the invitation

Invitation to Seminar Talk
Regulation of actomyosin contractility in-vivo:
lessons from C. elegans
Ronen Zaidel-Bar
National University of Singapore
Host: Carl-Philipp Heisenberg
Actin and non-muscle myosin II filaments together form contractile structures that support cell and
tissue structure and drive essential dynamic processes, such as cell division, migration, and
morphogenesis. Actomyosin contractility in non-muscle cells is tightly regulated in space and time
by a network of proteins, including RhoGTPases, kinases and actin binding proteins, collectively
termed the Contractome. We are using C. elegans as a model to study the contractome in vivo.
In my talk I will present two stories that illuminate different aspects of actomyosin contractility
regulation: one at the level of Rho GTPase activity and the second at the level of actin bundle
organization. The C. elegans spermatheca, an epithelial pouch, is the site of oocyte fertilization, and
embryo exit from the spermatheca is accomplished by actomyosin-dependent spermatheca
contraction. We found this contraction to depend on RHO-1 activity level, which is regulated by the
RhoGAP SPV-1 and the RhoGEF RHGF-1. Importantly, we found both SPV-1 and RHGF-1 localization
to the membrane to be responsive to membrane stretching and we further elucidated the molecular
mechanism for this mechanobiological feedback loop controlling contractility.
In the C. elegans zygote cortical contractility drives polarization and cytokinesis and affects other
cellular processes, such as spindle positioning. We characterized a mutant in the actin bundling
protein plastin (a.k.a. fimbrin) and found profound attenuation of cortical contractility. Quantitative
analysis of cortical dynamics revealed a defect in long range coordination and force transmission in
the cortical network. Thus our work highlights the importance of actin bundling for micron scale
actomyosin network architecture and cell scale contractile events such as polarization and
cytokinesis.
Tuesday, March 29, 2016, 10:00am
Seminar room Mondi 2, Central Building, 1st Floor
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