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Topological defects in the nematic order of actin fibres as organization centres of Hydra morphogenesis

TYPEStatistical & Bio Seminar
Speaker:Yonit Maroudas-Sacks
Affiliation:Technion, physics department
Location:Lidow 620
Remark:PhD seminar (student of Kinneret Keren)

Animal morphogenesis arises from the complex interplay between multiple mechanical and biochemical processes with mutual feedback.  Developing an effective, coarse-grained description of morphogenesis is essential for understanding how these processes are coordinated across scales to form robust, functional outcomes. Here we show that the nematic order of the supra-cellular actin fibres in regenerating Hydra defines a slowly-varying field, whose dynamics provide an effective description of the morphogenesis process. We show that topological defects in this field, which are long-lived yet display rich dynamics, act as organization centres with morphological features developing at defect sites. These sites are characterized by a unique mechanical environment, undergoing repeated large, transient and localized deformations. These observations suggest that the nematic orientation field can be considered a “mechanical morphogen” whose dynamics, in conjugation with various biochemical and mechanical signalling processes, result in the robust emergence of functional patterns during morphogenesis.