In the last two posts I shared photomicrographs of mouse L-1210 cells in various stages of decomposition. The unusual structures generated from nuclei appear to be related to the stage in the cell cycle in which the original cell was in at the time of decomposition. Let me provide models here to illustrate what I think is going on in these photomicrographs. I will do my best to keep this as simple as possible. If you want more detailed information, you can visit the rest of the blog are shoot me an e mail at firstname.lastname@example.org.
What you see in the first picture are small rings attached to a larger ring, the yellow arrow points to a small ring that has an internal hub associated with it. Part of these rings are missing in the bottom of the larger ring, revealing some kind of attachment matrix. In the next two pictures these small rings can be seen detaching from the larger ring, much like grapes falling from a vine. In the last picture can be seen fusions of circles. I believe these phenomena can be explained in the following way:
There is a binary switch here which functions like a computer bit, i.e., off or on (1 or 0). In the case of circles, it is fission or fusion. The circles are either released from the nuclear DNA or they fuse with it. In either case, information is lost making the process irreversible. In the case of fusion, only a small amount of information (DNA) is lost. In the case of fission, an entire circle of DNA is lost. This irreversibility is why scientists have had so many problems with stem cell research. So the next question is this: How do adult salamanders and lizards regenerate limbs and tails? The answer to this is quite simple: There exists a population of precursor cells within these animals that have not undergone differentiation. When a limb is amputated, these cells begin to proliferate and regenerate the limb. Apparently, humans and other animals lack these kinds of cells. So one final paradox remains: How can scientists clone sheep or other animals when these kinds of regenerating cells appear to be lacking? Dolly was cloned from sheep udder cells but the process was very inefficient; out of 277 cell fusions, only one yielded a viable reproductive animal. There are similar problems with adult stem cell research in general. I would hazard to guess that the closer the stem cell is genetically to its desired tissue type, the greater the odds of success. So what about Dolly? How was that possible? Again, I will hazard another guess: There may be some cells lurking about in adult tissues that are capable of regenerating a complete animal, i.e., their DNA has not been “corrupted” by differentiation. Finding those cells (when they exist) is like looking for a needle in a haystack.
The problems associated with stem cell research may lie in something called heterochromatin. Simply put, this is inactive DNA covered by layers of proteins. I suggest that the heterochromatin in different kinds of stem cells inactivates different kinds of DNA. This heterchromatic DNA may still be in pristine condition, i.e. there has been no loss of genetic information. Stem cells that generate red blood cells may have heterochromatic DNA that can be used to generate nerve cells and vice versa. Therefore, the closer genetically the stem cell is to the desired tissue, the better the results. One potential problem with this could occur if the original stem cell DNA is still active in the cloned cell. This could result in a genetic chimera with two active compartments, kind of like fusing mouse and human cells.
The binary model I have discussed here is not limited to cell differentiation as you will find out by visiting other posts and page tabs on this blog. I use this model to explain how cells such as ours evolved from bacteria and viruses and may still do so today. In fact, cancer may result from the way our cells have evolved from more primitive forms of life, including not only viruses and bacteria, but even yeast and more complex forms of life.
Next post: Runaway endosymbionts, what are they?