What you see in the picture below looks like some kind of primitive fungal colony, releasing spores. In was in fact derived from a colony of serum-arrested mouse L-1210 cells degrading under a coverslip. The immediate reaction of a tissue culturist would be to pass this off as a fungal infection; a common plague of cultured cells. However, fungal infections are generally anything but subtle. One need not look very hard to find them. Also, typical fungi do not produce the assorted shapes and variety of “cells” you see in this photograph.
At time “zero” one sees only stained mouse cells. Compartmentalization occurs later and can be followed in real time. In fact, you can see “tubules” wriggling right out of the nucleus. It seems reasonable to conclude that such tubules are comprised of actin or similar elements known to be associated with chromatin. Motor proteins must be involved in their generation, as well as pushing the “apoptotic” compartments along a well defined path either within the tubules or at their tips.
What is being seen here appears to be abortive apoptosis, brought about by a localized depletion of elements responsible for the apoptotic cascade. Necrosis and nuclear blebbing can also be seen in other photomicrographs. These two processes seem to have worked together to generate these unusual structures.
Apoptosis is a very sophisticated process that ensures the total destruction of the DNA within dying cells. It is well known that “free” DNA can be deleterious to the health of nearby cells because of its potential to insert itself into the genome and cause massive mutations, similar to viruses. Linear fragments of DNA are usually completely digested when taken up by cells, but circular DNA is another story. It is exonuclease resistant. Still, it can be destroyed by restriction endonucleases which is why viruses have such “fancy” protein coats protecting them prior to genomic DNA insertion. What if the DNA within these mouse L-1210 “compartments” is similarly protected from nuclease degradation? If so, these structures would be much more dangerous than simple, unprotected linear DNA fragments. They may even have the capacity to reinsert themselves within a host cell or to engage in autonomous replication within a cell much like a plasmid or parasitic bacterium. Viewed in this light, apoptosis would be even more important than previously realized. The apoptotic bodies would behave like miniature phagolysosomes destroying invading bacteria.