Fetal Genome Sequenced Without Father's DNA in New Procedure

by Cassandra R. Elias

In the News: Major Development in Genetic and Paternity Testing

Genome Testing

However, the genome sequencing in the new study did not require the father's DNA. This is presented as a clear advantage when the child's true paternity may not be known or the father is unwilling or unavailable to provide DNA. This also brings us closer to fetal genetic testing becoming more routine.

"We're interested in identifying conditions that can be treated before birth, or immediately after," said Stephen Quake, PhD, the Lee Otterson Professor in the School of Engineering and Professor of Bioengineering and Applied Physics.

"Without such diagnoses, newborns with treatable metabolic or immune system disorders suffer until their symptoms become noticeable and the causes determined," he continued. Quake is the senior author of the research.

Former graduate student H. Christina Fan, PhD, who's now a senior scientist at ImmuMetrix, as well as current graduate student Wei Gu are co-first authors of the article.

As the cost of such technology continues to drop, it will become increasingly common to diagnose genetic diseases within the first trimester of pregnancy, the researchers believe. In fact, they showed that sequencing just the exome, the coding portion of the genome, can provide clinically relevant information.

In the new study, the researchers were able to use the whole genome and exome sequences they obtained to determine that a fetus had DiGeorge syndrome, which is caused by a short deletion of chromosome 22.

Although the exact symptoms and their severity can vary among affected individuals, it's associated with cardiac and neuromuscular problems, as well as cognitive impairment. Newborns with the condition can have significant feeding difficulties, heart defects and convulsions due to excessively low levels of calcium.

Prenatal diagnosis is not new. For decades, women have undergone amniocentesis or chorionic villus sampling in an attempt to learn whether their fetus carries genetic abnormalities.

These tests rely on obtaining cells or tissue from the fetus through a needle inserted in the uterus — a procedure that can itself lead to miscarriage in about one in 200 pregnancies. They also detect only a limited number of genetic conditions. It's believed that this new technique will discover genetic anomalies that occur within chromosomes and other DNA.

Naturally, this raises ethical questions about when and why to use the test. Some would say to be prepared in the event of a child who will have special needs, others would say to terminate. It goes without saying that the idea of being able to treat a fetus for a curable condition prior to birth is an exciting notion.

On the flip-side, there's the ethical question of its being used to terminate gender based pregnancies in certain countries.

Regardless, this is an exciting scientific discovery that scientists plan to continue testing. What do you think about this development? An exciting discovery or a slippery slope or both?


Medical reference:
- Non-invasive prenatal measurement of the fetal genome. H. Christina Fan, Wei Gu, Jianbin Wang, Yair J. Blumenfeld, Yasser Y. El-Sayed & Stephen R. Quake. Nature (2012) doi:10.1038/nature11251.Received 01 March 2012. Accepted 23 May 2012. Published online 04 July 2012. Accessed July 5, 2012.