Egg Helps To Rejuvenate Sperm
Unlike women, a man’s fertile life can extend into the 6th, 7th or even 8th decade. This is because of the different manner in which male gametes (sperm) and female gametes (eggs) are produced. Women are born with all the eggs they will ever have, and, once a month beginning at puberty, one egg is matured and ovulated. Sperm are produced more or less continuously: a spermatogonial cell is recruited from the self-renewing germinal stem cell population and undergoes mitotic and meiotic cell divisions that result in up to 256 sperm arising from that single original cell. Chromosome abnormalities in the fetus are mainly associated with the age of the mother, but not necessarily associated with the age of the father at conception. One explanation for this is revealed in a recent Swedish study which showed that the egg can "reset" the age of sperm. This discovery may play an important role in future stem cell research.
Each time a cell divides, the genetic material at the ends of the chromosomes (telomeres) becomes shorter. Though they are written in the 'alphabet' of the genes, telomeres do not contain the codes for proteins. Instead these repetitive sequences protect the ends of the chromosome from damage, and prevent the chromosomes from fusing into rings, or binding haphazardly to other DNA in the cell nucleus. This is important for the genetic stability of the cell. Cells stop dividing and die when telomeres become too short. Hence, telomeres act as a DNA clock that can indicate the age of a cell. The researchers discovered that the egg cell can cause the telomeres of a fertilizing sperm cell to become longer. This ability would certainly be a benefit chromosomes contained in sperm arising from stem cells that had undergone multiple self-renewal divisions.
"We are the first to show that egg cells have the ability to rejuvenate other cells, and this is an important result for future stem cell research", says Associate Professor Tomas Simonsson, who leads the research group at the Sahlgrenska Academy that has made this discovery.
Each time a cell divides, the genetic material at the ends of the chromosomes (telomeres) becomes shorter. Though they are written in the 'alphabet' of the genes, telomeres do not contain the codes for proteins. Instead these repetitive sequences protect the ends of the chromosome from damage, and prevent the chromosomes from fusing into rings, or binding haphazardly to other DNA in the cell nucleus. This is important for the genetic stability of the cell. Cells stop dividing and die when telomeres become too short. Hence, telomeres act as a DNA clock that can indicate the age of a cell. The researchers discovered that the egg cell can cause the telomeres of a fertilizing sperm cell to become longer. This ability would certainly be a benefit chromosomes contained in sperm arising from stem cells that had undergone multiple self-renewal divisions.
"We are the first to show that egg cells have the ability to rejuvenate other cells, and this is an important result for future stem cell research", says Associate Professor Tomas Simonsson, who leads the research group at the Sahlgrenska Academy that has made this discovery.
posted by Kathleen, Contributing Editor at
1:30 PM
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