CPE positive endosomes dock at the ingressing cytokinetic furrow during meiosis.

(A) Combined transmitted and fluorescence image of dissected Drosophila cyst; dividing cells chosen for FIB-SEM imaging are boxed. Green, eYFP-Rab7; red, PlyA2-mCherry. Scale bar: 20 μm. (B) 2D section from FIB-SEM reconstruction correlated with “z slice” from confocal. Colors as in A, saturated for ease of visualization. Scale bar: 5 μm. (C) Area boxed in B; FIB-SEM image (top), Rab7 (middle), PlyA2 (bottom). Arrowheads indicate electron-dense endosomes. Scale bar: 2 μm. (D) Volumetric imaging of dividing spermatocytes, showing orthogonal imaging planes, and expected cross sections for LM and FIB-SEM. (E) Fluorescence “z slice” capturing a cleavage furrow in-plane. Scale bar: 4 μm. (F) FIB-SEM image capturing same furrow as in E cross-section, approximated by red lines. Scale bar: 2 μm. (G–I) Correlated fluorescence image, overlay, and rotated FIB-SEM section, respectively, of furrow in-plane. (J) Area boxed in I showing endosomes docked at the furrow (arrow). Scale bar: 1 μm. (J and K) Volume rendering of FIB-SEM 3D reconstruction, with furrow segmented and false colored red, undocked endosomes green, docked endosomes blue. (L) Close-up of K, with furrow segmented translucent and endosomes unsegmented. (M) Matching FIB-SEM section in the imaging plane. Arrows in K, L, M show same endosomes docked at furrow. Scale bar: 2 μm. (N) Independent CLEM/FIB-SEM experiment revealing at higher pixel sampling another example of docked vesicle. Scale bar: 1 μm. CPE, ceramide phosphoethanolamine; LM, light microscopy.