Detecting mutations and ploidy in chromosomal segments
The invention provides methods, systems, and computer readable medium for detecting ploidy of chromosome segments or entire chromosomes, for detecting single nucleotide variants and for detecting both ploidy of chromosome segments and single nucleotide variants. In some aspects, the invention provides methods, systems, and computer readable medium for detecting cancer or a chromosomal abnormality in a gestating fetus.
1. A method for preparing a preparation of amplified DNA from a circulating DNA sample of an individual suspected of having cancer useful for detecting the presence of a copy number variation (CNV) in the circulating DNA sample of the individual, the method comprising:
(a) isolating circulating DNA from a blood sample, serum sample, or plasma sample from an individual suspected of having cancer;
(b) isolating cellular DNA from a second sample from the individual;
(c) preparing a preparation of amplified DNA by performing targeted multiplex amplification on the circulating DNA obtained in (a) and the cellular DNA obtained in (b) to amplify a set of at least 100 polymorphic loci relating to cancer-associated CNVs to obtain amplicons; and
(d) analyzing the preparation of amplified DNA obtained in (c) by:
sequencing the amplicons to determine allele frequencies in the samples, comprising the amount of each allele present in the sample at each locus in the set of polymorphic loci;
generating phased allelic information for the set of polymorphic loci in the circulating DNA by estimating the phase of the alleles of the circulating DNA; and
detecting the presence of a CNV in the circulating DNA sample using the allele frequencies and the phased allelic information for the set of polymorphic loci in the circulating DNA.
2. The method of claim 1 , wherein the second sample comprises a haploid cell and the isolated cellular DNA comprises DNA from the haploid cell.
3. The method of claim 2 , wherein the haploid cell is a sperm or an egg.
4. The method of claim 1 , wherein the second sample comprises a tumor cell and the isolated cellular DNA comprises DNA from the tumor cell.
5. The method of claim 1 , wherein a bioinformatics method is used to generate phased allelic information for the set of polymorphic loci in the circulating DNA, wherein the bioinformatics method uses population based haplotype frequencies to infer the most likely phase.
6. The method of claim 1 , wherein a molecular biology method is used to determine phased allelic information for the set of polymorphic loci in the cellular DNA, wherein the molecular biology method is used to obtain actual phased data.
7. The method of claim 1 , wherein a bioinformatics method is used to generate phased allelic information for the set of polymorphic loci in the circulating DNA and a molecular biology method is used to determine phased allelic information for the set of polymorphic loci in the cellular DNA, wherein the bioinformatics method uses population based haplotype frequencies to infer the most likely phase, and wherein the molecular biology method is used to obtain actual phased data.
8. The method of claim 1 , wherein the sequencing of amplicons obtained from the cellular DNA is performed using long read sequencing.
9. The method of claim 8 , wherein fragmented DNA derived from the cellular DNA is barcoded before sequencing the barcoded fragments or DNA derived therefrom.
10. The method of claim 1 , wherein the set of polymorphic loci comprises at least 1,000 polymorphic loci.
11. The method of claim 1 , wherein the method comprises using the allele frequencies and the phased allelic information for the set of polymorphic loci in the circulating DNA to determine an average allelic imbalance of the circulating DNA and using the average allelic imbalance to detect the presence of a CNV in the circulating DNA.
12. The method of claim 11 , wherein an average allelic imbalance equal to or greater than 0.5 in the circulating DNA is indicative of the presence of a CNV in the circulating DNA.
13. The method of claim 1 , wherein the method further comprises, before detecting the presence of a CNV in the sample:
generating individual probabilities of allele frequencies for the circulating DNA for the polymorphic loci for different ploidy states using the allele frequencies, wherein the individual probabilities are generated using a set of models of both different ploidy states and allelic imbalance fractions for the set of polymorphic loci;
generating joint probabilities for the set of polymorphic loci using the individual probabilities and the phased allelic information for the set of polymorphic loci in the circulating DNA; and
selecting, based on the joint probabilities, a best fit model indicative of chromosomal ploidy.
14. A method for preparing a preparation of amplified DNA from a circulating DNA sample of an individual suspected of having cancer useful for detecting the presence of a copy number variation (CNV) in the circulating DNA sample of the individual, the method comprising:
(a) isolating circulating DNA from a blood sample, serum sample, or plasma sample from an individual suspected of having cancer;
(b) isolating cellular DNA from a second sample from the individual, wherein the second sample comprises a haploid cell and the isolated cellular DNA comprises DNA from the haploid cell;
(c) preparing a preparation of amplified DNA by performing targeted multiplex amplification on the circulating DNA obtained in (a) and the cellular DNA obtained in (b) to amplify a set of at least 1,000 polymorphic loci relating to cancer-associated CNVs to obtain amplicons; and
d) analyzing the preparation of amplified DNA obtained in (c) by:
sequencing the amplicons to determine allele frequencies in the samples, comprising the amount of each allele present in the sample at each locus in the set of polymorphic loci, wherein the sequencing of amplicons obtained from the cellular DNA is performed using long read sequencing;
generating phased allelic information for the set of polymorphic loci in the circulating DNA by estimating the phase of the alleles of the circulating DNA; and
detecting the presence of a CNV in the circulating DNA sample using the allele frequencies and the phased allelic information for the set of polymorphic loci in the circulating DNA.
15. The method of claim 14 , wherein the haploid cell is a sperm or an egg.
16. The method of claim 14 , wherein a bioinformatics method is used to generate phased allelic information for the set of polymorphic loci in the circulating DNA and a molecular biology method is used to determine phased allelic information for the set of polymorphic loci in the cellular DNA, wherein the bioinformatics method uses population based haplotype frequencies to infer the most likely phase, and wherein the molecular biology method is used to obtain actual phased data.
17. The method of claim 14 , wherein fragmented DNA derived from the cellular DNA is barcoded before sequencing the barcoded fragments or DNA derived therefrom.
18. The method of claim 14 , wherein the method comprises using the allele frequencies and the phased allelic information for the set of polymorphic loci in the circulating DNA to determine an average allelic imbalance of the circulating DNA and using the average allelic imbalance to detect the presence of a CNV in the circulating DNA.
19. The method of claim 18 , wherein an average allelic imbalance equal to or greater than 0.5 in the circulating DNA is indicative of the presence of a CNV in the circulating DNA.
20. The method of claim 14 , wherein the method further comprises, before detecting the presence of a CNV in the sample:
generating individual probabilities of allele frequencies for the circulating DNA for the polymorphic loci for different ploidy states using the allele frequencies, wherein the individual probabilities are generated using a set of models of both different ploidy states and allelic imbalance fractions for the set of polymorphic loci;
generating joint probabilities for the set of polymorphic loci using the individual probabilities and the phased allelic information for the set of polymorphic loci in the circulating DNA; and
selecting, based on the joint probabilities, a best fit model indicative of chromosomal ploidy.