Rare cell analysis using sample splitting and DNA tags
View Patent ↗The present invention provides systems, apparatuses, and methods to detect the presence of fetal cells when mixed with a population of maternal cells in a sample and to test fetal abnormalities, e.g. aneuploidy. The present invention involves labeling regions of genomic DNA in each cell in said mixed sample with different labels wherein each label is specific to each cell and quantifying the labeled regions of genomic DNA from each cell in the mixed sample. More particularly the invention involves quantifying labeled DNA polymorphisms from each cell in the mixed sample.
1. A method for determining a fetal abnormality in a maternal blood sample, the method comprising:
obtaining an array of discrete addressable locations of maternal and fetal cells or genomic DNA obtained from a maternal blood sample, wherein each location comprises 0 or 1 fetal cell or fetal genome;
labeling one or more genomic DNA regions in the array using primers that are specific to each genomic DNA region, wherein each genomic region is labeled with a unique tag sequence to identify the presence or absence of a DNA polymorphism in each genomic DNA region and a location of the discrete addressable location of the genomic DNA region in the array;
amplifying the genomic DNA regions; and
determining the presence or absence of a fetal abnormality by analyzing said labeled, amplified genomic DNA regions.
2. The method of claim 1 , wherein analyzing the labeled, amplified genomic DNA regions comprises quantifying the labeled DNA regions.
3. The method of claim 1 , further comprising identifying non-maternal alleles at the discrete addressable locations by comparing a ratio of maternal to paternal alleles at the discrete addressable locations.
4. The method of claim 1 , further comprising amplifying the genomic DNA regions and determining the presence of one or more polymorphisms which are amplified using a polymerase chain reaction (PCR) method.
5. The method of claim 4 , wherein the polymorphism comprises a short tandem repeat (STR) or a single nucleotide polymorphism (SNP).
6. The method of claim 4 , wherein the PCR method comprises multiplex PCR.
7. The method of claim 4 , further comprising an additional amplification step performed using nested primers.
8. The method of claim 1 , wherein the genomic DNA regions are labeled using a PCR primer comprising a primer element, a sequencing element, and the unique tag sequence.
9. The method of claim 8 , wherein the primer element is configured to amplify a genomic DNA region to generate amplicons.
10. The method of claim 8 , wherein the sequencing element is configured to sequence the amplicons.
11. The method of claim 8 , wherein the unique tag sequence comprises a nucleic acid sequence that is 4 to 20 nucleic acid residues in length and is configured to pool the amplicons from all discrete addressable locations following the amplification step, wherein each unique tag sequence is specific for a single addressable location.
12. The method of claim 1 , wherein determining the presence or absence of a fetal abnormality comprises performing ultra-deep sequencing or quantitative genotyping.
13. The method of claim 12 , wherein the quantitative genotyping is performed using one or more molecular inversion probes.
14. The method of claim 1 , wherein the fetal abnormality comprises an aneuploidy selected from the group consisting of: trisomy 13, trisomy 18, trisomy 21 (Down Syndrome), Klinefelter Syndrome (XXY), monosomy, triploidy, tetraploidy, or other irregular number of sex or autosomal chromosomes, and a combination thereof.