BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Jamie: "\;A biomechanical switch regulates the transition towa rds homeostasis in oesophageal epithelium"\; Ben: "\;Integrati ng pattern formation and cell movements in our understanding of morphogene sis"\; - Ben Steventon\, Jamie McGinn DTSTART:20211108T143000Z DTEND:20211108T153000Z UID:TALK162514@talks.cam.ac.uk CONTACT:102601 DESCRIPTION:*Jamie McGinn*\nMounting evidence suggests that epithelial ste m cells are more dynamic than originally thought. Stem cell behaviour is n ot a discrete state as it can be re-gained by differentiating cells as a r esult of tissue challenges such as injury and tumorigenesis. This plastici ty may explain why\, despite decades of intensive research in epithelial s tem cell biology\, the field still debates about the identity of the cell populations contributing to the homeostasis and repair of squamous tissues . In order to fully unveil the rules governing epithelial cell behaviour\, it is critical to understand the dynamic nature of epithelial cells by ex ploring their response to situations away from homeostasis. In this study we investigate the cell fate transitions taking place in the mouse squamou s oesophageal epithelium from birth until the onset of adult homeostasis\, as a physiological model of rapid but restricted tissue growth. Observati ons throughout post-natal development show that oesophageal expansion afte r birth occurs in a biphasic pattern\, with a fast initial growth that slo ws down before reaching adult tissue size. This turning point is character ized by a range of changes in the expression of key developmental factors\ , defining the transition of cell fate identity in the basal progenitor ce ll compartment. The establishment of homeostatic oesophageal features coin cide with significant changes in tissue architecture\, including tissue st rain and decreased cell density. Remarkably\, tissue stretching experiment s reveal that the mechanical changes experienced by the developing oesopha geal epithelium after birth are critical for shifting the rapid growing ti ssue into a homeostatic mode. \n\n*Ben Steventon*\nAs cells proceed throug h development\, information contained in the genome is expressed in a cont ext-dependent manner. This must be regulated precisely in both space and t ime to generate patterns of gene expression that set-up the spatial coordi nates of tissue and organ primordia that build the embryo. Our current und erstanding of pattern formation relies on the concept of positional inform ation\, the idea that cells receive instructive signals that impart a spat ial coordinate system to generate pattern. While this model works very wel l in static cell populations with minimal cell rearrangement\, it becomes challenging when considering dynamic morphogenetic processes such as gastr ulation. Furthermore\, pattern formation in gastrulation is highly flexibl e to alterations in the size\, scale and spatial rearrangement of cells in both experimental and evolutionary situations. \nOur work seeks to provi de illustrations of two concepts that will help resolve these long-standin g problems of pattern regulation\, evolvability and self-organisation. Fir stly\, downward causation emphasises the role that multi-tissue interactio ns play in relaying information from changes at the organ and organism lev el to the regulation of gene regulatory networks (GRNs) at the cell level. Secondly\, pattern emergence considers how extracellular signals act to c ontrol the dynamics of autonomous GRN activity\, rather than as instructiv e signals to direct cell fate transitions. In this sense\, we propose that pattern formation should not be seen as a downstream output of organisers and their responding tissues\, but rather as an emergent property of thei r dynamic interaction. LOCATION:Online END:VEVENT END:VCALENDAR