Contractile non-muscle cells, including smooth muscle and myoepithelial cells, provide the mechanical forces required for tissue homeostasis in numerous organ systems. For example, smooth muscle cells surrounding the vasculature contract in response to increased intraluminal pressure to maintain lumen diameter and blood pressure and myoepithelial cells in the mammary gland provide the contractile force required for milk ejection and to shape the mammary gland mechanical microenvironment. Dysregulation of mechano-perception and force production in these contractile cells contributes to the pathophysiology of numerous diseases ranging from hypertension to breast cancer progression. This highlights the importance of understanding how contractility is regulated and maintained in these mechanically stressed cells throughout animal lifetime. To study this question, we use a component of the C. elegans reproductive system, the spermatheca, as a novel model contractile tube. The spermatheca is composed of 24 myoepithelial cells that encompass the sperm. During ovulation, spermathecal cells are dramatically stretched by the incoming oocyte. The oocyte is immediately fertilized and resides in the spermatheca for a regulated period until coordinated spermathecal cell contractions push the embryo into the uterus. This process occurs 150 times throughout the lifetime of the animal requiring robust regulation of tissue contraction to expel the embryo at the correct time and in the correct direction. In this work, we use live animal imaging to monitor Ca2+ signaling and actomyosin dynamics in spermathecal cells during ovulation. We show that Ca2+ transients are produced only after cell stretch and that Ca2+ signaling is required to initiate actomyosin contraction. We further characterize the role of myosin activity in actomyosin network organization and show that both increased and decreased myosin activity alter network properties including connectivity, orientation, and anisotropy. We conclude that tight spatiotemporal regulation of myosin activity throughout successive rounds of ovulation shapes actomyosin network development and maintenance required for tissue function and animal fertility.
Research And Development
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