A new study has revealed that there are greater rates of the mitochondrial DNA variants in children born to older mothers, as well as in the mothers themselves, which cause more than 200 diseases and contribute to others such as diabetes, cancer, Parkinson's disease, and Alzheimer's disease.
According to the study, many mitochondrial diseases affect more than one system in the human body, including organs that require a lot of energy, including the heart, skeletal muscle, and brain. They are devastating diseases and there is no cure, so our findings about their transmission are very important.
The discovery of a "maternal age effect" by a team of Penn State scientists that could be used to predict the accumulation of mitochondrial DNA mutations in maternal egg cells-and the transmission of these mutations to children-could provide valuable insights for genetic counseling.
Through DNA sequencing, they found more mutations in blood and cheek cells in the older mothers in the study. Maternal age of study participants ranged from 25 to 59. But finding greater rates of mutations in children born to the older mothers did come as a surprise. The researchers believe a similar mutation process is occurring both in the cells of the mothers' bodies and in their germ lines.
The study led to another important discovery about egg-cell development. Although it was known that developing egg cells go through a "bottleneck" period that decreases the number of mtDNA molecules, scientists didn't know how small or large this bottleneck is. Kateryna Makova, professor of biology and one of the study's primary investigators, said that if the bottleneck is large, the genetic makeup of the mother's mitochondria will be passed to her children.However, if it is tiny-if there is a severe decrease in mitochondrial molecules during the egg-cell development-then the genetic makeup of the child might differ dramatically from that of the mother. What they discovered is that this bottleneck is indeed very small.
The study was published online in the Proceedings of the National Academy of Sciences.
