Methods and compositions for noninvasive prenatal diagnosis of fetal aneuploidies
The invention provides methods and compositions for noninvasive prenatal diagnosis of fetal aneuploidies. A large panel of differentially methylated regions (DMRs) have been identified. Certain of these DMRs are hypomethylated in adult female blood DNA and hypermethylated in fetal DNA, whereas others are hypermethylated in adult female blood DNA and hypomethylated in fetal DNA. Moreover, DMRs that are hypomethylated in adult female blood DNA and hypermethylated in fetal DNA have been shown to accurately predict a fetal aneuploidy in fetal DNA present in a maternal blood sample during pregnancy. In the methods of the invention, hypermethylated DNA is physically separated from hypomethylated DNA, preferably by methylated DNA immunoprecipitation.
1. A method for prenatal diagnosis of trisomy 21 using a sample of maternal blood, the method comprising:
a) obtaining a hypermethylated DNA sample by physically separating hypermethylated DNA from hypomethylated DNA in a sample of maternal blood, without chemically altering or enzymatically digesting the hypomethylated DNA or hypermethylated DNA;
b) amplifying a plurality of differentially methylated regions (hereinafter DMRs), wherein said plurality of DMRs consists of eight regions amplified with oligonucleotide primers as follows:
(i) a DMR comprising a sequence as shown in SEQ ID NO: 36 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 7 and 8;
(ii) a DMR comprising a sequence as shown in SEQ ID NO: 37 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 9 and 10;
(iii) a DMR comprising a sequence as shown in SEQ ID NO: 38 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 11 and 12;
(iv) a DMR comprising a sequence as shown in SEQ ID NO: 39 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 13 and 14;
(v) a DMR comprising a sequence as shown in SEQ ID NO: 40 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 15 and 16;
(vi) a DMR comprising a sequence as shown in SEQ ID NO: 42 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 19 and 20;
(vii) a DMR comprising a sequence as shown in SEQ ID NO: 43 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 21 and 22; and
(viii) a DMR comprising a sequence as shown in SEQ ID NO: 44 amplified using oligonucleotide primers comprising sequences as shown in SEQ ID NOs: 23 and 24;
c) obtaining a hypermethylation value for the hypermethylated DNA sample based on the amplification of the plurality of DMRs;
d) comparing the hypermethylation value of the hypermethylated DNA sample to (i) a standardized normal reference hypermethylation value for a normal fetus or (ii) a range of standardized trisomy 21 reference hypermethylation values for a trisomy fetus;
e) determining that (i) the hypermethylation value for the hypermethylated DNA sample is higher than the standardized normal reference hypermethylation value or (ii) the hypermethylation value for the hypermethylated DNA sample is within the range of the standardized trisomy 21 reference hypermethylation values; and
f) diagnosing trisomy 21.
2. The method of claim 1 , wherein the maternal blood sample is a maternal peripheral blood sample or a fractionated portion of maternal peripheral blood.
3. The method of claim 1 , wherein hypermethylated DNA is separated from hypomethylated DNA using an antibody that immunoprecipitates methylated DNA.
4. The method of claim 1 , wherein hypermethylated DNA is physically separated from hypomethylated DNA by Methylation DNA Immunoprecipitation.
5. The method of claim 1 , wherein the hypermethylated DNA is amplified by ligation-mediated polymerase chain reaction (hereinafter LM-PCR).
6. The method of claim 5 , wherein the levels of the plurality of DMRs are also determined in a total untreated maternal blood DNA sample as a control of the LM-PCR efficiency.
7. The method of claim 1 , wherein the levels of the plurality of DMRs in the hypermethylated DNA sample are determined by real time quantitative polymerase chain reaction.