Methods and systems for analyzing guide RNA molecules

1. A method of assessing a sample of guide RNA molecules, comprising:

(a) determining the nucleotide sequences of a plurality of guide RNA molecules of the sample, wherein the step of determining comprises combining:

(i) the plurality of guide RNA molecules;

(ii) one or more template switching oligonucleotides comprising a 3′ hybridization domain and a sequence adapter;

(iii) a retroviral reverse transcriptase; and

(iv) dNTPs;

(b) comparing the nucleotide sequences of the plurality of guide RNA molecules to a reference guide RNA sequence to identify truncation variants and/or sequence variants, relative to the reference guide RNA sequence;

(c) determining a level of truncation variants comprising a truncation, relative to the reference guide RNA sequence;

(d) determining a level of sequence variants comprising one or more of a nucleotide substitution, insertion or deletion, relative to the reference guide RNA sequence, within the 100 nucleotides proximate to a 5′ end of the reference guide RNA sequence and/or within a bulge region of the reference guide RNA sequence and/or within a nexus region of the reference guide RNA sequence; and

(e) for each sequence variant guide RNA molecule present at a level greater than or equal to 0.1%,

(i) identifying the nucleotide sequence of the targeting domain of the sequence variant; and

(ii) determining one or more potential off-target sites for the targeting domain of the sequence variant.

2. The method of claim 1 , wherein the guide RNA molecules and the reference guide RNA sequence comprise a targeting domain within the first 30 nucleotides.

3. The method of claim 1 , comprising determining the level of sequence variants comprising one or more of a nucleotide substitution, insertion or deletion within the nexus region, relative to the reference guide RNA sequence.

4. The method of claim 1 , comprising determining the level of sequence variants comprising one or more of a nucleotide substitution, insertion or deletion within the bulge region, relative to the reference guide RNA sequence.

5. The method of claim 1 , further comprising assigning a value to the sample of guide RNA molecules based on the determined level of truncation variants and/or sequence variants.

6. The method of claim 1 , further comprising assigning a mismatch frequency to the sample of guide RNA molecules based on the determined level of truncation variants and/or sequence variants.

7. The method of claim 1 ,

comprising combining (i)-(iv) in a reaction mixture under conditions sufficient to produce a plurality of product nucleic acids, each product nucleic acid comprising (i) a guide RNA molecule and (ii) the one or more template switching oligonucleotides, each hybridized to adjacent regions of a single product nucleic acid comprising a region polymerized from the dNTPs by the retroviral reverse transcriptase, wherein the region polymerized from the dNTPs comprises a domain that is complementary to and hybridized to the 5′ end of the guide RNA molecule.

8. The method of claim 1 , wherein the guide RNA molecules are non-polyadenylated, and the method further comprises polyadenylating the 3′ ends of the non-polyadenylated guide RNA molecules.

9. The method of claim 7 , wherein the 3′ hybridization domain comprises a homo-trinucleotide.

10. The method of claim 9 , wherein the homo-trinucleotide comprises guanine nucleotides.

11. The method of claim 9 , wherein the method comprises combining:

the plurality of guide RNA molecules; and

a heterogeneous mixture of template switching oligonucleotides comprising a 3′ hybridization domain and a sequence adapter and wherein the 3′ hybridization domains comprise a partially degenerate sequence of guanine nucleotides and cytosine nucleotides (SSS).

12. The method of claim 9 , wherein the one or more template switching oligonucleotides comprise a 5′ domain comprising one or more isomers of guanine nucleotides or cytosine nucleotides.

13. The method of claim 9 , wherein the one or more template switching oligonucleotides comprise a unique molecular identifier.

14. The method of claim 1 , wherein the sequence adapter comprises a nucleic acid domain selected from the group consisting of a domain that specifically binds to a surface-attached sequencing oligonucleotide, a sequencing primer binding domain, a barcode domain, a barcode sequencing primer binding domain, a molecular identification domain, and a combination thereof.

15. The method of claim 13 , wherein the identifying steps and/or determining steps comprise identifying the unique molecular identifier.

16. The method of claim 9 , further comprising contacting a 3′ region of the single product nucleic acid complementary to the one or more template switching oligonucleotides with a second strand primer configured to bind thereto under hybridization conditions.

17. The method of claim 9 , further comprising contacting the guide RNA molecules with a first primer that primes the synthesis of the single product nucleic acid.

18. The method of claim 7 , further comprising subjecting the single product nucleic acid to nucleic acid amplification conditions.

19. The method of claim 1 , wherein the guide RNA molecules comprise a 5′ modification.