Father – BioQuakes

Evolving from free-swimming bacteria engulfed by forms of humans’ earliest ancestors billions of years ago, almost every human cell is powered by mitochondria, which use oxygen to create usable energy for our body’s daily needs. Originating from free-floating bacteria, mitochondria have unique DNA different from the 23 pairs of chromosomes in our body. Although our chromosomes come from both parents, 23 each, nearly all humans’ mitochondrial DNA (mtDNA) comes from the mother’s egg. What about the mtDNA in the sperm cell then?

Scientists figure that sperm’s mitochondria are soon broken down by molecular processes after fertilization in other animals, but the reason behind why this happens to humans has been unknown. Now research has found that human sperm’s few mitochondria contain virtually no DNA at all. This mtDNA elimination process might play a role in human infertility and mitochondrial diseases, according to molecular biologist Dmitry Temiakov of Thomas Jefferson University in Philadelphia. Coming up with the same conclusion, Shoukhrat Mitalipov, Ph.D., director of the Center for Embryonic Cell and Gene Therapy at OHSU, said, “We found that each sperm cell does bring 100 or so mitochondria as organelles when it fertilizes an egg, but there is no mtDNA in them.” Using molecular biology, researchers found that sperm’s mitochondria did contain some DNA, along with an important protein called mitochondrial transcription factor A (TFAM) that acts to protect that DNA. But after the sperm cells mature, chemical changes happen which prevent TFAM from entering mitochondria, and as it enters the nucleus instead, it no longer prevents the mtDNA from degrading. The fact that DNA damage in sperm from oxidative stress is common could be another reason why mitochondrial DNA disintegrates. Having mitochondrial DNA doesn’t help fertility either; if the sperm’s mitochondrial DNA sticks, it could become a source of infertility. Previous studies showed that sperm cells with elevated amounts of mtDNA experience decreased sperm counts and motility. A new study found that other animals “show multiple mechanisms that may contribute to maternal mitochondrial inheritance in different organisms,” said Xinnan Wang, a mitochondrial cell biologist at the Stanford University School of Medicine. This study connects to our lesson in AP Biology on the concept of genetics and how our DNA is passed on from our parents. Specifically, we previously learned how our mitochondrial DNA is almost completely from our mother, as the egg contains way more mitochondrial DNA than the sperm, allowing us to track ancestry by maternal mitochondrial DNA. This study expands our understanding of this concept. According to Temiakov, there are probably other unidentified mechanisms in sperm cells that regulate mtDNA, as a future area for research as it is crucial to better understand mitochondrial diseases and how to treat them. What do you think would happen if the mtDNA is passed on equally from both parents?

By Ynse. Photo from Flickr http://www.flickr.com/photos/ynse/1531699476/

It turns out that kids with obese fathers have unique epigenetic changes that can affect their health… for the worse.

According to a recent study, “children with obese fathers have different epigenetic markings on the gene for insulin-type growth factor 2 (IGF2) than children with fathers of normal weight.”

Children with obese fathers have less methylation on a specific region of the IGF2 gene. Sadly, this occurrence is linked with many types of cancers such as ovarian cancer.

However, it is too soon to tell if these epigenetic changes are directly linked to the children’s’ health.

According to the biologist Gudrun Moore, “it is tempting to over-emphasize the role of a small number of parent-of-origin expressing genes and to speculate about the effects of modest variation in methylation, but we must not be too hasty to blame either parent for their offspring’s health outcomes.”

However, other researchers are sure that that your parent’s environment and habits affect children’s health.

According to Michael Skinner, this research “suggests that environmental epigenetics might be the mechanism for these effects.”

Maybe now both the mother and father have to be careful about what they eat during the pregnancy. Sorry Dads-to-be, you are going to have to eat healthy now!

For more information on epigenetics and health, you can visit these links.

http://www.economist.com/news/science-and-technology/21565573-some-effects-smoking-may-be-passed-grandmother

http://healthletter.mayoclinic.com/editorial/editorial.cfm/i/249/t/Understanding%20epigenetics/

Photo credit: http://www.flickr.com/photos/ynse/1531699476/

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: Father

Where Did Father’s Mitochondrial DNA Go?

Epigenetics, Dads, and Obesity

Archives