9/24/2016 ~ This morning I received a worrying and somewhat bewildering email comment on my page about B12 Malabsorption. Ozzyguy011 wrote:
Is this junk science??? Red Blood Cells do not divide… they are formed in the “marrow” of long bones. Because of the lack of nuclei and organelles, mature red blood cells do not contain DNA and cannot synthesize any RNA, and consequently cannot divide and have limited repair capabilities.
If you get such basic science wrong then is the rest of the article any more accurate?
Clearly that made me wonder if somehow I’d gotten it all wrong, and if somehow Dennis Kunkel’s microscopy photo of a red blood cell with a nuclei was some kind of hoax. See photo.
When I googled, “Do red blood cells divide” the first search result quoted Wikipedia, using the exact words that had been used in the email. I’m not sure the email writer had read any further, but I did.
Wikipedia says red blood cells don’t divide:
Because of the lack of nuclei and organelles, mature red blood cells do not contain DNA and cannot synthesize any RNA, and consequently cannot divide and have limited repair capabilities. Kabanova S, Kleinbongard P, Volkmer J, Andrée B, Kelm M, Jax TW (2009). Gene expression analysis of human red blood cells. International Journal of Medical Sciences. PMC 2677714 free to read.
The inability to carry out protein synthesis means that no virus can evolve to target mammalian red blood cells. However, infection with parvoviruses (such as human parvovirus B19) can affect erythroid precursors, as recognized by the presence of giant pronormoblasts with viral particles and inclusion bodies, thus temporarily depleting the blood of reticulocytes and causing anemia.
Parvovirus B12 ~ Read more.
However, earlier on Wikipedia talks about red blood cells and notes “two forms”:
Nucleated red blood cells in mammals consist of two forms: normoblasts, which are normal erythropoietic precurors to mature erythrocytes, and megaloblasts, which are abnormally large precursors that occur in megaloblastic anemias.
Megaloblastic anemia is in fact the condition when red blood cells are too large, having failed to divide properly. Per the above quote it appears that a red blood cell is “nucleated”, meaning it has a nucleus, prior to being “mature”.
Following up on this I found research on how a red blood cell loses its nucleus. The gist of it is that it has long been understood that a red blood cell loses its nucleus when it is mature with the result that it can carry more oxygen which boosts mammal metabolism, but it was unknown exactly how a red blood cell lost/ejected its nucleus.
“Exactly” is the operative word. Basically, it was known that as a mammalian red blood cell nears maturity, a ring of actin filaments contracts and pinches off a segment of the cell that contains the nucleus. As this occurs in red blood cells, macrophages come along and swallow up the discarded nuclei.
Researcher, Harvey Lodish, a professor of biology at Massachusetts Institute of Technology, wrote,
“Using a cell-culture system we were actually able to watch the cells divide, go through hemoglobin synthesis and then lose their nuclei… We discovered that the proteins Rac 1, Rac 2 and mDia2 are involved in building the ring of actin filaments.”
It turns out that red blood cells divide four or five times before losing their nuclei.
How a red blood cell loses its nucleus ~ Read article.
I’m grateful to Ozzyguy011 for bringing his question regarding mature red blood cells no longer having nuclei and no longer dividing to my attention. I’m delighted to be able to send him this web page and reply, “No, it is not junk science. You need to read a little more thoroughly in order to understand what is basically going on. But, thank you for writing.”