Mum's blood test reveals genome of foetus | COSMOS magazine

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WASHINGTON: The entire genome of a foetus can be pieced together from bits of DNA that float through the pregnant mother's blood, which could lead to non-invasive foetal testing.

Until now, the most accurate methods of screening a foetus for potential abnormalities have involved risks to the unborn child because they require doctors to take a sample of foetal tissue by piercing the womb.

Those techniques, such as amniocentesis and chorionic villus sampling, presented a dilemma to expectant moms, particularly among older women who want to screen for chromosomal abnormalities that can increase in likelihood along with maternal age, such as Down syndrome.

Foetal DNA floats in mother's plasma

But according to researchers in Hong Kong, whose work was published in the U.S. journal Science Translational Medicine, the entire foetal genome can be glimpsed floating in the mother's blood.

Foetal DNA makes up about 10% of a pregnant woman's blood plasma. But because DNA molecules in the plasma exist in fragments, piecing together which ones belonged to the foetus proved technically difficult.

Lead author Dennis Lo and his team discovered in 1997 'floating' DNA from the foetus in the mother's blood, and laboratories have widely used this technique to test for gender as well as foetal genetic and chromosomal disorders.

Genome constructed using mum, dad's genes

However the span of such tests has been limited to one disease or genetic characteristic at a time.

The latest research isolated foetal genetic signatures in the floating DNA, then compared its characteristics against the genetic maps of the mother and father.

That way, scientists were able to construct a genome-wide genetic map of the foetus, which they could then scan for variations and mutations.

Future use in cancer diagnostics and transplants

"Before the present work, it was not clear whether the entire foetal genome is represented in maternal plasma," wrote Lo.

"This information is important because it demonstrates that a non-invasive genome-wide scan of the foetal genome from maternal plasma is possible."

Lo said the method of identifying nucleic acids in the plasma could also help in the fields of cancer diagnosis and tissue transplants.

"It would be interesting to investigate whether key features of the high-resolution size profile for circulating foetal DNA can also be seen in circulating tumour DNA and donor graft-derived DNA," the study said.

via cosmosmagazine.com