Partitioning and Exocytosis of Secretory Granules during Division of PC12 Cells
Figure 7
Dynamics of SGs during late stages of mitosis. PC12 cells were transfected with cDNAs coding for EGFP-tubulin (green) and hCgB-myc-DsRedExpress (red), synchronized and subjected to widefield fluorescence time-lapse microscopy. ((A1) to (E2)) An overview of the progression of a typical double-transfected PC12 cell through mitosis is shown. Images (A1)–(E1) and (A2)–(E2) represent the EGFP-tub and hCgB-myc-DsRedExpress channels, respectively. At the end of metaphase, SGs are homogeneously distributed in the cell ((A1)/(A2)). During anaphase, SGs temporarily accumulate at sites underneath the future cleavage furrow ((B1)/(B2)). During anaphase and telophase SGs gather in the cell midzone ((C1)/(C2) and (D1)/(D2)). At the end of telophase and beginning of cytokinesis SGs accumulate at the base of the intercellular bridge (grouped arrows in (E2)). Please note that the midbody in (E1)/(E2) is out of focus. ((F) to (I)) Tracks of moving SGs colocalise with microtubules. (F) A merged overview of a selected frame from the video sequence is shown. The single channel data for microtubules and SGs is shown in (G) and (H), respectively. Magnifications from the boxed regions in (F), (G), and (H) are shown to illustrate a punctuate structure positive for hCgB-myc-DsRedExpress that was tracked through four consecutive frames ((G1) to (G4), arrow) and whose trajectory overlapped with a spindle microtubule (H1). (I) A summary of the dynamic colocalisation of the tracked SG and the microtubule is shown. Elapsed time is given in minutes m and seconds s. Scale bars, (G1)–(I) 1 μm, and all other images 5 μm. The video sequence from which the presented images were taken is available as Supplementary Materials, Movie SM2.
