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Technology Seminar (18 Feb 2009)



Technology Seminar

Noninvasive Diagnosis of Fetal Aneuploidy by
Shotgun Sequencing DNA from Maternal Blood:
Application of the Fluidigmâ„¢ Digital PCR Platform




Ms. Christina Fan
Ph.D. Candidate, Bioengineering, Stanford Graduate Fellow
Tau Beta Pi Scholarship
Columbia University’s George Vincent Wendell Memorial Medal & Richard Skalak Award

on Wednesday, 18 February 2009
at 3:00 p.m.
Room L6-32, 6/F, Laboratory Block
Genome Research Centre
Li Ka Shing Faculty of Medicine Building,
21 Sassoon Road, Pokfulam, Hong Kong


The current gold standard for diagnosing fetal aneuploidy is by karyotyping fetal cells obtained via invasive procedures such as chorionic villus sampling and amniocentesis. These procedures impose small but significant risk to both the fetus and the mother. The discoveries of intact fetal cells and cell-free fetal nucleic acids in the maternal bloodstream in the past few decades have led to the development of noninvasive fetal diagnosis. While intact fetal cells in maternal blood are rare and difficult to isolate, the amount of cell-free fetal nucleic acids have been found to be present at a significant amount. Because fetal nucleic acids constitute only a small percentage of the total nucleic acids in maternal blood, methods for diagnosing fetal aneuploidy non-invasively developed in the past focused on the allelic variation between the fetus and the mother, and thus depended on the underlying genetic population. Here we present a universally applicable method for the noninvasive detection of fetal aneuploidy. By sequencing cell-free DNA in maternal plasma using next- generation sequencing technology, we obtained a few million short sequence tags per sample.
By counting the number of sequence tags mapped to each chromosome, the over- and under-representation of any chromosome contributed by an aneuploid fetus could be detected. This technique does not require the differentiation of maternal versus fetal DNA, and with large enough sequence tags, it can be applied to arbitrarily small fractions of fetal DNA. We demonstrate the success of this diagnostic technique on a group of 18 pregnant women, including cases of trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), and trisomy 13 (Patau syndrome).

Co-organized with Bio-Gene Technology Ltd

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