A team of Penn State scientists recently discovered a "maternal age effect" which could be indicative of the number of mitochondrial DNA (mtDNA) mutations in maternal egg cells, and the likelihood of transmission of these mutations to babies. Mitochondrial DNA is solely inherited maternally; therefore, any mtDNA mutations the mother accumulates has the potential to affect her baby. These mutations can cause a vast array of devastating diseases and "contribute to others such as diabetes, cancer, Parkinson's disease, and Alzheimer's disease," making the "maternal age affect" of great interest to the field of genetic counseling.
The goal of the team's research was to determine whether maternal age was "important in the accumulation of mtDNA mutations both in the mother and the child as a result of transmission." The researchers took blood and cheek cell samples in women 25 to 59 years-old. Using DNA sequencing, the researchers found more mutations in the older mothers. Greater rates of mutations were also found in children of the older mothers, leading the researchers to hypothesize that a similar mutation process occurs "in the cells of the mothers' bodies and in their germ lines."
The above discovery also guided the researchers to another discovery regarding egg-cell development. While it has been accepted that "developing egg cells go through a 'bottleneck' period that decreases the number of mtDNA molecules," the magnitude of the bottleneck period had not been determined. A large bottleneck would imply that the genetic makeup of the maternal mitochondria would be inherited by the children, and a small bottleneck could result in drastic differences in the genetic makeup of mitochondria between the mother and her child. Through the study, the researchers determined the bottleneck is tiny. This discovery has major implications on genetic counseling, including the ability to predict a percentage range of disease-carrying molecules that will be inherited by the child.
I think the research developed by the Penn State team is extremely important to the field of genetic counseling and family planning. In our current culture, women are starting to have children later in life in order to accomplish career goals and to properly prepare for becoming a mother. However, the decision to procrastinate having children is accompanied by an increased risk for passing down life-altering disorders. While having a baby with Down syndrome is the typical concern for older mothers, genetic counselors can now provide mothers with the probability of having a child with another set of genetic disorders that may be correlated with the mother's age. I think this research could be a gateway for discovering how to reduce the risk of having a child with a chromosomal or mitochondrial disorder in older mothers.
Related article: http://www.pnas.org/content/77/11/6715.full.pdf+html
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