Meiosis and Longevity in Yeast

Lower forms of life have stages that don't exist in higher animals - such as meiosis in yeast, or the dauer stage in nematodes. Researchers have found they can manipulate longevity by manipulating the molecular machinery associated with these states, but it's generally felt that this is of lesser relevance to mammals. Here is an example of the type: "Human cells have a finite lifespan: They can only divide a certain number of times before they die. However, that lifespan is reset when reproductive cells are formed, which is why the children of a 20-year-old man have the same life expectancy as those of an 80-year-old man. How that resetting occurs in human cells is not known, but MIT biologists have now found a gene that appears to control this process in yeast. Furthermore, by turning on that gene in aged yeast cells, they were able to double their usual lifespan. ... When yeast cells reproduce, they undergo a special type of cell division called meiosis, which produces spores. The MIT team found that the signs of cellular aging disappear at the very end of meiosis. ... The researchers discovered that a gene called NDT80 is activated at the same time that the rejuvenation occurs. When they turned on this gene in aged cells that were not reproducing, the cells lived twice as long as normal. ... In aged cells with activated NDT80, the nucleolar damage was the only age-related change that disappeared. That suggests that nucleolar changes are the primary force behind the aging process." Which is an interesting conclusion, but given all the other evidence for mechanisms of aging in mammals, I'm not sure it's going to translate well into higher animals.



The MIT research is very exciting, and is quite consistent with the views of the late Dr. Bernard Strehler. He thought "the Achilles Heel of the cell" may be the inability to replenish rDNA, the DNA that codes for ribosomal RNA (rRNA). The rDNA consists of repetitive subunits, which "fall off" the end of the array due to mispairing of the two complementary strands. Without rRNA, a cell can't make ANY KIND of protein! Counting the nucleolar-organizing regions in cells is one way to demonstrate this effect. See reference:
Strehler, B.L. (1986). Genetic instability as the primary cause of human aging. Exp. Gerontol. 21, 283-319.
The yeast gene is also called YHR124W.

Posted by: Richard Huemer at April 29th, 2016 2:44 PM

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