Figure 1.
Pulsatile medioapical actomyosin dynamics correlate with cell area changes during epithelial remodeling. (A) Left: During remodeling of ommatidia, the 2° LCs narrow and elongate with 3° LCs compact to form alternating corners. Right: Key for cell types. (B) Medioapical actomyosin dynamics in LCs during cell shape changes. Top: Snapshots of a lattice edge. Bottom: Zoomed-in images of F-actin and MyoII. In the first three time points, the cell is contracting (red bar below), and in the last, it is expanding (green bar). F-actin is present in nodes (yellow arrowheads) that are moving and appear to increase during contraction. The nodes form a ring-like structure (red arrowhead) connecting to the cell surface (blue arrowheads). The ring disassembles and remodels during expansion (green arrowhead points to a gap forming in the ring at t15). (B′ and B″) Time-shifted Pearson’s correlation charts (N = 11 cells from three eyes). Solid line, mean R-value at each time shift; Green band, standard error of the mean, here and in subsequent figures. (B′) Medioapical F-actin and MyoII accumulate in synchrony, positively correlating with 0 time lag. (B″) F-actin and cell area negatively correlate, with peak F-actin occurring 15 s before peak contraction. (C) Rok is present and moving in LCs. Top: Snapshots of a lattice edge. Bottom: Zoomed-in views of boxed area. Yellow arrows: Medioapical foci of Rok accumulation. (D) Rho1 is present and moving. Top: Snapshots of a lattice edge. Bottom: Zoomed-in views of F-actin and Rho1 in an LC. Yellow arrows: Foci of Rho1 accumulation. (E–E″) At higher temporal resolution, three behaviors of the medioapical actomyosin network in LCs are discernable (Video 1). (E) Enrichment of medioapical F-actin precedes the assembly of a medioapical ring (red arrowhead). (E′) Movement and fusion of F-actin nodes (yellow arrowheads). (E″) Movement of nodes (yellow arrowheads) and fusion with the junctional actomyosin network (white arrow). (F) Medioapical F-actin pulse frequency in WT 2° LCs is ∼6 min (349 ± 96 s, N = 11 cells from three eyes). (G) On average, medioapical F-actin levels are 1.4-fold higher at their peak than at their trough levels (N = 14 cells from three eyes). Scale bar = 3 µm.

Pulsatile medioapical actomyosin dynamics correlate with cell area changes during epithelial remodeling. (A) Left: During remodeling of ommatidia, the 2° LCs narrow and elongate with 3° LCs compact to form alternating corners. Right: Key for cell types. (B) Medioapical actomyosin dynamics in LCs during cell shape changes. Top: Snapshots of a lattice edge. Bottom: Zoomed-in images of F-actin and MyoII. In the first three time points, the cell is contracting (red bar below), and in the last, it is expanding (green bar). F-actin is present in nodes (yellow arrowheads) that are moving and appear to increase during contraction. The nodes form a ring-like structure (red arrowhead) connecting to the cell surface (blue arrowheads). The ring disassembles and remodels during expansion (green arrowhead points to a gap forming in the ring at t15). (B′ and B″) Time-shifted Pearson’s correlation charts (N = 11 cells from three eyes). Solid line, mean R-value at each time shift; Green band, standard error of the mean, here and in subsequent figures. (B′) Medioapical F-actin and MyoII accumulate in synchrony, positively correlating with 0 time lag. (B″) F-actin and cell area negatively correlate, with peak F-actin occurring 15 s before peak contraction. (C) Rok is present and moving in LCs. Top: Snapshots of a lattice edge. Bottom: Zoomed-in views of boxed area. Yellow arrows: Medioapical foci of Rok accumulation. (D) Rho1 is present and moving. Top: Snapshots of a lattice edge. Bottom: Zoomed-in views of F-actin and Rho1 in an LC. Yellow arrows: Foci of Rho1 accumulation. (E–E″) At higher temporal resolution, three behaviors of the medioapical actomyosin network in LCs are discernable (Video 1). (E) Enrichment of medioapical F-actin precedes the assembly of a medioapical ring (red arrowhead). (E′) Movement and fusion of F-actin nodes (yellow arrowheads). (E″) Movement of nodes (yellow arrowheads) and fusion with the junctional actomyosin network (white arrow). (F) Medioapical F-actin pulse frequency in WT 2° LCs is ∼6 min (349 ± 96 s, N = 11 cells from three eyes). (G) On average, medioapical F-actin levels are 1.4-fold higher at their peak than at their trough levels (N = 14 cells from three eyes). Scale bar = 3 µm.

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