119 results about "Fetal dna" patented technology

The present methods are exemplified by a process in which maternal blood containing fetal DNA is diluted to a nominal value of approximately 0.5 genome equivalent of DNA per reaction sample. Digital PCR is then be used to detect aneuploidy, such as the trisomy that causes Down Syndrome. Since aneuploidies do not present a mutational change in sequence, and are merely a change in the number of chromosomes, it has not been possible to detect them in a fetus without resorting to invasive techniques such as amniocentesis or chorionic villi sampling. Digital amplification allows the detection of aneuploidy using massively parallel amplification and detection methods, examining, e.g., 10,000 genome equivalents.

In a first aspect, the present invention features methods for differentiating DNA species originating from different individuals in a biological sample. These methods may be used to differentiate or detect fetal DNA in a maternal sample or to differentiate DNA of an organ donor from DNA of an organ recipient. In preferred embodiments, the DNA species are differentiated by observing epigenetic differences in the DNA species such as differences in DNA methylation. In a second aspect, the present invention features methods of detecting genetic abnormalities in a fetus by detecting fetal DNA in a biological sample obtained from a mother. In a third aspect, the present invention features methods for differentiating DNA species originating from an organ donor from those of an organ recipient. In a fourth aspect, the present invention features kits for differentiating DNA species originating from different individuals in a biological sample.

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.

The invention provides a method useful for detection of genetic disorders. The method comprises determining the sequence of alleles of a locus of interest, and quantitating a ratio for the alleles at the locus of interest, wherein the ratio indicates the presence or absence of a chromosomal abnormality. The present invention also provides a non-invasive method for the detection of chromosomal abnormalities in a fetus. The invention is especially useful as a non-invasive method for determining the sequence of fetal DNA. The invention further provides methods of isolation of free DNA from a sample.

A fractional concentration of clinically-relevant DNA in a mixture of DNA from a biological sample is determined based on amounts of DNA fragments at multiple sizes. For example, the fractional concentration of fetal DNA in maternal plasma or tumor DNA in a patient's plasma can be determined. The size of DNA fragments in a sample is shown to be correlated with a proportion of fetal DNA and a proportion of tumor DNA, respectively. Calibration data points (e.g., as a calibration function) indicate a correspondence between values of a size parameter and the fractional concentration of the clinically-relevant DNA. For a given sample, a first value of a size parameter can be determined from the sizes of DNA fragments in a sample. A comparison of the first value to the calibration data points can provide the estimate of the fractional concentration of the clinically-relevant DNA.

A system and method for determining the genetic data for one or a small set of cells, or from fragmentary DNA, where a limited quantity of genetic data is available. Genetic data for the target individual is acquired and amplified using known methods, and poorly measured base pairs, missing alleles and missing regions are reconstructed using expected similarities between the target genome and the genome of genetically related subjects. In accordance with one embodiment of the invention, incomplete genetic data from an embryonic cell is reconstructed using the more complete genetic data from a larger sample of diploid cells from one or both parents, with or without genetic data from haploid cells from one or both parents, and/or genetic data taken from other related individuals. In accordance with another embodiment of the invention, incomplete genetic data from a fetus is acquired from fetal cells, or cell-free fetal DNA isolated from the mother's blood, and the incomplete genetic data is reconstructed using the more complete genetic data from a larger sample diploid cells from one or both parents, with or without genetic data from haploid cells from one or both parents, and/or genetic data taken from other related individuals. In one embodiment, the genetic data can be reconstructed for the purposes of making phenotypic predictions. In another embodiment, the genetic data can be used to detect for aneuploides and uniparental disomy.

Chromosomal abnormalities are responsible for a significant number of birth defects, including mental retardation. The present invention is related to methods for non-invasive and rapid, prenatal diagnosis of chromosomal abnormalities based on analysis of a maternal blood sample. The invention exploits the differences in DNA between the mother and fetus, for instance differences in their methylation states, as a means to enrich for fetal DNA in maternal plasma sample. The methods described herein can be used to detect chromosomal DNA deletions and duplications. In a preferred embodiment, the methods are used to diagnose chromosomal aneuploidy and related disorders, such as Down's and Turner's Syndrome.

A non-invasive screening or diagnostic method for determining the likelihood of a fetus with a genetic abnormality or a potential pregnancy complication, which utilizes a liquid blood sample from a pregnant woman. Antibodies specific to a section of histone 3.1 which is exposed to a far greater extent in chromatin of fetal origin than in chromatin of maternal origin are used to sequester and isolate such fetal nucleosomes including the associated fetal DNA. Following isolation/enrichment of such fetal DNA, genetic analysis is carried out using known molecular diagnostics.

The present invention relates to the identification of fetal specific nucleic acids and fetal cell markers in maternal plasma or serum. In particular, the present invention relates to methods which rely on the analysis of polymorphic alleles of a population to determine an allele which is possessed by the fetus but absent from the mother. Fetal specific alleles identified using the methods of the invention can be used to quantify fetal DNA from maternal plasma or serum. In addition, antigens encoded by alleles identified using the methods of the invention can be targeted in methods of isolating or detecting fetal cells.

A method of detecting the presence or absence of the fetal DNA sequence of interest in fetal DNA derived from a sample of peripheral blood obtained from a pregnant woman is described. The method involves obtaining a sample peripheral blood from a pregnant woman, treating the sample of peripheral blood such that the fetal DNA present in the fetal nucleated cells is made available for detection and detecting the presence or absence of the fetal DNA sequence of interest in the available fetal DNA. The proportion of fetal nucleated cells present in the sample of peripheral blood can be increased forming a sample enriched in fetal nucleated cells prior to the detection step. The fetal DNA sequence of interest can be detected by treating the peripheral blood sample such that fetal DNA present in the sample is made available for hybridization with a DNA probe and subsequently contacting the available fetal DNA with a DNA probe hybridizable to fetal DNA of interest under hybridization conditions. The presence or absence of hybridization between the DNA probe and the fetal DNA of interest is detected as an indication of the presence or absence of the fetal DNA of interest.

A system and method for determining the genetic data for one or a small set of cells, or from fragmentary DNA, where a limited quantity of genetic data is available, are disclosed. Genetic data for the target individual is acquired and amplified using known methods, and poorly measured base pairs, missing alleles and missing regions are reconstructed using expected similarities between the target genome and the genome of genetically related subjects. In accordance with one embodiment of the invention, incomplete genetic data is acquired from embryonic cells, fetal cells, or cell-free fetal DNA isolated from the mother's blood, and the incomplete genetic data is reconstructed using the more complete genetic data from a larger sample diploid cells from one or both parents, with or without genetic data from haploid cells from one or both parents, and/or genetic data taken from other related individuals.

Disclosed herein are methods and kits for selectively amplifying, detecting or quantifying a DNA fragment with a specific end sequence, especially generated following restriction enzyme digestion. This method can be used, for example, to detect a hypomethylated DNA fragment. This methods and kits are especially useful in detecting or quantifying a hypomethylated fetal DNA fragment in a maternal plasma sample containing a corresponding hypermethylated maternal DNA fragment.

The invention provides a method useful for detection of genetic disorders. The method comprises determining the sequence of alleles of a locus of interest, and quantitating a ratio for the alleles at the locus of interest, wherein the ratio indicates the presence or absence of a chromosomal abnormality. The present invention also provides a non-invasive method for the detection of chromosomal abnormalities in a fetus. The invention is especially useful as a non-invasive method for determining the sequence of fetal DNA. The invention further provides methods of isolation of free DNA from a sample.

This application describes the discovery that, in a pregnant woman, certain genes (such as RASSF1A, APC, CASP8, RARB, SCGB3A1, DAB2IP, PTPN6, THY1, TMEFF2, and PYCARD) originated from a fetus are highly methylated, whereas the same genes of maternal origin are unmethylated. This discovery allows the easy detection of one or more of these methylated fetal genes in a biological sample from a pregnant woman, serving as a universal indicator of the presence of fetal DNA in the sample. These fetal methylation markers are particularly useful as positive controls for a non-invasive analytical process during which the quality and quantity of fetal DNA are monitored. These newly identified fetal markers can also be measured directly for diagnosis of certain pregnancy-related conditions.

The present invention provides amplification-based methods for detection of genotype, mutations, and/or aneuploidy. These methods have broad applicability, but are particularly well-suited to detecting and quantifying target nucleic acids in free fetal DNA present in a maternal bodily fluid sample.