Rapid aneuploidy detection
Massively parallel sequencing of cell-free, maternal plasma DNA was recently demonstrated to be a safe and effective screening method for fetal chromosomal aneuploidies. Here, we report an improved sequencing method achieving significantly increased throughput and decreased cost by replacing laborious sequencing library preparation steps with PCR employing a single primer pair. Using this approach, samples containing as little as 4% trisomy 21 DNA could be readily distinguished from euploid samples.
1. A method of detecting the presence or absence of aneuploidy, comprising:
a) contacting a sample comprising plasma DNA from a human patient with a single primer pair, wherein said primer pair comprises a first primer and a second primer,
wherein both said first primer and said second primer are designed to anneal to long interspersed nucleotide elements (LINEs) present on a reference set of all twenty-two autosome human non-aneuploid chromosomes that would generate, during amplification, an expected distribution for said twenty-two autosome human non-aneuploid chromosomes,
wherein said plasma DNA comprises at least a portion of all twenty-two autosome patient chromosomes;
b) amplifying, using polymerase chain reaction, at least a portion of said plasma DNA using the single primer pair, whereby a plurality of amplicons from said LINEs are produced,
wherein said plurality of amplicons are distinct from one another,
wherein each of said plurality of amplicons is less than 180 bp in length; and
wherein said plurality of amplicons comprise at least two amplicons from each of said twenty-two autosome patient chromosomes;
c) sequencing at least 5 nucleotides of each of the amplicons in the plurality of amplicons;
d) aligning in silico the sequenced amplicons from each of said twenty-two autosome patient chromosomes to said reference set of all twenty-two autosome human non-aneuploid chromosomes in order to produce a query distribution for each of said twenty-two autosome patient chromosomes,
wherein said query distribution comprises a normalized count of the number of sequenced amplicons at each position where they align to said reference set of all twenty-two autosome human non-aneuploid chromosomes; and
e) identifying:
i) the presence of aneuploidy based upon finding at least one normalized count difference between said query distribution for at least one of said twenty-two autosome patient chromosomes and said expected distribution for a corresponding at least one of said twenty-two autosome human non-aneuploid chromosomes, or
ii) the absence of aneuploidy based upon not finding at least one normalized count different difference between said query distribution and said expected distribution.
2. The method of claim 1 , wherein said sequencing at least 5 nucleotides of each of the amplicons comprises sequencing at least 15 nucleotides of each of the amplicons in the plurality of amplicons.
3. The method of claim 1 , wherein the presence of aneuploidy is identified in the sample.
4. The method of claim 1 , wherein the absence of aneuploidy is identified in the sample.
5. The method of claim 1 , wherein the average length of the plurality of amplicons is less than 150 bp.
6. The method of claim 1 , wherein the sample is maternal plasma and the plasma DNA comprises fetal chromosomes.
7. The method of claim 1 , wherein unique sequence tags are incorporated at a 5′ end of the primers.
8. The method of claim 1 , wherein, in step e): i) said at least one of said twenty-two autosome patient chromosomes comprises all twenty-two autosome patient chromosomes, and ii) said corresponding at least one of said twenty-two autosome human non-aneuploid chromosomes comprises all twenty-two autosome human non-aneuploid chromosomes.
9. The method of claim 1 , wherein said plasma DNA is not ligated to adapters.
10. The method of claim 1 , wherein said normalized count of the number of sequenced amplicons at each position where they align to said reference set of all twenty-two autosome human non-aneuploid chromosomes, and wherein said expected distribution comprises corresponding Z-scores for said at least one of said twenty-two autosome human non-aneuploid chromosomes.
11. The method of claim 1 , wherein, in step e): i) said at least one of said twenty-two autosome patient chromosomes comprises chromosomes 21, 13 and 18, and ii) said corresponding at least one of said twenty-two autosome human non-aneuploid chromosomes comprises chromosomes 21, 13, and 18.
12. The method of claim 1 , wherein said plurality of amplicons comprise at least 18,484 non-identical amplicons.