Supplementary Figure 4: Most micronuclei disassemble their nuclear envelopes with normal kinetics during mitotic entry.

a) Experimental schematic for nuclear envelope breakdown assay using Xenopus egg extracts, which contain abundant kinases whose activity can disassemble typical nuclear membranes and promote chromosome condensation, the latter visualized by H2B–mRFP. b) Time-lapse imaging of semi-permeabilized RPE-1 cells expressing lamin A–GFP and H2B–mRFP following the addition of interphase or CSF-arrested egg extracts. Scale bar, 5 µm. c) Lamin A–GFP disassembly kinetics following the addition of interphase or CSF-arrested egg extract (mean ± SEM). d-e) Lamin A–GFP disassembly kinetics following CSF-arrested egg extract addition for d) primary nuclei and e) micronuclei. Inset depicts the overlay between primary nuclei and micronuclei with normal disassembly. Green lines represent mean ± SEM, and red lines indicate individual examples of micronuclei with partial or delayed lamin A–GFP disassembly. f) Example image series of a micronucleus that fails to efficiently disassemble its nuclear envelope upon addition of CSF-arrested egg extracts. Scale bar, 2 µm. g) Quantification of the frequency of micronuclei undergoing normal or delayed disassembly in the presence of CSF-arrested egg extracts. Data in c–e and g represent n = number of nuclei or micronuclei as indicated.