Multiplexed method for the identification and quantitation of minor alleles and polymorphisms

• US 10,513,728 B2
• Filed: 01/23/2019
• Issued: 12/24/2019
• Est. Priority Date: 04/24/2015
• Status: Active Grant

• Current Assignee: Agena Bioscience Inc. (Mesa Laboratories Inc.)
• Original Assignee: Agena Bioscience Inc. (Mesa Laboratories Inc.)
• Inventors: Nygren, Anders Olof Herman
• Primary Examiner(s): Horlick, Kenneth R
• Application Number:
  US16/255,718
• Publication Number:
  US 20190153526A1
• Time in Patent Office: 335 Days
• Field of Search: None
• CPC Class Codes: C12Q 1/6827 for detection of mutation or polymorphism
• CPC Class Codes: C12Q 1/6858 Allele-specific amplification
• CPC Class Codes: C12Q 1/686 Polymerase chain reaction [PCR]
• CPC Class Codes: C12Q 2525/186 incorporating a non-extendable or blocking moiety
• CPC Class Codes: C12Q 2527/137 Concentration of a component of medium
• CPC Class Codes: C12Q 2535/125 Allele specific primer extension
• CPC Class Codes: C12Q 2537/143 Multiplexing, i.e. use of multiple primers or probes in a single reaction, usually for simultaneously analyse of multiple analysis
• CPC Class Codes: C12Q 2545/101 with an internal standard/control

Abstract

Provided herein are products and processes for detecting the presence or absence of minor nucleic acid species in a sample containing a mixture of minor nucleic acid species and one or more major nucleic acid species, where the amount (frequency or copy number) of the minor nucleic acid species is less than that of the major nucleic acid species. Certain methods include amplifying the mixture and extending the resulting amplicons using chain terminating reagents and extension primers that specifically hybridize to the amplicons, where a chain terminating reagent specific for the major nucleic acid species has a concentration that is less than a chain terminating reagent that is specific for a minor nucleic acid species. Skewing the concentrations of the chain terminating reagents in favor of high concentrations of the chain terminating reagents specific for the minor nucleic acid species relative to a chain terminating reagent specific for a major nucleic acid species improves the detection limit (sensitivity) of detecting minor nucleic acid species present at low frequency or copy number in the mixture. In addition, the signals generated from the extension product of the major nucleic acid species amplicon can serve as a positive control and permit quantification of the minor nucleic acid species relative to the major nucleic acid species in the mixture.

Claims

1. A method for quantifying one or more minor nucleic acid species in a nucleic acid population comprising a mixture of the one or more minor nucleic acid species and a major nucleic acid species, wherein the minor nucleic acid species are variants of the same major nucleic acid species and are each present in a copy number that is less than the copy number of the major nucleic acid species, the method comprising:

(a) amplifying target regions of the mixture with amplification primer pairs under amplification conditions comprising dNTPs, whereby an amplified mixture of nucleic acids comprising major and minor nucleic acid species is produced;

(b) contacting the amplified mixture with extension primers under extension conditions comprising chain terminating reagents specific for (i) each of the one or more minor nucleic acid species, and (ii) the major nucleic acid species, whereby the primers are extended up to the nucleotide positions that are different in the minor nucleic acid species relative to the major nucleic acid species, thereby generating chain terminated extension products corresponding to the minor nucleic acid species and the major nucleic acid species, respectively, wherein;

(1) the concentrations of each of the chain terminating reagents are known; and

(2) the concentration of the chain terminating reagent specific for the major nucleic acid species is less than the concentration(s) of the chain terminating reagent(s) specific for the one or more minor nucleic acid species;

(c) determining the ratio of the amount(s) of extension products corresponding to each of the one or more minor nucleic acid species relative to the amount of extension product corresponding to the major nucleic acid species; and

(d) based on the ratio of (c), and based on the concentration(s) of the chain terminating reagents specific for the one or more minor nucleic acid species relative to the concentration of the chain terminating reagent specific for the major nucleic acid species, quantifying the amount(s) of minor nucleic acid species relative to the amount of the major nucleic acid species.

2. The method of claim 1, wherein the nucleic acid population comprises a plurality of minor nucleic acid species that are variants of a single major nucleic acid species and the plurality of minor nucleic acid species are identified in a single, multiplexed reaction.

3. The method of claim 1, wherein the sequences of the minor and major nucleic acid species differ by a single base and the primers are extended up the single base that is different.

4. The method of claim 1, wherein the sequence of the minor nucleic acid species comprises an insertion or a deletion relative to the sequence of the major nucleic acid species.

5. The method of claim 1, wherein the minor and major nucleic acid species are mutant and wild type alleles, respectively, of the same gene.

6. The method of claim 1, wherein the one or more minor nucleic acid species are each present in a copy number that is between about 1% to less than 10% of the copy number of the major nucleic acid species.

7. The method of claim 1, wherein the concentration of the chain terminating reagent specific for the major nucleic acid species is between about 0.01% to about 10% of the concentration of each of the chain terminating reagent(s) specific for the minor nucleic acid species.

8. The method of claim 1, wherein the concentration of the chain terminating reagent for the major nucleic acid species varies based on the specific major species/minor species transition.

9. The method of claim 1, wherein the chain terminating reagents are chain terminating nucleotides.

10. The method of claim 9, wherein the chain terminating nucleotides independently are selected from among ddATP, ddGTP, ddCTP, ddTTP and ddUTP.

11. The method of claim 9, wherein the chain terminating nucleotides specific for one or more of the minor nucleic acid species consist of one chain terminating nucleotide.

12. The method of claim 9, wherein the chain terminating nucleotides specific for one or more of the minor nucleic acid species consist of two chain terminating nucleotides.

13. The method of claim 9, wherein the chain terminating nucleotides specific for one or more of the minor nucleic acid species consist of three chain terminating nucleotides.

14. The method of claim 1, wherein the chain terminating reagents comprise one or more acyclic terminators.

15. The method of claim 1, wherein one or more of the chain terminating reagents comprises a detectable label.

16. The method of claim 15, further comprising detection of the label, whereby the one or more minor nucleic acid species are quantified.

17. The method of claim 16, wherein the label is a mass label and detection is by mass spectrometry.

18. The method of claim 16, wherein the label is a fluorescent label or dye and detection is by electrophoresis or real time PCR.