NEW YORK (Reuters Health) - Investigators have devised a technique for selectively enriching fetal DNA in maternal blood samples, permitting the identification of paternally inherited point mutations, such as beta-thalassemia.
Dr. Sinuhe Hahn, at University Hospital in Basel, Switzerland, and colleagues report these findings in the February 16th Journal of the American Medical Association.
A second paper in the same issue reports that fetal mRNA can be extracted from amniotic fluid and characterized by oligonucleotide microarrays. This technology may be used in the development of biomarkers to assess fetal health, the researchers suggest.
Dr. Hahn’s group worked out a technique in which maternal blood samples are subjected to size-fractionation, taking advantage of the fact that circulatory fetal DNA sequences comprise fewer than 300 base pairs, while maternal DNA exceeds 500 base pairs.
Samples were then subjected to polymerase chain reaction (PCR) amplification using peptide-nucleic acids that bind with high affinity to maternal alleles to further select for paternally inherited DNA sequences. Presence of the paternal mutant alleles for beta-thalassemia was then detected by allele-specific real-time PCR.
They tested their technique using 32 maternal blood samples from women whose fetuses were at risk for beta-thalassemia because the father was a carrier for one of four beta-globin gene mutations. The results were verified by comparing the findings from chorionic villus sampling at 10 to 12 weeks of gestation. Three cases were excluded because of low concentration of input DNA.
Other than one false-positive, results from blood matched results of chorionic villus sampling, for a sensitivity of 100% and a specificity of 93.8%.
Dr. Hahn’s group proposes that their method can be used for noninvasive detection of other fetal mutations, such as achondroplasia. Because their technique does not require complex machinery and relies on technology currently in use, they estimate that the cost of a single analysis to be as low as $8.
In the second paper, Dr. Diana W. Bianchi at Tufts-New England Medical Center in Boston, and colleagues analyzed samples of five cell-free amniotic fluid samples from four women who underwent amnioreduction for polyhydramnios, comparing results with two pooled amniotic fluid samples (one from male fetuses and one from females) from women undergoing genetic amniocentesis.
Samples were subjected to oligonucleotide hybridization and microarray data analysis. Five samples hybridized well to the arrays, the authors note.
Gene expression patterns appeared to correlate with sex of the fetus, gestational age, and disease status. Transcripts included those for surfactant proteins, mucins, and keratins. A water transporter gene was found in samples from fetuses with twin-twin transfusion syndrome but not in two patients with hydrops or in the control samples.
The investigators observed no placenta-specific genes.
“The intriguing gene expression differences observed suggest that this technology could facilitate the advancement of human developmental research, as well as the cultivation of new biomarkers for assessment of the living fetus,” Dr. Bianchi’s group concludes.
Source: JAMA 2005;293:836-849. [ Google search on this article ]
MeSH Headings:Cytodiagnosis: Diagnosis: Laboratory Techniques and Procedures: Diagnostic Techniques, Obstetrical and Gynecological: Genetic Techniques: Investigative Techniques: Prenatal Diagnosis: Hydrops Fetalis: Chorionic Villi Sampling: Polymerase Chain Reaction: Point Mutation: Sequence Analysis: Diagnostic Techniques and Procedures: Oligonucleotide Array Sequence Analysis: Gene Expression Profiling: Analytical, Diagnostic and Therapeutic Techniques and EquipmentCopyright © 2002 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.
