Screening for structural variants
The invention relates to carrier screening and methods for describing a structural variant, such as a large rearrangement or chromosomal abnormality, in a person's genome using probes that are designed to determine the person's genetic sequence and reveal substitution mutations and small structural variants. Identifying a structural variant may include exposing a nucleic acid to a plurality of probes. Each probe has a linked pair of targeting arms designed to hybridize upstream and downstream of a target in a genome. The method includes hybridizing two of the probes to the nucleic acid and attaching the two probes together to create an inter-probe product as well as detecting the inter-probe product and reporting a structural variant of the genome in the nucleic acid.
1. A nucleic acid product comprising:
a first molecular inversion probe comprising a linked pair of targeting arms designed to hybridize upstream and downstream of a first target in a reference genome;
a second molecular inversion probe comprising a linked pair of targeting arms designed to hybridize upstream and downstream of a second target in a reference genome, wherein the first and second targets are noncontiguous; and
an inter-probe region connecting one of the targeting arms of the first molecular inversion probe with one of the targeting arms of the second molecular inversion probe, wherein the second molecular inversion probe and the inter-probe region have been ligated to the first molecular inversion probe to form an inter-probe product;
wherein at least one of the first and second molecular inversion probes comprises a phosphorothioate base.
2. The nucleic acid product of claim 1 , wherein the targeting arms of each molecular inversion probe are configured to hybridize to nucleic acid residues on a same strand of the reference genome.
3. The nucleic acid product of claim 1 , wherein the inter-probe region comprises nucleic acid sequence spanning a structural variant on a target nucleic acid.
4. The nucleic acid product of claim 3 , wherein the inter-probe region comprises nucleic acid sequence formed by filling in a gap between the two molecular inversion probes along the target nucleic acid using a polymerase.
5. The nucleic acid product of claim 3 , wherein the structural variant comprises an insertion, inversion, translocation, or deletion.
6. The nucleic acid product of claim 1 , wherein the phosphorothioate base is located in a backbone of the first or second molecular inversion probes.
7. The nucleic acid product of claim 1 , wherein the phosphorothioate base is located on the first molecular inversion probe.
8. The nucleic acid product of claim 1 , wherein the phosphorothioate base is located on the second molecular inversion probe.
9. The nucleic acid product of claim 1 , wherein each of the first and second molecular inversion probes comprises a phosphorothioate base.
10. A probe set comprising a plurality of different molecular inversion probes, each different molecular inversion probe comprising:
a first targeting arm configured to hybridize upstream of a target in a reference genome;
a second targeting arm configured to hybridize downstream of a target in a reference genome; and
a central region flanked by the first and second targeting arms, the central region comprising a phosphorothioate base,
wherein the target of each different molecular inversion probe is a different location on the reference genome,
wherein two molecular inversion probes that hybridize by only one targeting arm have been ligated together by their targeting arms into an inter-probe product.
11. The probe set of claim 10 , wherein the plurality of molecular inversion probes are configured to tile across the reference genome with each target overlapping with at least one other target on the reference genome.
12. The probe set of claim 10 , wherein the first and second targeting arms of each molecular inversion probe hybridize to nucleic acid residues on a same strand of the reference genome.
13. The probe set of claim 10 , wherein each molecular inversion probe is configured to covalently close when hybridized to the reference genome by both targeting arms.
14. An inter-probe product nucleic acid molecule comprising:
a first molecular inversion probe comprising a first 5′ targeting arm a first 3′ targeting arm; and
a second molecular inversion probe comprising a second 5′ targeting arm and a second 3′ targeting arm, wherein the second 3′ targeting arm is ligated to the first 5′ targeting arm.
15. The nucleic acid molecule of claim 14 , wherein the first molecular inversion probe is ligated to the second molecular inversion probe via an extension segment synthesized by a polymerase when the first molecular inversion probe and the second molecular inversion probe were each hybridized to a target by only one probe arm.
16. The nucleic acid molecule of claim 14 , wherein the second 3′ targeting arm was ligated to the first 5′ targeting arm due to the presence of a structural variant.
17. The nucleic acid molecule of claim 16 , wherein the structural variant comprises a deletion.
18. The nucleic acid molecule of claim 15 , wherein the nucleic acid molecule is present among a plurality of probes including the nucleic acid molecule and a plurality of molecular inversion probes that each have been circularized and include a copy of a portion of the target.
19. The nucleic acid molecule of claim 18 , wherein the plurality of probes are useful in a carrier screening assay that can report on variants in a genome of a patient, wherein the reported variants include mutations, short indels between about 1 and tens of base pairs, large deletions.
20. The nucleic acid molecule of claim 18 , wherein the plurality of molecular inversion of probes, after being circularized, have been cleaved into linear fragments and attached to barcodes and sequencing adaptors, and further wherein the plurality of probes are attached to the surface of flow cell channels.