Study shows how mitochondrial genes are passed from mother to child

May 3, 2012, Oregon Health & Science University

Research conducted at the Oregon National Primate Research Center at Oregon Health & Science University helps answer some long-standing questions about how certain disease-causing gene mutations are inherited.

The research specifically focused on gene mutations in cell mitochondria that can cause several diseases, including forms of cancer, diabetes, infertility and neurodegenerative diseases. With this new information, we now better understand how and when these mutations are passed to children to improve diagnosis and prevention. The research will be published online in the journal Cell Reports on Thursday May 3.

Shoukhrat Mitalipov, Ph.D., who previously developed a method for preventing the passing of genetic mutations from mother to infant in 2009, directed the research.

This latest breakthrough, which was conducted in rhesus macaque monkeys because of their similarity to humans, demonstrates the specific stage of early embryonic development when genetic mutations are passed from mother to fetus. This stage, referred to by scientists as "the bottleneck," occurs when an early embryo called blastocyst, transitions into a fetus.

To conduct the research, Mitalipov and colleagues needed to design a way to mark and track specific mitochondrial genes as they transitioned from egg, through fertilization, to embryo and then to fetus. This was accomplished by combining two separate mitochondrial genomes into one . More specifically, one-half of an egg cell from a species of Indian-continent rhesus macaque monkey was merged with one-half of an egg cell from a Chinese-continent monkey. Because these animal species have distinct mitochondrial gene sequences (like breeding two distinct species of dogs), their genetics could be tracked closely.

The microscopic manipulation of splitting and uniting two halved egg cells takes specialized skills and expertise, which the Mitalipov lab has developed over a period of several years. A link to a video explaining this process can be found in the multimedia section of this press release.

By studying the development of these joined and then fertilized eggs, scientists were surprised to see that eggs transitioned from containing a 50/50 split of genetics to a fetus that contained a nearly 100 percent either Indian or Chinese-based genome.

"We discovered that during early development, each individual cell in the eight-cell embryo would contain varying percentages of the Indian and Chinese rhesus genes. Some would be a 50/50 split. But others would be 90/10 and so on," explained Mitalipov. "When these percentages were combined as a whole embryo, the average genetic split between the two species was about equal as initially created. However, later during the transition from a blastocyst to fetus, the genetics would swing one way or another. The resulting offspring would have always a genome that is predominantly Chinese or Indian. Our study tells us precisely when this mitochondrial gene switch occurs and how this can lead to disease."

This finding raises significant questions about validity of currently methods for in early embryos, when a woman is known to carry a mitochondrial gene mutation may pass a disease to her children.

"The current pre-implantation genetic diagnosis method is to examine genetic disease risk is by taking one cell from an early eight-cell embryo, and then looking for mutations in that one particular cell. This is done to predict if the remaining embryo is mutation-free," explained Mitalipov.

"The problem with this approach is that you may choose a cell that may not have mutations. But that does not mean the remaining cells in an embryo are mutation-free. Our research suggests that such approach could be flawed because diagnosis takes place prior to the stage when an offspring's mitochondrial genetics is truly established."

With this new information and with additional data gathered through further research, Mitalipov and colleagues believe that new methods for genetic diagnosis for mitochondrial disease should be located. The research also demonstrates that the Mitalipov lab's previously developed method for preventing the passing of mitochondrial mutations from mother to child is highly successful.

Explore further: World's first chimeric monkeys are born

Related Stories

World's first chimeric monkeys are born

January 5, 2012
Researchers have produced the world's first chimeric monkeys. The bodies of these monkeys, which are normal and healthy, are composed of a mixture of cells representing as many as six distinct genomes. The advance holds great ...

Mitochondrial genome mutates when reprogrammed

July 28, 2011
Induced pluripotent stem cells (iPS cells) are truly talented multi-taskers. They can reproduce almost all cell types and thus offer great hope in the fight against diseases like Alzheimer's and Parkinson's. However, it would ...

Recommended for you

Epigenetics study helps focus search for autism risk factors

January 16, 2018
Scientists have long tried to pin down the causes of autism spectrum disorder. Recent studies have expanded the search for genetic links from identifying genes toward epigenetics, the study of factors that control gene expression ...

Group recreates DNA of man who died in 1827 despite having no body to work with

January 16, 2018
An international team of researchers led by a group with deCODE Genetics, a biopharmaceutical company in Iceland, has partly recreated the DNA of a man who died in 1827, despite having no body to take tissue samples from. ...

The surprising role of gene architecture in cell fate decisions

January 16, 2018
Scientists read the code of life—the genome—as a sequence of letters, but now researchers have also started exploring its three-dimensional organisation. In a paper published in Nature Genetics, an interdisciplinary research ...

Study advances gene therapy for glaucoma

January 16, 2018
While testing genes to treat glaucoma by reducing pressure inside the eye, University of Wisconsin-Madison scientists stumbled onto a problem: They had trouble getting efficient gene delivery to the cells that act like drains ...

How incurable mitochondrial diseases strike previously unaffected families

January 15, 2018
Researchers have shown for the first time how children can inherit a severe - potentially fatal - mitochondrial disease from a healthy mother. The study, led by researchers from the MRC Mitochondrial Biology Unit at the University ...

Genes that aid spinal cord healing in lamprey also present in humans

January 15, 2018
Many of the genes involved in natural repair of the injured spinal cord of the lamprey are also active in the repair of the peripheral nervous system in mammals, according to a study by a collaborative group of scientists ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.