into complex tubular tissue shapes. We use the formation of the tubes of the salivary glands in the Drosophila embryos as our main model system, but have also begun to compare our findings to the related process of budding morphogenesis in embryonic mouse lungs. Coordinated changes in the shape of many neighbouring cells, as well as cell rearrangements are the major drivers of tissue formation. Cell shape changes are driven by the intracellular cytoskeleton. We have in the past shown how crosstalk between the actomyosin cytoskeleton and microtubules is crucial to maintain a pool of actomyosin that drives apical constriction of cells during tissue bending. Coordination between cytoskeletal responses between neighbouring cells allows concerted tissue-scale changes in shape, often mediated through cell-cell adhesion receptors. We discovered that the apical polarity protein Crumbs, through newly identified homophilic interactions of its extracellular domain, can determine where a multicellular actomyosin cable is formed.
The study of epithelial morphogenesis over the last decade has mostly focussed on events within the most apical portion of the cells. Our previous analysis of microtubule-actomyosin interactions and interdependence in the placode have clearly shown that structures that span the whole length of the cells, the longitudinal microtubules bundles, can have profound effects on events within the apical surface, the medial actomyosin contractions, and thus the whole cell volume and events within need to be studied. We now want to follow on from this analysis to address what happens in the remaining 90% volume of these epithelial cells during tube formation.
We plan to dissect the control of cell shape changes during tissue morphogenesis by addressing questions at different scales and integrating the information gathered at each scale:
1) At the molecular level, we will analyse how responses of different cytoskeletal systems are coordinated during cell shape changes. In particular we will analyse how the microtubule cytoskeleton influences the actomyosin cytoskeleton and what the role of cytolinker proteins is in this process.
2) At the cellular level, we will dissect how cell-cell adhesion systems, in particular Crumbs homophilic interactions, impact on the intracellular actomyosin cytoskeleton and how cytoskeletal responses are coupled between cells, such as for instance during the assembly of multicellular actomyosin cables.
3) At the tissue level, we will segment and track epithelial cells in 3D over time, to understand the contribution of different cell behaviours to morphogenesis and also to uncover novel cell behaviours that drive shape changes at the tissue scale.
We propose that the combination of approaches detailed above will give us a very detailed understanding of the cellular events that drive tube formation at the tissue level. The mutant analysis as well as the search for molecular factors driving these cellular behaviours will allow us to extend the understanding of epithelial morphogenesis from its current apical-centric view to a true 4D appreciation.

Publications


10 25 50
 
Description Morphometric analysis of tube formation in 3D 
Organisation University of Cambridge
Department Department of Pathology
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution We perform the in vivo imaging analysis, genetic analysis and conceptual ideas.
Collaborator Contribution Dr Guy Blanchard has written software allowing segmentation and tracking of cells in time-lapse movies, followed by morphometric analysis to determine strain rates as proxies of forces acting in the tissue. We are using his software and collaborating with him on expanding the analysis software and interpretation of the data.
Impact We are currently writing up a manuscript describing our joint analysis.
Start Year 2014
 
Description Artists in Residence Lunch Event (LMB, Cambridge , UK) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Artists in Residence Lunch: A postdoc from the lab participated and the participants talked about the influence of temperature on diverse aspects of every day lab work in relation to the kitchen and cooking preparation at home.
Year(s) Of Engagement Activity 2016
URL https://www.youtube.com/watch?v=kcsmf1X0n5Y&feature=youtu.be
 
Description Cambridge Science Festival (Cambridge, UK) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Cambridge Science Festival: a postdoc helped running a Microbit session for children interested in programming.
Year(s) Of Engagement Activity 2016
URL http://www.microbit.co.uk
 
Description Hosting of Artist (MRC-LMB, Cambridge, UK) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A local artists, Kate Winter, visited the LMB to sketch scenes of daily lab life. Our lab hosted her for a large part of this.
The sketches are now available to view within he LMB but will be accessible to a wider audience soon.
Year(s) Of Engagement Activity 2016
 
Description School Visit (Microscopes for Schools, Cambridge, UK) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Four researchers combined from the MRC-LMB in Cambridge and the Gurdon Institute in Cambridge took a set of microscopes into a Year 2 group at Morley Memorial Primary School, a local Primary School. With one microscope between 3 children and a variety of pre-prepared samples to look at and study the children learned about the small in comparison to the big, learned about life cycle and growing. This was combined with a presentation explaining the basics of microscopy and magnification/resolution.
Year(s) Of Engagement Activity 2016
 
Description Sic-Bar science talk (Cambridge, UK) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact a postdoc gave a lay talk about her work as part of 'Sci-Bar' (part of the Cambridge Science Festival)
Year(s) Of Engagement Activity 2016
URL http://www.sciencefestival.cam.ac.uk/events/scibar-cambridge