Regulation of actomyosin contractility in the C. elegans spermatheca

The C. elegans spermatheca is an accordion-like epithelial tube made of 24 cells, in which fertilization takes place. An oocyte comes in from the gonad side, gets fertilized by sperm that is stored in the spermatheca (hence its name!), and then exists into the uterus as a one cell embryo.You can watch the process of ovulation in this movie:

The spematheca can be found in one of two conformation: collapsed, when it is empty, or stretched, when an oocyte is inside. The relaxed spermatheca expands due to the oocyte being pushed inside and it constricts due to actomyosin contractility.

(images by Limor Broday and Irina Kolotuev, taken from WormAtlas)

The spermatheca cells are known to have actin bundles organized in a circumferential orientation, but how actomyosin contraction is regulated in a cyclical manner is unknown and is the subject of research in our lab.

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We have identified SPV-1, an F-BAR and RhoGAP protein as a novel regulator of spermatheca contractility. Interestingly, its localization to the plasma membrane appears to be curvature dependent and we propose that is acts as a mechanosensor, transducing the mechanical signal of membrane stretching into a biochemical signal, i.e. RhoA activity. Such feedback between membrane curvature and regulation of actomyosin contractility could potentially be at play in other cellular processes, such as cell migration, so there is much more to discover.

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We are currently working on the Rho GEFs that activate Rho-1 in the spermatheca and understanding how they are affected by stretching of the spermatheca. We are also collaborating with Erin Cram‘s lab on the interplay between calcium signalling and Rho-1 signalling in the spermatheca.