Methods for identifying DNA copy number changes

Patent metadata

Field	Value
Publication number	US-10108777-B2
Application number	US-201213459603-A
Country	US
Kind code	B2
Filing date	Apr 30, 2012
Priority date	Nov 11, 2002
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

Methods of identifying allele-specific changes in genomic DNA copy number are disclosed. Methods for identifying homozygous deletions and genetic amplifications are disclosed. An array of probes designed to detect presence or absence of a plurality of different sequences is also disclosed. The probes are designed to hybridize to sequences that are predicted to be present in a reduced complexity sample. The methods may be used to detect copy number changes in cancerous tissue compared to normal tissue. The methods may be used to diagnose cancer and other diseases associated with chromosomal anomalies.

First claim

What is claimed is:

1. A method for estimating copy numbers using a high-density nucleic acid array having a plurality of allele-specific nucleic acid probes to single nucleotide polymorphisms (SNPs), and a computer system comprising at least one processor, a memory, and an interface, the method comprising:
conducting a reference assay using a first high-density microarray genotyping assay to hybridize a plurality of fragments amplified from a reference nucleic acid sample with a plurality of allele-specific perfect match nucleic acid probes in the high-density nucleic acid array, wherein each of the plurality of allele-specific perfect match probes are complementary to individual alleles of a SNP, and wherein conducting the reference assay generates reference data by:
measuring raw probe intensity data comprising observed intensity measurements for each probe;
applying a log-based transformation of the raw probe intensity data for the SNPs;
performing a standardization of the log-based transformation of the raw probe intensity data based on background intensity signals measured from a plurality of background probes to establish comparability across samples;
identifying, using a target set of allelic copy numbers, a plurality of sets of nucleic acid probes by calculating a linear correlation between the standardized log-based transformation of the raw probe intensity data, and the copy numbers from the target set of allelic copy numbers,
and selecting for the plurality of sets of nucleic acid probes, those sets of probes that have a linear correlation that meets or exceeds a threshold amount;

determining and storing in the computer system a plurality of allele-specific reference models of allele-specific relationships between copy number and standarized log-based transformation of the raw probe intensity data of the selected plurality of sets of nucleic acid probes for the reference assay;
conducting an experimental assay using the first high-density microarray genotyping assay to hybridize a plurality of fragments amplified from an experimental nucleic acid sample with the selected plurality of sets of nucleic acid probes to generate experimental data including raw experimental probe intensity data comprising observed intensity measurements for the selected plurality of sets of nucleic acid probes; and
using the computer system to process the experimental data to genotype and determine estimated copy numbers for a plurality of alleles by applying respective allele-specific reference models corresponding to the selected plurality of sets of nucleic acid probes to respective portions of the raw experimental probe intensity data that correspond to the selected plurality of sets of nucleic acid probes.

2. The method of claim 1 , wherein the threshold amount of linear correlation is 0.6.

3. The method of claim 1 , further comprising determining estimated copy numbers only for SNPs that have at least one selected nucleic acid probe for each of the plurality of different alleles.

4. The method of claim 1 , wherein applying a log-based transformation of the raw probe intensity data for the SNPs comprises calculating the logarithm of each of the observed intensity measurements, and wherein the observed intensity measurements are based on fluorescent intensities obtained from scanning the nucleic acid sample hybridized with the plurality of allele-specific nucleic acid probes.

5. The method of claim 1 , further comprising: measuring a GC content and a restriction fragment length of each of the plurality of sets of nucleic acid probes and applying a linear regression analysis to reduce intensity measurement variability, wherein the GC content of the plurality of sets of nucleic acid probes contributes to the intensity measurement variability.

6. The method of claim 5 , wherein conducting an experimental assay further comprises:
genotyping the experimental nucleic acid sample, wherein genotyping comprises generating SNP genotype data of the experimental nucleic acid sample; and
regressing raw experimental probe intensity data corresponding to the selected plurality of sets of nucleic acid probes against at least one mean reference intensity of the allele-specific reference model for one or more intensity measurements associated with alleles which possess a same genotype within the experimental assay as in the reference assay.

7. The method of claim 1 , wherein at least one SNP is located within at least one of a plurality of genomic regions.

8. The method of claim 7 , further comprising estimating a total copy number for each of the plurality of genomic regions by summing the estimated copy numbers for each of the plurality of alleles for the at least one SNP.

9. The method of claim 1 , further comprising:
analyzing the estimated copy numbers for each of the plurality of alleles to calculate significance values; and
applying kernel smoothing to both the estimated copy numbers and the significance values to generate smoothed copy numbers and smoothed significance values.

10. The method of claim 1 , further comprising:
fragmenting nucleic acids from the experimental nucleic acid sample with a restriction enzyme to generate nucleic acid fragments;
ligating an adaptor to the nucleic acid fragments to generate adaptor ligated fragments;
amplifying at least some of the adaptor ligated fragments to generate amplicons; and
labeling the amplicons to generate labeled amplicons, wherein at least one of the labeled amplicons is hybridized to the high density nucleic acid array.

11. The method of claim 1 , wherein the high-density nucleic acid array comprises a plurality of perfect match probes for a first allele of a single nucleotide polymorphism (SNP), a plurality of perfect match probes for a second allele of the SNP, a plurality of mismatch probes for the first allele of the SNP, and a plurality of mismatch probes for the second allele of the SNP.

12. The method of claim 1 , wherein the reference nucleic acid sample comprises at least one of normal samples without copy number changes and tumor samples with copy number changes.

13. The method of claim 1 , wherein conducting the reference and experimental assays generates and applies allele-specific reference models for genotypes of more than 10,000, more than 100,000, or more than 500,000 SNPs in a single experiment.

14. A method for estimating copy numbers using a high-density nucleic acid array having a plurality of allele-specific nucleic acid probes to single nucleotide polymorphisms (SNPs), and a computer system comprising at least one processor, a memory, and an interface, the method comprising:
conducting an experimental assay using a first high-density microarray genotyping assay to hybridize a plurality of fragments amplified from an experimental nucleic acid sample with the selected plurality of sets of nucleic acid probes to generate experimental data including experimental probe intensity data comprising observed intensity measurements of hybridization for the selected plurality of sets of nucleic acid probes; and
using the computer system to process the experimental data to genotype and determine estimated copy numbers for a plurality of alleles by applying respective allele-specific reference models of the selected plurality of sets of nucleic acid probes to respective portions of the raw experimental probe intensity data that correspond to the selected plurality of sets of nucleic acid probes;
wherein the respective allele-specific reference models are stored in the computer system and are obtained by:
conducting the reference assay using the first high-density microarray genot

Assignees

• Huang Jing
• Jones Keith W
• Shapero Michael H
• Affymetrix Inc

Inventors

• Huang Jing
• Jones Keith W
• Shapero Michael H

Classifications

• C12Q1/6827

  for detection of mutation or polymorphism · CPC title

• G16B25/00

  ICT specially adapted for hybridisation; ICT specially adapted for gene or protein expression · CPC title

• C12Q1/6837

  using probe arrays or probe chips (C12Q1/6874 takes precedence) · CPC title

• G16B20/00 Primary

  ICT specially adapted for functional genomics or proteomics, e.g. genotype-phenotype associations · CPC title

• G06F19/18 Primary

  Physics · mapped topic