Decreased DNA density is a better indicator of a nuclear bleb than lamin B loss.

Nuclear blebs are herniations of the nucleus that occur in diseased nuclei that cause nuclear rupture leading to cellular dysfunction. Chromatin and lamins are two of the major structural components of the nucleus that maintain its shape and function, but their relative roles in nuclear blebbing remain elusive. To determine the composition of nuclear blebs, we compared the immunofluorescence intensity of DNA and lamin B in the main nucleus body to the nuclear bleb across cell types and perturbations. DNA density in the nuclear bleb was consistently decreased to about half of the nuclear body while lamin B levels in the nuclear bleb varied widely. Partial Wave Spectroscopic (PWS) microscopy recapitulated significantly decreased likelihood of high-density domains in the nuclear bleb versus body, independent of lamin B. Time lapse imaging into immunofluorescence reveals that decreased DNA density marks all nuclear blebs while decreased lamin B1 levels only occur in blebs that have recently ruptured. Thus, decreased DNA density is a better marker of a nuclear bleb than lamin B level.