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SUMMARY:Mechanics and Evolution of Cell Sheet Folding – Embryonic Invers
 ion in the micro-alga Volvox - Stephanie Höhn (University of Cambridge)
DTSTART:20180502T120000Z
DTEND:20180502T130000Z
UID:TALK104362@talks.cam.ac.uk
CONTACT:Olivia Tidswell
DESCRIPTION:Cell sheet folding is an essential process during multi-cellul
 ar development\, examples including gastrulation\, neurulation and organog
 enesis. In spite of significant progress in understanding the molecular co
 mponents that drive local cellular changes it is still poorly understood h
 ow these translate into global deformations of cell sheets.  \nThe so call
 ed inversion process in the multicellular green micro-alga Volvox is a pow
 erful emerging model for studying the biomechanical mechanisms underlying 
 cell sheet deformations. During inversion the spherical Volvox embryos und
 ergo invagination and eventually turn themselves inside-out. Different typ
 es of cell sheet deformations have evolved in different Volvox species and
  are associated with different environmental conditions as well as physica
 l constraints. \nA combination of light sheet fluorescence microscopy and 
 mathematical modelling revealed that equatorial invagination during type B
  inversion has to be complemented by active contraction and expansion in t
 he posterior and anterior hemisphere\, respectively. While inversion is ac
 hieved by a single wave of cell-wedging in some species\, in others the an
 terior hemisphere is pulled over an inflection point by contraction rather
  than bending of the cell sheet. This suggests a transition towards a high
 er complexity of embryonic development within the family Volvocaceae. Ongo
 ing laser ablation experiments will elucidate how spatial and temporal dif
 ferences in tensile forces relate to differences in global deformations. T
 hese comparative studies shed light on the interaction of mechanical const
 raints and environmental cues in the context of evolving morphogenesis.
LOCATION:Part II Lecture Theatre\, Department of Zoology
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