As budding yeast undergo meiosis, factors associated with age-induced damage (red) are sequestered into a compartment outside of the newly formed cell membranes (green) and away from the gametes’ genetic material (blue). Image credit: Grant King (CC BY 4.0)
The cells of living organisms accumulate damage as they age. Some of this age-associated damage is found around the organism’s DNA. However, when genetic material is passed on during sexual reproduction, newly born offspring avoid inheriting this age-induced damage. This ensures that the progeny are ‘re-set’ with a fresh lifespan that is independent from their parents’ age.
A lot of what is known about aging has come from studying budding yeast. Yeast cells can undergo a process called meiosis and divide into four cells known as gametes, which are the equivalents of human sperm and egg. During meiosis, the structure that surrounds the cell’s genetic material – known as the nuclear membrane – remains intact, surrounding the DNA as it separates into four distinct parts. As the cell divides, age-associated factors that were originally present in the parent are not inherited by the gametes, but it remains unclear how this occurs.
Now, King, Goodman et al. have investigated this process by attaching fluorescent labels to specific aging factors and tracking how they are distributed inside yeast cells undergoing meiosis. This revealed that age-associated factors were physically sequestered away from the inherited genetic material during meiosis. King, Goodman et al. found that as the nuclear membrane remodeled itself around the genetic material of the four gametes, the damage became confined to a fifth previously unknown membrane-bound compartment. Once outside of the gametes, the aging factors were then selectively destroyed by enzymes released from the parent cell.
All cells age, and many of the mechanisms underlying these processes are similar across species and cell types. A better understanding of how cells age, and of the process by which gametes are able to sequester and eliminate age-induced damage, may help guide efforts to combat aging in other cells.
