New Study Allows Fetal Genome Sequencing From Maternal Blood Samples
Scientists from the Stanford University School of Medicine have managed to sequence the genome of a fetus through the use of a blood sample taken from the mother for the first time. The new discovery has been published on the 4th of July, in the journal Nature. The new discovery is based on research done by scientists at the University of Washington, who were able to sequence the genome of the unborn child by using DNA samples of the parents and the mother’s blood sample.
One of the breakthroughs made by the researchers at Stanford was that DNA from the father was no longer required for the genome sequencing. This is especially useful if the father of the child is unknown or if the father doesn’t want to give a DNA sample. “We’re interested in identifying conditions that can be treated before birth, or immediately after”, said Professor Stephen Quake, Ph.D., who is also the lead author of the study.
Scientists say that because the costs of this new technology will probably continue to drop, thus allowing researchers to discover genetic disorders within the first trimester of pregnancy. Through this new study, researchers have also shown that sequencing the exome, which is only the coding part of the genome, can be relevant to further clinical studies.
In their research, scientists managed to sequence the exome and genome of an unborn child, thus discovering it suffered from a syndrome called DiGeorge. This is caused by a deletion of the chromosome 22 and cause various symptoms, the most common symptoms being neuromuscular and cardiac problems. The severity of the manifestations can vary from patient to patient.
“In this paper, Quake’s group elegantly shows how sequencing of the exome can show that a fetus has inherited DiGeorge syndrome from its mother”, said Dr. Diana Bianchi, the director of the Mother Infant Research and also member of the Verinata Health Inc., the company that had already provided genetic testing by using earlier technology also developed by Professor Stephen Quake.
Prenatal diagnosis is not a new technology. Women have been undergoing different tests, such as amniocentesis and chorionic villus sampling, as an attempt to early diagnose if their children suffer from genetic disorders. These sort of tests involved obtaining cells from the unborn child through the use of a needle inserted in the uterus. This procedure is dangerous and can lead to miscarriage rather often, whilst also being able to detect only a small number of genetic disorders.
The new technology developed by Dr. Quake is based on the fact that the pregnant woman’s blood also contains the DNA of her fetus. Back in 2008, Dr. Quake’s laboratory managed to pioneer the use of fetal DNA levels in maternal blood in order to diagnose conditions such as Down syndrome or other genetic disorders caused by missing or extra chromosomes. This test is currently being marketed by four companies in the United States. However, these tests do not offer a full genetic profile, thus not being able to discover more subtle genetic disorders.
The new study has taken blood sampling a step further. By comparing the relative levels of DNA from regions containing both maternal and paternal DNA, scientists managed to identify and isolate the fetal DNA. Maternal DNA can be found in both the mother and the fetus whilst paternal DNA can only be found in the fetus. The new method has been tested on a number of two pregnancies. One of the mothers was suffering from the DiGeorge syndrome whilst the other didn’t. The sequencing of the genome and exome of the mother suffering from the DiGeorge syndrome showed that her unborn child would also suffer from the same genetic disorder.
“We always knew that detecting fetal chromosomal abnormalities was just the tip of the iceberg, and that diagnosing individual gene defects was the future. This important study confirms our ability to detect individual fetal gene defects simply by testing mom’s blood”, said Dr. Yair Blumenfeld, the co-author of the study, who is also an assistant professor.
Scientists from the Stanford University School of Medicine are already planning on developing this new technique in order to provide it for clinical use.