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Affiliations: Affiliate Member, Hanson Institute.
Qualifications: B.Sc. (Adelaide), PhD (Adelaide)
Experience:
Lab Members
The main focus of my laboratory is to elucidate the signalling pathways that transform a non-migratory, non-invasive epithelial cell into a migratory invasive mesenchymal cell. The need for cells to move away from their tissue of derivation and take up residence in a new environment where they can proliferate and undergo further differentiation underpins the development of new tissues and organs during embryonal development. In the adult, it also underlies the process of wound healing and is a prerequisite for pathologies such as cancer progression and fibrotic kidney disease. Epithelial cells that make up many tissues and organs are characterised by strong adhesion to adjacent cells that render them quiescent and non-migratory. Cell-cell adhesion is mediated by the homophilic cell-cell adhesion receptor E-cadherin. In contrast, fibroblasts or mesenchymal cells do not express E-cadherin and are isolated cells that have the capacity to migrate and invade their surrounding matrix. Thus for epithelial cells in a tissue mass to migrate they must undergo a drastic morphological and functional transformation, the epithelial-mesenchymal transition (EMT), into a mesenchymal cell. EMT in development is induced in response to a number of growth factors and extracellular signals that regulate development. The signalling mechanisms that regulate such a complex phenomenon is likely to be complex themselves but a common point of convergence of all the pathways is the induction of the transcriptional repressor Snail.
Snail switches off the expression of E-cadherin, a molecule that is the backbone of adhesion between epithelial cells, and switches on, either directly or indirectly, the expression of genes essential for migration. However, little is known of the signalling intermediates that lead to the increase in Snail expression. Do all the extracellular signals that trigger an EMT do so through common intermediates or are there specific intermediates for each pathway? Many of the signals that induce an EMT are also the ones that regulate cell fate decisions in development in which Snail plays no role – how then do downstream effectors differ to give rise to different outcomes? Understanding these mechanisms can also help us elucidate how diseases involving aberrant EMTs might have arisen. Recent work from my laboratory has identified a novel regulator of EMT, the protein tyrosine phosphatase Pez. Pez induces an EMT when overexpressed in cultured epithelial cells with the induction of Snail expression and consequent loss of E-cadherin transcription. We have used the zebrafish (in collaboration with M Lardelli, CMGD and Discipline of Genetics) model to ascertain its role in regulating organ development during embryogenesis. Our data suggest that Pez is an important regulator of EMT in vitro and organ development in vivo. In addition, we have evidence to suggest that it may also play a role in cancer progression and metastatic disease. We are using both in vivo and in vitro models to elucidate the upstream regulators of Pez expression and to identify downstream targets of Pez.
A second area of research in the laboratory is in elucidating the signal transduction pathways evoked in the endothelium during inflammation that enable leukocytes to migrate across the blood vessel wall into the tissue. Neutrophils are the body's first line of defence when an infection occurs. Using an in vitro model of leukocyte transmigration, we have recently demonstrated that activation of the Erk pathway in endothelial cells is essential for altering the barrier properties of the endothelia so that activated neutrophils can transmigrate across it. We have also discovered that activation of endothelial Erk is induced by the release of a soluble factor produced by activated neutrophils. Identification of this neutrophil factor (in collaboration with the Molecular Signalling Laboratory) and its mechanism of action are the current focus in this area of research in the laboratory. Current Projects The laboratory utilises state-of-the-art biochemical
and molecular biological techniques as well as cell-based assays to address
the various biological questions arising. Selected Recent Publications 1. Wadham C, Gamble JR, Vadas MA and
Khew-Goodall Y. The protein tyrosine phosphatase Pez is a major phosphatase
of intercellular junctions and dephosphorylates beta-catenin. Mol.Biol.Cell.
14:2520-2529, 2003. See a PubMed listing of Dr Yeesim Khew-Goodall's publications Funding
Cancer Council of South Australia
1. Identification of downstream effectors of
Pez signalling (i) We have identified a number of genes whose transcription is regulated by Pez overexpression. We will analyse the promoter regions of these genes to identify Pez responsive elements, following transcription factors that bind to the element will be identified. (ii) Use of a ‘substrate trap’ mutant to identify novel substrates. This is based on a technique that we have previously used successfully to identify beta-catenin as a Pez substrate in endothelial cells (1). We will use the ‘substrate trap’ mutant to pull-down potential substrates from epithelial cell lines that we have shown undergo an EMT when Pez is overexpressed.
2. Analysis of Pez mutations identified in colon cancers on its function, expression and localisation. Many molecules that induce an EMT have also been shown
to be instrumental in cancer progression to metastatic disease. We have
observed that Pez expression is highly increased in advanced mammary carcinomas.
Recently, a group in the USA (4) showed
that a number of somatic mutations are present in the Pez gene isolated
from colon carcinoma. We will reproduce these mutations in the human Pez
cDNA and transfect them into human cell lines. We will analyse levels
of expression of the mutants compared to wild-type Pez, as well as their
localisation as Pez may perform different functions depending on its localisation.
We will also examine whether the mutant forms induce an EMT more readily
or whether they alter the proliferative and survival capacity of the cells. 4. Wang Z, Shen D, Parsons DW et
al. Mutational analysis of the tyrosine phosphatome in colorectal cancers.
Science 304:1164-1166, 2004.
All current research projects listed above are available
for both honours and postgraduate students
Lecture Notes Cell and Developmental Biology III: Cell Migration
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Dr.
Yeesim Khew-Goodall
