Methods for simultaneous amplification of target loci
The invention provides methods for simultaneously amplifying multiple nucleic acid regions of interest in one reaction volume as well as methods for selecting a library of primers for use in such amplification methods. The invention also provides library of primers with desirable characteristics, such as minimal formation of amplified primer dimers or other non-target amplicons.
1. A method for preparing a biological sample containing DNA from a first individual and a second individual, comprising:
isolating cell-free DNA from the biological sample, wherein the isolated cell-free DNA comprises the DNA from the first individual and DNA from the second individual;
amplifying the isolated cell-free DNA at a plurality of polymorphic loci on one or more chromosomes expected to be disomic, wherein the plurality of polymorphic loci comprises between 200 and 1,000 polymorphic loci, wherein the amplifying comprises amplifying the between 200 and 1,000 polymorphic loci from the cell-free DNA isolated from the biological sample using between 200 and 1,000 distinct primer pairs configure to target the between 200 and 1,000 polymorphic loci in a single reaction volume; and
preparing the isolated cell-free DNA amplified at the polymorphic loci for sequencing.
2. The method of claim 1 , wherein the method further comprises enriching the DNA in the sample at the plurality of polymorphic loci prior to the amplifying step.
3. The method of claim 2 , wherein the enrichment comprises:
obtaining a plurality of target-specific primers designed to hybridize to regions of DNA upstream and downstream of the polymorphic loci;
hybridizing the target-specific primers to the DNA; and
amplifying the DNA using the polymerase chain reaction to form amplicons.
4. The method of claim 2 , wherein the enrichment comprises preferentially enriching the DNA at the plurality of loci to minimize an average degree of allelic bias.
5. The method of claim 1 , wherein the polymorphic loci are SNP loci.
6. The method of claim 5 , wherein the polymorphic loci comprise SNP loci on chromosome 1.
7. The method of claim 5 , wherein the polymorphic loci comprise SNP loci on chromosome 2.
8. The method of claim 5 , wherein the polymorphic loci comprise SNP loci on chromosome 3.
9. The method of claim 1 , wherein sequencing comprises high-throughput sequencing.
10. The method of claim 1 , wherein the cell-free DNA comprises DNA from a fetus or a transplant.
11. The method of claim 1 , wherein the biological sample is a blood sample.
12. The method of claim 1 , wherein the distinct primers are circularizing probes.
13. The method of claim 1 , wherein the distinct primers are configured to target the polymorphic loci via hybridization.
14. The method of claim 1 , wherein the distinct primers comprise PCR primers.
15. The method of claim 1 , wherein the total amount of cfDNA in the sample is between 10 pg and 100 pg.
16. The method of claim 15 , wherein less than or equal to 10, 5, 2, 1, 0.5, 0.1, 0.05, 0.01, or 0.005% of the cfDNA molecules that have a first locus have a mutation in the first locus.
17. The method of claim 15 , wherein amplifying the isolated cell-free DNA comprises amplifying from 72%, 69%, 66%, 63%, 59%, or 56% of available cfDNA template fragment molecules.