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.

1 . A fraction of a sample of the blood plasma or serum of a pregnant woman in which, as the result of said sample having been submitted to a size separation, the extracellular DNA present therein substantially consists of DNA comprising 500 base pairs or less.  
     
     
         2 . A sample-fraction according to  claim 1  which is substantially cell-free.  
     
     
         3 . A sample-fraction according to  claim 1 , wherein the size separation was carried out by chromatography or electrophoresis, by density gradient centrifugation or by methods utilising nanotechnological means.  
     
     
         4 . A sample-fraction according to  claim 3 , wherein the chromatography and, respectively, electrophoresis was chromatography on agarose or polyacrylamide gels, ion-pair reversed-phase high performance liquid chromatography (IP RP HPLC), capillary electrophoresis in a self-coating, low-viscosity polymer matrix, selective extraction in microfabricated electrophoresis devices, microchip electrophoresis on reduced viscosity polymer matrices or adsorptive membrane chromatography.  
     
     
         5 . A sample-fraction according to  claim 3 , wherein the method utilizing nanotechnological means was making use of microfabricated entropic trap arrays.  
     
     
         6 . The use of a sample-fraction according to  claim 1  for the non-invasive detection of fetal genetic traits.  
     
     
         7 . The use according to  claim 6 , wherein the fetal genetic trait to be detected is the fetal RhD gene in a pregnancy at risk for HDN (hemolytic disease of the fetus and the newborn) or a fetal Y chromosome-specific sequence in a pregnancy at risk for an X chromosome-linked disorder.  
     
     
         8 . The use according to  claim 6 , wherein the fetal genetic trait to be detected is a chromosomal aberration, a hereditary Mendelian genetic disorder and, respectively, a genetic marker associated therewith, or a fetal genetic trait which may be decisive when paternity is to be determined.  
     
     
         9 . The use according to  claim 7 , wherein the X chromosome-linked disorder is hemophilia or fragile X syndrome.  
     
     
         10 . The use according to  claim 8 , wherein the chromosomal aberration is an aneuploidy.  
     
     
         11 . The use according to  claim 8 , wherein the chromosomal aberration is associated with Down's syndrome.  
     
     
         12 . The use according to  claim 8 , wherein the hereditary Mendelian genetic disorder is a single gene disorder.  
     
     
         13 . The use according to  claim 12 , wherein the single gene disorder is cystic fibrosis or a hemoglobinopathy.  
     
     
         14 . The use according to  claim 6 , wherein the detection of the fetal genetic traits is carried out by PCR (polymerase chain reaction) technology, ligand chain reaction or probe hybridisation techniques or by means of nucleic acid arrays.  
     
     
         15 . A process for performing non-invasive detection of fetal genetic traits which comprises subjecting a sample of the blood plasma or serum of a pregnant woman to a size separation so as to obtain a fraction of said sample in which the extracellular DNA present therein substantially consists of DNA comprising 500 base pairs or less, and determining the fetal genetic trait(s) to be detected by submitting such fraction to PCR (polymerase chain reaction) technology, ligase chain reaction or probe hybridisation techniques, or to nucleic acid arrays.  
     
     
         16 . A process according to  claim 15 , wherein the fetal genetic trait to be detected is the fetal RhD gene in a pregnancy at risk for HDN (hemolytic disease of the fetus and the newborn) or a fetal Y chromosome-specific sequence in a pregnancy at risk for an X chromosome-linked disorder.  
     
     
         17 . A process according to  claim 15 , wherein the fetal genetic trait to be detected is a chromosomal aberration, a hereditary Mendelian genetic disorder and, respectively, a genetic marker associated therewith, or a fetal genetic trait which may be decisive when paternity is to be determined.  
     
     
         18 . A process according to  claim 16 , wherein the X chromosome-linked disorder is hemophilia or fragile X syndrome.  
     
     
         19 . A process according to  claim 17 , wherein the chromosomal aberration is an aneuploidy.  
     
     
         20 . A process according to  claim 17 , wherein the chromosomal aberration is associated with Down's syndrome.  
     
     
         21 . A process according to  claim 17 , wherein the hereditary Mendelian genetic disorder is a single gene disorder.  
     
     
         22 . A process according to  claim 21 , wherein the single gene disorder is cystic fibrosis or a hemoglobinopathy.