Subscribe to the BioNews newsletter for free

Login
Advanced Search

Search for
BioNews


Print Page Follow BioNews on Twitter BioNews RSS feed

Like the Progress Educational Trust on Facebook



King's College London - Health: More than a medical matter





Whole fetal genome sequenced for the first time

11 June 2012

By Dr Daniel Grimes

Appeared in BioNews 660

Researchers have sequenced the entire genome of an 18 and a half-week-old fetus using DNA samples from the blood of its mother and saliva samples from its father. These findings provide a proof of principle that a fetus can be examined for genetic conditions using non-invasive technologies.

Currently, non-invasive screening is used to detect conditions where there is an extra copy of a chromosome, known as trisomy - including Down's syndrome, where there are three copies of chromosome 21.

This study, published in Science Translational Medicine, shows that it is possible to non-invasively sequence the whole genome of a fetus and to use that to check for smaller changes in the DNA, including more than 3000 single gene disorders.

'If the genome is a book, and a trisomy is an extra chapter, we want to find every typo', lead researcher Dr Jay Shendure of the University of Washington in Seattle told New Scientist.

Single gene, or Mendelian, disorders affect around one percent of live births, and include cystic fibrosis and Huntington's disease. Currently, a small number of specific Mendelian disorders are screened for during pregnancy, but this requires the use of invasive procedures that increase the risk of miscarriage

The team of researchers, primarily based at the University of Washington, exploited the fact that around 13 percent of DNA in a pregnant woman's blood plasma - known as cell-free DNA - originates from the fetus.

Looking for small variations in the letters of the genetic code, they compared the sequence of the cell-free DNA to the mother's DNA, which was sequenced from a blood sample, and so would be 100 percent her own. Any variants found in the cell-free DNA but not in the DNA from the mother's blood were assumed to have come from the fetus.

Further confirmation that these were sections of DNA from the fetus was made by comparing variants to the father's DNA, which was sequenced from a saliva sample. Variants unique to him that appeared in the cell-free DNA must have been inherited by the fetus.

After birth, the baby's genome was sequenced from cord blood, showing their predictions were 98 percent accurate. They also tested their techniques on a second pregnant woman with an 8.2-week-old fetus, with 95 percent accuracy, which suggests these methods could be used to screen very young fetuses.

As well as heritable variants, the researchers looked for spontaneous mutations, identifying 39 of the 44 that were discovered after birth. However, both the New York Times and Science Now reported that they also identified 25 million false positives.

Dr Shendure suggested that the technique could be available in the clinic within five years, estimating the cost at $50,000 per child. However, he warned that the ability to read the genome and find genetic variants far out-strips our ability to understand the consequences on the development and health of a child. 'There will be many mutations whose impact we just don't know', he told Science Now.

Professor Dennis Lo, the pathologist who first discovered that fetal DNA circulates in the mother's blood, has urged caution. Speaking to Science Now, he said: 'I don't think it would be ethical to use this to screen for late-onset diseases like Alzheimer's or cardiovascular diseases, for example'.

 

SOURCES & REFERENCES
New York Times | 06 June 2012
 
Nature News | 06 June 2012
 
AAAS Press Release | 06 June 2012
 
Science Translational Medicine | 06 June 2012
 
Science NOW | 06 June 2012
 
New Scientist | 07 June 2012
 

RELATED ARTICLES FROM THE BIONEWS ARCHIVE

10 September 2012 - by Emma Stoye 
Scientists have found that 80 percent of DNA in the human genome, previously thought to be of no use, have important functions... [Read More]
09 July 2012 - by Dr Lux Fatimathas 
US researchers have for the first time sequenced the genome of a fetus using only a blood sample from the mother. It is hoped this new form of non-invasive sampling could allow doctors to screen for a range of genetic diseases prenatally, with minimal risk to the fetus... [Read More]
18 June 2012 - by Dr Louisa Petchey 
The most extensive catalogue of the trillions of microbes that live in and on humans - called the human microbiome - has been published by an international team of scientists... [Read More]

12 September 2011 - by Vardit Ravitsky 
An up-and-coming technology will soon allow genetic testing of a fetus with a simple maternal blood test early in the first trimester of the pregnancy by isolating cell-free fetal DNA in the mother's plasma. Currently, obtaining reliable diagnostic genetic information requires invasive testing with Chorionic Villus Sampling (CVS) or amniocentesis. Both carry a risk of miscarriage and are performed between weeks 10 and 20 of the pregnancy... [Read More]
15 September 2008 - by Jane Fisher 
Antenatal Results and Choices (ARC) is the only UK charity providing non-directive information and support to parents before, during and after antenatal testing and when an abnormality is diagnosed in an unborn baby. We have 20 years' experience of talking to parents on our National Helpline on all aspects of... [Read More]
16 June 2008 - by Dr Zuzana Deans and Dr Ainsley Newson 
Dr Phillipa Brice's accompanying commentary highlights how non-invasive testing of free fetal DNA (ffDNA) in pregnancy could transform women's experiences of antenatal screening and prenatal diagnosis. NIPD is already available for foetal sex, rhesus D blood type and some Mendelian conditions such as achondroplasia, with tests for aneuploidy detection and... [Read More]
16 June 2008 - by Dr Philippa Brice 
Antenatal care in the UK includes various forms of screening intended to assess the health of the mother and fetus; at present this includes the use of ultrasound imaging to check on physical development of the fetus, and serum screening using maternal blood to determine blood group, identify the presence... [Read More]
25 September 2006 - by Dr Jess Buxton 
Non-invasive prenatal tests to identify fetuses at risk of genetic disorders as early as the sixth week of pregnancy are now a reality, say British scientists. A team based at the Institute of Child Health in London and Bristol has successfully carried out simple blood tests... [Read More]

HAVE YOUR SAY
Be the first to have your say.

You need to Login or Register to add comments.

By posting a comment you agree to abide by the BioNews terms and conditions

 


 

- click here to enquire about using this story.

Printer Friendly Page

Published by the Progress Educational Trust
RISK ASSESSMENT:
BREAST CANCER, PREDICTION AND SCREENING
FREE public event in central London, 6.30pm on Thursday 8 May 2014 - find out more HERE

ANNIVERSARY APPEAL
Please donate HERE, so that the Progress Educational Trust can continue throughout 2014 (and beyond) while keeping BioNews FREE for you to read

The Progress Educational Trust was shortlisted for the Charity Times Awards 2011

Advertise your products and services HERE - click for further details

Good Fundraising Code

Become a Friend of PET HERE, and give the Progress Educational Trust a regular donation