BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:"\;Single-cell morphometrics reveals ancestral principles of n otochord development"\; - Toby Andrews\, Department of Zoology\, Unive risty of Cambridge DTSTART:20210607T133000Z DTEND:20210607T143000Z UID:TALK161002@talks.cam.ac.uk CONTACT:Elena Scarpa DESCRIPTION:Embryonic tissues are sculpted by the dynamic behaviours of th eir constituent cells. In turn\, evolutionary transitions in form arise fr om tweaks in those behaviours. To define how evolution acts on development al programmes\, new methods are needed to map out morphogenesis across a d iversity of organisms\, including non-model systems where experimental tra ction is limited. Here\, we have applied a quantitative approach to define how the notochord forms during the development of amphioxus - a basally-b ranching chordate\, used to infer ancestral properties in the phylum. Usin g a single-cell morphometrics pipeline\, we quantify the geometries of tho usands of amphioxus notochord cells\, and project them into a morphospace\ , in which they organise into branching trajectories of cell shape change. Focussing on a single region\, we first define stepwise cell shape transi tions that enforce a constant rate of tissue elongation in the notochord. Within this\, we use mathematical modelling to predict a synergistic relat ionship between intercalation and growth in generating length. By spatiall y mapping trajectories\, we go on to identify conspicuous regional variati on\, both in developmental timing and trajectory topology. Finally\, we sh ow experimentally that posterior cell division modulates notochord length by regulating the number of cells entering each shape trajectory. Our appr oach offers a new way of seeing in the study of tissue morphogenesis\, tha t enables holistic analysis of cell behaviours defining tissue geometry. I t also reveals an unexpectedly complex scheme of notochord morphogenesis t hat might have operated in the first chordates. LOCATION:Online END:VEVENT END:VCALENDAR