Sensor dynamics in L3 asymmetric and L2 symmetric seam cell divisions.

(A) Schematic overview of divisions in the Vn seam cell lineages (n = 1–4, 6). These seam cells undergo one asymmetric cell division during every larval stage (L1-L4). During these divisions the seam cells produce a posterior self-renewing daughter cell (Vn.p), and an anterior daughter cell that differentiates and fuses with the hyp7 syncytium (Vn.a; orange circles). In the second larval stage (L2), seam cells undergo one additional, symmetric cell division, producing two self-renewing seam daughter cells. (B) Still images and blow-ups from spinning disk confocal fluorescence microscopy time-lapse movies of larvae staged at 24 hours after hatching. From top to bottom, images show seam cells (V3.pap, anterior to the left) before anaphase, during nuclear envelope breakdown at prometaphase, and after anaphase (V3.papa and V3.papp). Note that in the two newly formed daughter cells, nuclear export of the sensor is observed in the anterior daughter cell before it is observed in its posterior sister cell. Scale bar indicates 20 μm. (C) Graph representing the cytoplasmic-to-nuclear ratio (cyt/nuc) of DHB-eGFP in seam cell L3 asymmetric division (n = 5). Anterior cells in orange, posterior cells in blue, average ratio is indicated by a black line. Asterisk indicates the moment where plotted ratios in the anterior cell start to deviate from the ratios in the posterior cell. The arrow indicates the moment where the difference in ratios is statistically significant (t = 44 min after anaphase). Cells are aligned at the moment of anaphase (t = 0). (D) Still images and blow-ups of spinning disk confocal microscopy movies of worms staged at 20 hours after hatching. From top to bottom, images show seam cells (highlighted: V2.p, anterior to the left) before anaphase, during nuclear envelope breakdown at prometaphase, and after division (V2.pa and V2.pp). Note that in the two newly formed daughter cells the rate of nuclear export of the sensor is similar. Anterior to the left, scale bar indicates 20 μm. (E) Graph representing the cyt/nuc ratio of DHB-eGFP in symmetric L2 seam division (n = 3). Anterior cells in orange, posterior cells in blue, average ratio is indicated by a black line. The cells are aligned at the moment of anaphase (t = 0).