Methods for selectively suppressing non-target sequences
The invention generally relates to negative selection of nucleic acids. The invention provides methods and systems that remove unwanted segments of nucleic acid in a sample so that a target gene or region of interest may be analyzed without interference from the unwanted segments. A sample is obtained that includes single-stranded nucleic acid with one or more unwanted segments. Complementary nucleic acid is added to the single-stranded nucleic acid to create a double-stranded region that includes the unwanted segment. The double-stranded region is then digested, leaving single-stranded nucleic acid that includes the target gene or region of interest. This allows paralogs, pseudogenes, repetitive elements, and other segments of the genome that may be similar to the target gene or region of interest to be removed from the sample.
1. A method of removing a paralog of a gene of interest in a nucleic acid from a sample, the method comprising:
obtaining a single-stranded nucleic acid that contains a gene of interest and a paralog of the gene of interest;
annealing an oligonucleotide to a portion of the single-stranded nucleic acid that flanks the paralog of the gene of interest; and
extending the annealed oligonucleotide to create a double-stranded region that contains the paralog of the gene of interest;
removing the paralog of the gene of interest by digesting the double-stranded region, thereby leaving only intact genomic DNA including the gene of interest;
performing a molecular inversion probe capture assay on the intact genomic DNA; and
sequencing the gene of interest.
2. The method of claim 1 , wherein the extending step is conducted using a polymerase enzyme under conditions sufficient to cause extension of the primer in a template-dependent manner.
3. The method of claim 1 , wherein the digesting step comprising exposing the sample to an enzyme that preferentially digests double-stranded nucleic acid.
4. The method of claim 3 , wherein the enzyme is selected from double-stranded endonucleases, restriction endonucleases, and nicking enzymes.
5. The method of claim 4 , further comprising the step of deactivating the enzyme.
6. The method of claim 1 , wherein the sequencing is Next Generation Sequencing.
7. The method of claim 1 , further comprising the step of obtaining a sample from a subject and denaturing double-stranded DNA in the sample.
8. The method of claim 7 , wherein the denaturing step comprises exposing the sample to heat, a detergent, or a basic solution.
9. The method of claim 1 , wherein the gene comprises survival of motor neuron 1 (SMN1) and the paralog targeted for removal is survival of motor neuron 2 (SMN2).
10. The method of claim 9 , wherein the sequencing step further comprises detection of a spinal muscular atrophy (SMA) mutation.
11. A method of sequencing a gene of interest, the method comprising:
obtaining a single-stranded nucleic acid that contains a gene of interest and a pseudogene of the gene of interest;
annealing an oligonucleotide to a portion of the single-stranded nucleic acid adjacent to the pseudogene of the gene of interest; and
extending the annealed oligonucleotide to create a double-stranded region that contains the pseudogene of the gene of interest;
removing the pseudogene of the gene of interest by digesting the double-stranded region, thereby leaving only intact genomic DNA including the gene of interest;
performing a molecular inversion probe capture assay on the intact genomic DNA; and
sequencing the gene of interest.
12. The method of claim 11 , wherein the gene comprises glucosidase beta acid (GBA).
13. The method of claim 12 , wherein the sequencing step further comprises detection of a Gaucher disease mutation.
14. The method of claim 11 , wherein the extending step is conducted using a polymerase enzyme under conditions sufficient to cause extension of the primer in a template-dependent manner.
15. The method of claim 11 , wherein the digesting step comprising exposing the sample to an enzyme that preferentially digests double-stranded nucleic acid.
16. The method of claim 11 , wherein the sequencing is Next Generation Sequencing.