Small micronuclei and ruptured nuclei exhibit many similarities. (A) Endogenous cGAS binds DNA in both nuclear blebs (yellow arrows) and many micronuclei (gray arrow). Many micronuclei are γH2AX⁺, and some lack lamin-B (LMNB). (B) Composition of micronuclei assessed after constricted migration shows the following. (Bi) More of the low LMNB micronuclei are γH2AX⁺ and cGAS⁺, expressed as a fraction of the micronuclei counted (Frcn Micronucl.; for 30–40 micronuclei per condition from three experiments; *, P < 0.05). (Bii) A broad distribution of small and large micronuclei (n = 68 from three experiments; *, P < 0.05). Rel. Freq., relative frequency. (C) Small micronuclei (<3 µm) tend to have low KU80 (left two images), low GFP-KU70 (bottom right image), and low LMNB but high cGAS (bar graphs; 30–40 micronuclei per condition from three experiments; *, P < 0.05). For KU80/DNA, intensity normalization (Int. Norm.) is done by normalizing to the main nucleus. All scale bars: 2 µm. (D) Heatmap summary of similarities between nuclear blebs, nuclear aspiration, and micronuclei from various experiments in terms of lamin-B dilution, cGAS entry from cytoplasm, nuclear (Nucl.) pore dilution, and levels of DNA repair factors (as explained in Materials and methods, Heatmap comparisons of curvature-associated nuclear envelope rupture properties). TW, Transwell.