Non-invasive detection of fetal genetic traits

Abstract

Blood plasma of pregnant women contains fetal and (generally>90%) maternal circulatory extracellular DNA. Most of said fetal DNA contains ≦500 base pairs, said maternal DNA having a greater size. Separation of circulatory extracellular DNA of <500 base pairs results in separation of fetal from maternal DNA. A fraction of a blood plasma or serum sample of a pregnant woman containing, due to size separation (e.g. by chromatography, density gradient centrifugation or nanotechnological methods), extracellular DNA substantially comprising ≦500 base pairs is useful for non-invasive detection of fetal genetic traits (including the fetal RhD gene in pregnancies at risk for HDN; fetal Y chromosome-specific sequences in pregnancies at risk for X chromosome-linked disorders; chromosomal aberrations; hereditary Mendelian genetic disorders and corresponding genetic markers; and traits decisive for paternity determination) by e.g. PCR, ligand chain reaction or probe hybridization techniques, or nucleic acid arrays.

Description

BACKGROUND OF THE INVENTION [0001] The presence of circulatory extracellular DNA in the peripheral blood is a well established phenomenon. In this context, it has been shown that in the case of a pregnant woman extracellular fetal DNA is present in the maternal circulation and can be detected in maternal plasma or serum. Studies have shown that this circulatory fetal genetic material can be used for the very reliable determination, e.g. by PCR (polymerase chain reaction) technology, of fetal genetic loci which are completely absent from the maternal genome. Examples of such fetal genetic loci are the fetal RhD gene in pregnancies at risk for HDN (hemolytic disease of the fetus and newborn) or fetal Y chromosome-specific sequences in pregnancies at risk for an X chromosome-linked disorder e.g. hemophilia or fragile X syndrome. [0002] The determination of other, more complex fetal genetic loci (e.g. chromosomal aberrations such as aneuploidies or chromosomal aberrations associated wit...

AI Technical Summary

Benefits of technology

[0005] This selective enrichment, which is based on size discrimination of circulatory DNA fragments of approximately 500 base pairs or less, leads to a fraction which is largely constituted by fetal extracellular DNA. This permits the analysis of fetal genetic traits including those involved in chromosomal aberrations (e.g. aneuploidies or chromosomal aberrations associated with Down's syndrome) or hereditary Mendelian genetic disorders and, respectively, genetic markers associated therewith (e.g. single gene disorders such as cystic fibrosis or the hemoglobinopathies), the determination of which had, as mentioned above, so far proved difficult, if not impossible. Size separation of extracellular fetal DNA in the maternal circulation thus facilitates the non-invasive detection of fetal genetic traits, including paternally inherited polymorphisms which permit paternity testing.

Problems solved by technology

The determination of other, more complex fetal genetic loci (e.g. chromosomal aberrations such as aneuploidies or chromosomal aberrations associated with Down's syndrome, or hereditary Mendelian genetic disorders and, respectively, genetic markers associated therewith, such as single gene disorders, e.g. cystic fibrosis or the hemoglobinopathies) is, however, more problematic.

This vast bulk of maternal circulatory extracellular DNA renders it difficult, if not impossible, to determine fetal genetic alternations such as those involved in chromosomal aberrations (e.g. aneuploidies) or hereditary Mendelian genetic disorders (e.g. cystic fibrosis or the hemoglobinopathies) from the small amount of circulatory extracellular fetal DNA.