Non-invasive methods for detecting non-host DNA in a host using epigenetic differences between the host and non-host DNA
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.
1. A method for differentiating DNA species originating from cells of different individuals, the method comprising the steps of:
(a) obtaining from one of the individuals a biological sample comprising the DNA species originating from the cells of different individuals; and
(b) detecting a methylation difference between the DNA species,
wherein detection of the methylation difference indicates DNA species from different individuals.
2. A method according to claim 1 wherein the biological sample is a fluid or cellular sample or a mixture thereof.
3. A method according to claim 1 wherein the biological sample is plasma or serum.
4. A method according to claim 1 wherein the biological sample is blood.
5. A method according to claim 1 wherein one of the individuals is a pregnant female and the other individual is an unborn fetus.
6. A method according to claim 5 wherein the biological sample is maternal plasma or serum.
7. A method according to claim 6 further comprising the step of:
(c) measuring the concentration of fetal DNA in maternal plasma or serum.
8. A method according to claim 7 wherein the concentration of fetal DNA measured is used to predict, monitor or diagnose or prognosticate a disorder.
9. A method according to claim 6 wherein the methylation difference detected in fetal cells is used as a fetus-specific marker.
10. A method according to claim 5 wherein the methylation difference is associated with a fetal or maternal disorder.
11. A method according to claim 10 wherein the disorder is a chromosomal aneuploidy.
12. A method according to claim 11 wherein the chromosomal aneuploidy is trisomy 21 (Down syndrome).
13. A method according to claim 10 wherein the disorder is preeclampsia.
14. A method according to claim 10 wherein the disorder is an imprinting disorder.
15. A method according to claim 10 wherein the disorder is Prader-Willi syndrome.
16. A method according to claim 10 wherein the disorder is Angelman syndrome.
17. A method according to claim 5 wherein the methylation difference is detected in fetal cell in the placenta.
18. A method according to claim 1 wherein one of the individuals is a transplantation recipient and the other individual is an organ donor.
19. A method according to claim 18 wherein the transplantation is a bone marrow transplantation.
20. A method according to claim 18 further comprising the step of:
(c) measuring the concentration of organ donor and transplantation recipient DNA.
21. A method according to claim 20 wherein the concentration of organ donor and transplantation recipient DNA is used to predict the clinical progress of the transplantation recipient.
22. A method according to claim 1 further comprising the step of:
(c) measuring the concentration of the DNA species.
23. A method according to claim 1 further comprising the step of:
(c) adding sodium bisulfite to the biological sample or to the DNA species.
24. A method according to claim 1 further comprising the step of:
(c) performing a methylation-specific polymerase chain reaction.
25. A method according to claim 1 further comprising the steps of:
(c) amplifying the DNA species to generate a PCR product; and
(d) sequencing the PCR product.
26. A method according to claim 1 further comprising the step of:
(c) performing primer extension.
27. A method according to claim 1 wherein one of the individuals is male and the other individual is female.
28. A method according to claim 27 wherein the methylation difference is detected on an inactivated X chromosome of the female.
29. A method according to claim 28 wherein a methylated DNA sequence on the inactivated X chromosome is used to detect DNA originating from the female.
30. A method according to claim 1 wherein the methylation difference is analyzed inside cells.
31. A method according to claim 30 wherein the methylation difference is analyzed using in-situ methylation-specific polymerase chain reaction.
32. A method according to claim 1 wherein the methylation difference is used to sort or isolate cells from the individuals.
33. A method according to claim 1 wherein the methylation difference is used to purify DNA from the individuals.