Abstract: Most of our tissue and organs are composed of cells that adhere to each other to form epithelial sheets and tubes that act as a barriers between our insides and the outside world. In order to form these sheets, all of the cells must first polarise in the same direction, with their apical surfaces facing outside and their lateral sides forming specialised junctions. More than 80% of tumours arise from epithelial tissues and one of their hallmarks is that the tumour cells lose their apical-basal polarity. Work over the past 20 years has defined a conserved set of polarity factors that define the apical and baso-lateral domains of epithelial cells, but how these are related to cancer formation is currently unknown. I will discuss the canonical model of epithelial polarity and describe a new component of this system that may explain how polarity is disrupted in some cancers. I will then discuss evidence that suggests that one reason why progress has been slow is because different epithelia polarise by distinct mechanisms.

Biography: Daniel St Johnston did his Ph. D. at Harvard, where he cloned the dorsal-ventral patterning gene decapentaplegic. He then spent three years as a postdoc with Christiane Nüsslein-Volhard at the Max Planck Institute in Tübingen, before moving to the Wellcome /Cancer Research UK Gurdon Institute at the University of Cambridge, where he is now a Wellcome Principal Research Fellow and Professor of Developmental Genetics. He is a member of EMBO (1997), a Fellow of the Royal Society (2005) and the Academy of Medical Sciences (2004) and was awarded the EMBO Gold Medal in 2000. He spent his early career analysing the first asymmetries in development that polarize the body axes in Drosophila. This has led him to investigate how cells become polarised, how polarity controls the organisation of the cytoskeleton and how the polarised cytoskeleton is used to target components to the correct place in the cell. Much of his current work uses advanced imaging approaches and genetics to study the development of apical-basal polarity in epithelial cells with the aim of understanding how cortical polarity factors control spindle orientation, polarized secretion and the positioning of intercellular junctions in absorptive and secretory epithelia.