A caspase–RhoGEF axis contributes to the cell size threshold for apoptotic death in developing Caenorhabditis elegans
Fig 2
ced-3 caspase cooperates with ect-2 RhoGEF in the control of daughter cell sizes in the NSM lineage.
(A) Schematic representation of the NSM lineage. The NSMsc and NSM can be identified in comma stage embryos using the transgene Ppie-1::mCherry::PHPLCΔ (ltIs44), which labels the plasma membrane of cells (orange arrow indicates the NSMsc and blue arrow indicates the NSM). Using confocal imaging, a Z-stack of the NSMsc and NSM can be obtained immediately post-division and the size ratio of the NSMsc:NSM can be estimated. The Z-stack of a pair of NSMsc (orange) and NSM (blue) in +/+, ect-2(ax751ts) and ect-2(xs111gf) mutants is shown. The corresponding mean daughter cell size ratios (NSMsc:NSM) are given below. Scale bars: 10 μm and 2 μm. (B–D) Daughter cell size ratios in +/+ and various ect-2 and ced-3 single and double mutants measured using ltIs44 (n = 10–20). Each gray dot represents the daughter cell size ratio of 1 pair of daughter cells. Horizontal red lines represent mean values, which are also indicated on top. The horizontal red dotted line represents the mean daughter cell size ratio of wild-type (+/+) embryos for comparison. The horizontal black dotted line in Fig 2B and 2C represents a daughter cell size ratio of 1.0 indicating equal division. The horizontal black dotted line in Fig 2D represents a daughter cell size ratio of 0.5 indicating that the smaller daughter is twice as small as the larger daughter. Statistical significance was determined using the Dunnett’s T3 multiple comparisons test (**** = P < 0.0001, ** = P < 0.01, * = P < 0.05, ns = P > 0.05). NSM, neurosecretory motor neuron.