Figure 2.

Basal bodies are more prevalent in the deeper cortical plate (CP) at E16.5. E13.5 embryos electroporated with cDNA encoding GFP, killed and fixed for immuno-EM at E16.5. A: DAB immunostaining with anti-GFP antibodies shows GFP⁺ cells (arrows) with leading and trailing processes in both the deeper layer and the upper layer of the CP. B: Higher magnification of the upper CP showing a cell (arrow) with a typical migrating profile. C: Bar graph shows a summary of the position of centrioles/basal bodies that were identified in deeper and upper layers of the CP docked (to the plasma membrane) or undocked. In deep CP, ~70% were docked (mostly in cells that were GFP⁻). In upper CP, most centrioles (~90%) were undocked. D–I: Electron micrographic examples of centrioles and basal bodies in deep (D–G) or upper (H,I) CP. D1: A docked basal body in a GFP⁻ cell (boxed area is shown in D2). GFP immunoprecipitate is visible in the upper left cell (arrow). E: A docked basal body with a small axoneme extension (arrowhead). F1: Another example of a docked basal body in a GFP⁻ cell. The boxed region is shown in F2 and an adjacent section (AS) in F3. G1,3: Adjacent sections of a GFP⁺ cell (arrows point to GFP precipitate) with a leading process. Boxed regions in G1,3 are magnified in G2,4, respectively. H1: A GFP⁺ cell in the upper CP with undocked centrioles (boxed area is magnified in H2, which shows two centrioles (arrowheads). I1: Another example of a GFP⁺ cell in the upper CP. The boxed area in I1 is enlarged in I2, with an adjacent section shown in I3. Scale bars = 50 μm in A; 2 μm in D1,E,F1,G1,H1,I1; 0.5 μm in D2,F2,G2 H2.