Contractility of the non-muscle and smooth muscle cells that comprise biological tubing is regulated by the Rho-ROCK and calcium signaling pathways. Although many molecular details about these signaling pathways are known, less is known about how they are coordinated spatiotemporally in biological tubes. The spermatheca of the C. elegans reproductive system enables study of the signaling pathways regulating actomyosin contractility in live adult animals. The RhoGAP SPV-1 was previously identified as a negative regulator of RHO-1/Rho and spermathecal contractility. Here, we uncover a role for SPV-1 as a key regulator of calcium signaling.
spv-1 mutants expressing the calcium indicator GCaMP in the spermatheca exhibit premature calcium release, elevated calcium levels, and disrupted spatial regulation of calcium signaling during spermathecal contraction. Although RHO-1 is required for spermathecal contractility, RHO-1 does not play a significant role in regulating calcium. In contrast, activation of CDC-42 recapitulates many aspects of
spv-1 mutant calcium signaling. Depletion of
cdc-42 by RNAi does not suppress the premature or elevated calcium signal seen in
spv-1 mutants, suggesting other targets remain to be identified. Our results suggest SPV-1 works through both the Rho-ROCK and calcium signaling pathways to coordinate cellular contractility. Movie S1 Movie S1 GCaMP embryo transit movies and time series display calcium signaling differences in
spv-1 mutants. Processed GCaMP embryo transit movies are shown in the bottom panels, while time series are simultaneously displayed in the top panels. A wildtype movie and time series are shown in the left column, while a
spv-1 mutant movie and time series are shown in the right column. Metric annotations appear in the time series as they occur in the movies. Both movies and time series were temporally aligned to put oocyte entry at 50 seconds. Movie S2 Movie S2 Kymograms display the spatiotemporal differences in
spv-1 mutant calcium signaling. Processed GCaMP embryo transit movies, the same shown in Movie 1, are shown in the top panels, while kymograms are simultaneously displayed in the lower panels. A wildtype movie and kymogram are shown in the left column, while a
spv-1 mutant movie and kymogram are shown in the right column. Metrics appear on the kymograms as they occur in the movies. Both movies and kymograms were temporally aligned to put oocyte entry at 50 seconds.