Cell fixation for imaging
Cells were fixed in a final concentration of 4% paraformaldehyde in 10 mM Tris-HCl buffer, pH 7.4 (stock: 16% paraformaldehyde solution in distilled water, EM grade, 15710, Electron Microscopy Science) for 10-30 minutes at room temperature. They were then washed repeatedly in PBS to reduce the background autofluorescence, before staining with DAPI (4′,6-diamidino-2-phenylindole) at final concentration 50 ng ml-1 for 10 minutes for nuclear staining, and/or staining with antibodies for immunofluorescence. Images were captured by using a Carl Zeiss Microscope stand Axio Observer 7 system or Marianas Yokogawa-type spinning disc inverted confocal microscope.