Figure 3. Micronuclei frequently lack lamin B1 in the nuclear envelope.

(a) Schematic depiction of marker proteins with nuclear localization (red) and cytoplasmic localization (green) after nuclear envelope rupture. (b) Localization of NLS-RFP and CLS-GFP in untreated cells (untr), cells treated with 48 hr of colchicine (colch) and 48 hr of colchicine followed by 30 min of cytochalasin B (colch+DCB) and (c) in isolated MN. (d) Immunofluorescence staining of A9 nuclei and MN with lamin A/C and lamin B1 antibody. The lamin B1 negative MN is highlighted by the yellow arrowhead and the lamin B1 positive MN is indicated by red arrowhead. DNA was stained with DyeCycle Green. (e) Quantification of primary nuclei (PN) and MN positive and negative for lamin A/C and lamin B1. All plots show mean ± s.e.m. of three independent experiments; at least 400 nuclei were scored in each experiment. (f) The diameters of lamin B1 negative (-) and positive (+) MN are visualized. Each dot represents the diameter of one MN. The medians are highlighted in red. Three independent experiments, N = 304. Mann Whitney test, p=0.00012. (g) The diameters of lamin B1 negative (-) and positive (+) MN spontaneously arising in RPE1 cells are plotted. Each dot represents the diameter of one MN. The medians are in red. N = 45. Mann Whitney test, ****p<0.0001. Scale bar: 10 μm in all images.