Computer Simulation of Cellular Patterning Within the Drosophila Pupal Eye
Figure 7
Progressive differences between IPCs and OC surface proportions promoted 2° and 3° formation.
(A and B) Graphs showing formation of 2°s (A) and 3°s (B) over time for different size ratios between IPC and OC apical surface areas. Cell death was initiated at 10,000 MCS. The ‘wild-type’ curve indicates 2° and 3° formation when OC apical surfaces expanded but IPCs did not expand during progressive MCS. ‘Wild-type, growing IPCs’ indicates OCs expansion and IPC surface doubling. ‘No Death’ curve indicates expanding OCs with no cell death. ‘No OC Expansion’, No Death' curve indicates constant OC surface area (no expansion) and no cell death. (C) A graph indicating the decrease in cell number for the different simulations. Each line represents the result of a single representative simulation from at least two repetitions. (D) Image capture at 50,000 MCS from a simulation with no OC expansion nor cell death; the pattern fails to resolve; asterisk labels enlarged ommatidium (inset) (E) Three dimensional schematic emphasizing how the vertical movement of nuclei (red arrows) expands the 1°s' surface profiles (blue arrows), in turn laterally ‘crowding’ the neighboring IPCs into a hexagonal pattern. (F, G and H) Reducing OC expansion by expressing smurf introduced patterning errors in vivo. Bars represent 10 µm. (F) Ectopic expression of smurf in paired 1°s led to mild patterning defects, primarily in cell number. (G and H; corresponding tracings in G′ and H′) Reducing growth of single 1°s (marked by GFP) reduced the apical surface profile (E-Cadherin shown in magenta); the neighboring IPC arrangement and 3° cell loci failed to properly resolve. (I and J) Central region of images captured at 0 MCS and 50,000 MCS in simulations in which (I) the entire central OC indicated in red or (J) only half of the OC was prevented from expanding. Arrowheads indicate defects also commonly observed in vivo – missing or ectopic cells. (K) Reduced rst activity (rstCT) led to consistently uneven IPC distribution in 20 hr APR eyes; within this tracing, an example of a rare fused ommatidium is indicated (arrow). Inset: our computer model consistently failed to pattern this rst tracing even after 50,000 MCS The failure to pattern using the same parameters as our wild type tracing indicates that the 20 hr APF rst eye field must already show differences with wild type tissue.