Shrinkage of apoptotic cells.

<p>(A) Video sequence of a <i>ced-1(e1735)</i> gonad expressing PGL-1::GFP (green) and a reporter for germ cell membranes (red); strains for the various transgenic reporters used here and elsewhere are listed at the ends of the respective figures legends. The images compare a non-apoptotic cell (labeled 1) with a cell (X) that underwent apoptosis during the recording. At 14 mins and at earlier timepoints the X cell is slightly larger than the non-apoptotic cell, because all germ cells are increasing in size as they move proximally (to the right). Immediately after the 14 min timepoint, PGL-1 diminishes in the X cell and the cell decreases in size. Note that two cells adjacent to, and above, the X cell also undergo apoptosis in the recording. (B) Video sequence of a wild-type gonad expressing a reporter for PGL-1 (red puncta) and a reporter for membranes (also red). Two cells (X1 and X2) underwent apoptosis during the recording, and are compared with two adjacent, non-apoptotic cells (1 and 2). The perimeters of the apoptotic cells and non-apoptotic cells are indicated by solid and dashed outlines, respectively. Both apoptotic cells begin to lose PGL-1 and decrease in size immediately after 28 mins. Note that both apoptotic cells are initially similar in size to the adjacent, non-apoptotic cells (see also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007417#pgen.1007417.s002" target="_blank">S1 Fig</a>). (C) The top row is a video sequence comparing a shrinking apoptotic cell (X) with two non-apoptotic cells (1 and 2). The bottom row shows the same cells combined with a sheath cell reporter (green). The optical plane is 1.5 microns below the outermost germ cell surface, and shows transient protrusions from the sheath cell that extend for short distances between some non-apoptotic germ cells. (D) Orthogonal view of the same gonad shown in panel C, taken through a plane that bisects the ring channel of the apoptotic cell (X). Shrinkage appears to be completed by 22 mins, but the ring channel appears to remain open until at least 26 mins. (E) Video sequence showing an enlarged oogonium (X) undergoing apoptotic shrinkage. The complete video sequence, including sheath cell engulfment, is shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007417#pgen.1007417.s015" target="_blank">S2 Video</a>. (F) Transformed <i>fog-1(q253)</i> mutant male gonad with oogonia, including three, shrunken apoptotic cells (X). The panel at right (F’) shows a 3 micron optical projection of the DNA channel: Engulfed apoptotic cells quickly show significant chromatin compaction, but there is relatively minor compaction in the absence of engulfment, as shown here. We use 3 micron projections where listed throughout this report to accentuate chromatin compaction. Note the high level of F-actin staining (red, phalloidin) in the shrunken apoptotic cells compared to the large, non-apoptotic cells (dashed outline). (G) F-actin staining of non-apoptotic cells. The high magnification in panel G’ indicates fine, cytoplasmic actin filaments extending between the nucleus and plasma membrane (short arrow). The intensity of staining in the cytoplasm is much less than at the cell periphery (long arrow), which is saturated in this image. (H) Comparison of F-actin staining at the perimeter of a non-apoptotic cell (solid arrow), and two apoptotic cells (open arrows) in a <i>ced-1(e1735)</i> gonad. Note that the level of F-actin is higher in the older apoptotic cell (right) than in the younger apoptotic cell (left). Bars = 5 microns. Fluorescent reporters: (A) JJ2100 + OD70, (B) JJ2212 + OD70, (C, D) OD70 + MD701.