Epithelial morphogenesis and cell polarity

Lead Research Organisation: University College London

Abstract

"Epithelial cell polarity specification and maintenance is a key problem in cell biology. The vast majority of cancers in human originate from epithelia (i.e. Breast, Colon, Lung, Kidney, etc.) and a major hallmark of tumourogenesis is a progressive loss of epithelial cell polarity. We are studying this problem using the fruit fly Drosophila melanogaster, coming with an unparalleled genetic toolbox, and thus allowing us to manipulate the function of virtually every single gene present in its genome. While up to 80% of the genes associated with diseases in human are conserved in Drosophila, they are often present as one single gene, which is ideal to study a gene function, as very little redundancy is present. Using this approach, we are making significant progresses toward characterizing the molecular basis for establishing and maintaining epithelial cell polarity. This is particularly relevant for better tackling the process of tumorogenesis and metastasis, as these are characterized by a loss of epithelial cell polarity."

Technical Summary

"The regulation of Epithelial cell polarity specification and maintenance is a key problem in cell biology. The vast majority of cancers in human originate from epithelia (i.e. Breast, Colon, Lung, Kidney etc.) and a major hallmark of tumourogenesis is a progressive loss of epithelial cell polarity. This eventually leads to Epithelial to Mesenchymal (EMT) cell transition a key step toward cell metastasis activity. Epithelial cell specification presents the converse step (i.e. Mesenchymal to Epithelial transition, MET). Better understanding the molecular mechanisms and signalling pathways required for promoting MET is therefore a key step toward a better understanding of EMT.||To tackle this question in vivo, we are using the genetically amenable Drosophila melanogaster. While up to 80% of the genes associated with diseases in human, are conserved in Drosophila, they are often present as one single locus, which is ideal as very little redundancy is present. So far this approach has allowed us to characterize the function of the conserved tumour suppressor PTEN, during epithelial apical membrane morphogenesis. PTEN is mutated in more than 50% of cancers in human. In epithelial cells, PTEN is recruited at the developing zonula adherens (za) through direct binding to the conserved polarity gene Par3/Baz. Our work in Drosophila has now been confirmed and validated in mammalian epithelial cells, by two other independent groups. Since then, we have tried to better characterize the PTEN/Par3 interface and in particular we have focussed our work on the problem of za morphogenesis and maintenance. The za is the principal membrane domain for the cells to form an epithelial sheet, as this domain is responsible for cell-cell anchorage. We believe that we have now solved a number of key open questions in this field of research. In particular, we have recently solved the molecular basis for Par3 requirement during za assembly in epithelial cells. Par3 and PTEN are also key genes for directed cell migration and we propose that in pathological conditions such as cancer, defect in their regulation in epithelial cells (i.e. phosphorylations/localization), and are likely to have a profound impact toward cell metastasis."
 
Description BBSRC Alert16 - Lattice sheet microscope
Amount £569,000 (GBP)
Funding ID BB/R000697/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2017 
End 08/2018
 
Description Multi-user equipment grant
Amount £290,000 (GBP)
Funding ID 108427/z/15/z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2014 
End 09/2019
 
Title Optimising Lattice sheet microscopy 
Description developing new approaches to low photo-toxicity microscopy. 
Type Of Material Technology assay or reagent 
Year Produced 2018 
Provided To Others? No  
Impact Panned grant applications. 
 
Description Ect2- Cdc42 and Mitotic rounding 
Organisation University College London
Department MRC Laboratory for Molecular Cell Biology (LMCB)
Country United Kingdom 
Sector Academic/University 
PI Contribution We have provided biochemical evidence that the GEF Ect2 binds to Par6 and Cdc42 in Drosophila
Collaborator Contribution The Baum lab has identified a major role for Ect-2 during mitotic cell rounding and remodelling of epithelial polarity in this particular context.
Impact Ect2/Pbl Acts via Rho and Polarity Proteins to Direct the Assembly of an Isotropic Actomyosin Cortex upon Mitotic Entry André Rosa, Evi Vlassaks, Franck Pichaud, Buzz Baum Dev Cell. 2015 March 9; 32(5): 604-616. doi: 10.1016/j.devcel.2015.01.012 PMCID: PMC4359025
Start Year 2014
 
Description Mechanical forces involved in neuroepithelial morphogenesis 
Organisation University College London
Department MRC Laboratory for Molecular Cell Biology (LMCB)
Country United Kingdom 
Sector Academic/University 
PI Contribution Live imaging of developing retina - systematic study of the forces at play during neuro-epithelial morphogenesis including asymmetric cell division.
Collaborator Contribution The Mao (LMCB) lab is helping us with in silica models of ommatidial cell patterning during retinal development. The Banerjee (UCL, IPLS/FLS) lab is helping us with PIV analysis of Myosin activity in ommatidial cells during ommatidial patterning
Impact paper
Start Year 2014
 
Description Mechanisms of actomyosin force regulation during epithelial tissue patterning 
Organisation University College London
Department Institute for the Physics of Living Systems
Country Unknown 
Sector Academic/University 
PI Contribution Using the developing fly retina as a model system to study sensory epithelium patterning.
Collaborator Contribution Shila Barnerjee (UCL- IPLS) and Yanlan Mao (UCL-MRC LMCB/IPLS) are providing us with expertise on how to analyse Myosin2 during multicellular patterning.
Impact Research paper in preparation. Joint grant submission to follow up on our work (BBSRC)
Start Year 2017
 
Description Mechanisms of neuronal polarity 
Organisation University College London
Country United Kingdom 
Sector Academic/University 
PI Contribution We discovered that nuclear export of polarity factors direct cortical neuron polarity
Collaborator Contribution The Riccio lab helped us with in vivo work on the nuclear export pathway during neuronal polarity.
Impact We have now published our work showing that cortical neuron polarity is initiated by the nuclear export of the polarity protein LKB1 (Mencarelli et al., 2016- Cell repports). We are now preparating a follow up manuscript that report that nuclear export of LKB1 is also a key step during directed migration of neural crest cells during development.
Start Year 2017
 
Description Regulation of Cdc42 in epithelial cells 
Organisation University College London
Department Institute of Ophthalmology UCL
Country United Kingdom 
Sector Academic/University 
PI Contribution Discovery that RhoGap19D regulates Cdc42 during epithelial apical membrane differentiation
Collaborator Contribution Matter lab: Expanding our finding to mammalian cell cultures (Caco cells)
Impact Paper published on 2017 : An apical MRCK-driven morphogenetic pathway controls epithelial polarity. Zihni C, Vlassaks E, Terry S, Carlton J, Leung TKC, Olson M, Pichaud F, Balda MS, Matter K. Nat Cell Biol. 2017 Sep;19(9):1049-1060. doi: 10.1038/ncb3592. Epub 2017 Aug 21.
Start Year 2014
 
Description Role of Pak4 during epithelial membrane differentiation 
Organisation Memorial Sloan Kettering Cancer Center
Department Cell Biology Program
Country United States 
Sector Academic/University 
PI Contribution Discovery that Drosophila pak4 is regulates the epithelial polarity gene network.
Collaborator Contribution Identification of the epithelial protein Par6 as a substrate for Pak4
Impact This collaboration has consisted in capitalising on Drosophila genetics to determine exactly where Pak4 fits in the existing network of epithelial polarity genes. In my lab, this has meant establishing and studying the relevant Par6 and Pak4 transgenic animals. Corresponding paper submitted Oct 2015
Start Year 2014
 
Description Role of RhoGAP19D and Ect2 during epithelial polarity remodelling 
Organisation University College London
Department Institute of Ophthalmology UCL
Country United Kingdom 
Sector Academic/University 
PI Contribution Characterisation of the role of RhoGAP19D and Ect2 during epithelial polarity remodelling in vivo. This includes generating novel mutants for RhoGAP19D has none existed prior to our work
Collaborator Contribution The lab of Karl Matter is providing us with expertise on vertebrate cell culture. This lab is examining the function of the RhoGAP19D ortholog that we have identified in MDCK cells. In Parallel, we realised that part of our work on Ect2 was highly relevant for another project at the MRC-LMCB. This initiated a collaboration with the lab of Buzz Baum which led to a publication in 2015.
Impact We have generated a mutant in the RhoGAP19D locus that we are using to characterise the function of this particular Cdc42 GEF during epithelial cell polarity remodelling. This collaboration allows us to examine this function in Drosophila (in vivo) and vertebrates (in vitro). Ect2/Pbl Acts via Rho and Polarity Proteins to Direct the Assembly of an Isotropic Actomyosin Cortex upon Mitotic Entry André Rosa, Evi Vlassaks, Franck Pichaud, Buzz Baum Dev Cell. 2015 March 9; 32(5): 604-616. doi: 10.1016/j.devcel.2015.01.012 PMCID: PMC4359025
Start Year 2013
 
Description Super Resolution imaging 
Organisation National Physical Laboratory
Country United Kingdom 
Sector Academic/University 
PI Contribution Working together with NPL toward establishing a regional user platform for super resolution imaging.
Collaborator Contribution NPL assembles experimental super resolution system.
Impact The setting up of a core facility for super resolution at UCL is now well underway.
Start Year 2011
 
Description Transcriptomic analysis of retinal development 
Organisation Catholic University of Louvain
Country Belgium 
Sector Academic/University 
PI Contribution Expertise with analysing particular genotype in the developing drosophila retina.
Collaborator Contribution Have conducted an extensive survey of the genes whose transcription is regulated during retinal development in Drosophila.
Impact MS in preparation to be published in 2016
Start Year 2013
 
Description MRC blog featuring research in my lab 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact wrote a blog in collaboration with the MRC.
Year(s) Of Engagement Activity 2018
URL https://www.insight.mrc.ac.uk/
 
Description Tweeter feed - Cell polarity@pichaud lab 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Tweeter feed to promote our work on epithelial cell polarity.
Year(s) Of Engagement Activity 2016
URL https://twitter.com/PichaudLab