Systems and methods to detect rare mutations and copy number variation
The present disclosure provides a system and method for the detection of rare mutations and copy number variations in cell free polynucleotides. Generally, the systems and methods comprise sample preparation, or the extraction and isolation of cell free polynucleotide sequences from a bodily fluid; subsequent sequencing of cell free polynucleotides by techniques known in the art; and application of bioinformatics tools to detect rare mutations and copy number variations as compared to a reference. The systems and methods also may contain a database or collection of different rare mutations or copy number variation profiles of different diseases, to be used as additional references in aiding detection of rare mutations, copy number variation profiling or general genetic profiling of a disease.
1. A method for detecting copy number variation, comprising:
a) sequencing extracellular polynucleotides from a bodily sample from a subject, wherein each of the extracellular polynucleotides generates a plurality of sequence reads;
b) filtering out reads that fail to meet a set accuracy, quality score, or mapping score threshold;
c) mapping the plurality of sequence reads to a reference sequence;
d) quantifying mapped reads or unique sequence reads in a plurality of predefined regions of the reference sequence; and
e) determining copy number variation in one or more of the plurality of predefined regions by:
i) normalizing a number of reads in the plurality of predefined regions to each other, or a number of unique sequence reads in the plurality of predefined regions to each other; and/or
ii) processing a number of reads in the plurality of predefined regions or a number of unique sequence reads in the plurality of predefined regions with numbers obtained from a control sample.
2. The method of claim 1 , further comprising isolating extracellular polynucleotides from the bodily sample.
3. The method of claim 1 , further comprising generating copies of the extracellular polynucleotides prior to sequencing.
4. The method of claim 1 , further comprising determining a percent of sequences having copy number variation or rare mutation or variant in the bodily sample.
5. The method of claim 1 , further comprising attaching one or more barcodes to the extracellular polynucleotides or fragments thereof prior to sequencing.
6. The method of claim 5 , wherein each barcode attached to the extracellular polynucleotides or fragments thereof prior to sequencing is not unique.
7. The method of claim 5 , wherein each barcode comprises a fixed or semi-random oligonucleotide sequence that in combination with a diversity of molecules sequenced from a selected region enables identification of unique molecules.
8. The method of claim 1 , further comprising selectively enriching regions from a genome or transcriptome of the subject prior to sequencing.
9. The method of claim 1 , further comprising attaching one or more barcodes to the extracellular polynucleotides or fragments thereof prior to an amplification or enrichment step.
10. A method for detecting a rare mutation in a cell-free or substantially cell-free sample obtained from a subject, comprising:
a) sequencing extracellular polynucleotides from a bodily sample from the subject, wherein each of the extracellular polynucleotides generates a plurality of sequence reads;
b) filtering out reads that fail to meet a set accuracy, quality score, or mapping score threshold;
c) mapping sequence reads derived from the sequencing onto a reference sequence;
d) determining unique sequence reads corresponding to the extracellular polynucleotides from among the sequence reads;
e) identifying a subset of mapped unique sequence reads that include a variant as compared to the reference sequence at each mappable base position;
f) for each mappable base position, calculating a ratio of (a) a number of mapped unique sequence reads that include a variant as compared to the reference sequence, to (b) a number of total unique sequence reads for each mappable base position; and
g) processing the ratio with a similarly derived number from a reference sample.
11. The method of claim 10 , further comprising isolating extracellular polynucleotides from the bodily sample.
12. The method of claim 10 , further comprising generating copies of the extracellular polynucleotides prior to sequencing.
13. The method of claim 10 , further comprising determining a percent of sequences having copy number variation or rare mutation or variant in the bodily sample.
14. The method of claim 13 , wherein the determining comprises calculating a percent of predefined regions with an amount of polynucleotides above or below a threshold.
15. The method of claim 10 , further comprising attaching one or more barcodes to the extracellular polynucleotides or fragments thereof prior to sequencing.
16. The method of claim 15 , wherein each barcode attached to the extracellular polynucleotides or fragments thereof prior to sequencing is not unique.
17. The method of claim 15 , wherein each barcode comprises a fixed or semi-random oligonucleotide sequence that in combination with a diversity of molecules sequenced from a selected region enables identification of unique molecules.
18. The method of claim 10 , further comprising selectively enriching regions from a genome or transcriptome of the subject prior to sequencing.
19. The method of claim 10 , further comprising attaching one or more barcodes to the extracellular polynucleotides or fragments thereof prior to an amplification or enrichment step.
20. The method of claim 1 , wherein each of the plurality of predefined regions is a single base.
21. The method of claim 10 , wherein the each mappable base position is a single mappable base position.
22. The method of claim 1 , wherein e) comprises i) and ii).
23. The method of claim 1 , wherein e) comprises i) normalizing the number of reads in the plurality of predefined regions to each other.
24. The method of claim 1 , wherein e) comprises i) normalizing the number of unique sequence reads in the plurality of predefined regions to each other.
25. The method of claim 1 , wherein e) comprises ii) processing the number of reads in the plurality of predefined regions with numbers obtained from the control sample.
26. The method of claim 1 , wherein e) comprises ii) processing the number of unique sequence reads in the plurality of predefined regions with numbers obtained from the control sample.