Cas variants for gene editing
Some aspects of this disclosure provide strategies, systems, reagents, methods, and kits that are useful for the targeted editing of nucleic acids, including editing a single site within the genome of a cell or subject, e.g., within the human genome. In some embodiments, fusion proteins of Cas9 and nucleic acid editing enzymes or enzyme domains, e.g., deaminase domains, are provided. In some embodiments, methods for targeted nucleic acid editing are provided. In some embodiments, reagents and kits for the generation of targeted nucleic acid editing proteins, e.g., fusion proteins of Cas9 and nucleic acid editing enzymes or domains, are provided.
1. A method of nucleic acid editing, the method comprising contacting a target nucleic acid molecule with the following:
(a) a cytidine deaminase,
(b) a Cas9 variant comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 37, or an amino acid sequence having at least 90% sequence identity with SEQ ID NO: 2 or SEQ ID NO: 37, wherein the Cas9 variant comprises one or more nuclease inactivating mutations within a RuvC1 subdomain and/or an HNH subdomain; and
(c) a guide RNA (sgRNA) comprising a region complementary to a strand of the target nucleic acid molecule, wherein the cytidine deaminase, target nucleic acid molecule, Cas9 variant, and guide RNA associate in a complex, and
wherein the method results in deamination of a cytidine in the target nucleic acid molecule.
2. The method of claim 1 , wherein the Cas9 variant comprises the inactivating mutation within the RuvC1 subdomain.
3. The method of claim 1 , wherein the inactivating mutation within the RuvC1 subdomain corresponds to a mutation at D10 in SEQ ID NO: 2.
4. The method of claim 1 , wherein the Cas9 variant comprises an amino acid sequence having at least 90% sequence identity with SEQ ID NO: 2.
5. The method of claim 1 , wherein the Cas9 variant comprises an amino acid sequence having at least 95% sequence identity with SEQ ID NO: 2.
6. The method of claim 1 , wherein the Cas9 variant comprises an amino acid sequence having at least 99% sequence identity with SEQ ID NO: 2.
7. The method of claim 1 , wherein the inactivating mutation within the RuvC1 subdomain corresponds to a D10A mutation in SEQ ID NO: 2.
8. The method of claim 1 , wherein the Cas9 variant comprises the inactivating mutation within the HNH subdomain.
9. The method of claim 1 , wherein the inactivating mutation within the HNH subdomain corresponds to a mutation at position H839 of SEQ ID NO: 2of.
10. The method of claim 1 , wherein the Cas9 variant comprises an amino acid sequence having at least 90% sequence identity with SEQ ID NO: 37.
11. The method of claim 1 , wherein the Cas9 variant comprises an amino acid sequence having at least 95% sequence identity with SEQ ID NO: 37.
12. The method of claim 1 , wherein the Cas9 variant comprises an amino acid sequence having at least 99% sequence identity with SEQ ID NO: 37.
13. The method of claim 1 , wherein the inactivating mutation within the HNH subdomain corresponds to an H839A mutation of SEQ ID NO: 2.
14. The method of claim 1 , wherein the cytidine deaminase is an apolipoprotein B mRNA-editing complex (APOBEC) family deaminase.
15. The method of claim 1 , wherein the cytidine deaminase is an APOBEC1 family deaminase.
16. The method of claim 1 , wherein the cytidine deaminase is an activation-induced cytidine deaminase (AID).
17. The method of claim 1 , wherein the cytidine deaminase is linked to the Cas9 variant by a linker.
18. The method of claim 17 , wherein the linker comprises a (GGGGS) n (SEQ ID NO: 91), a (G) n , an (EAAAK) n (SEQ ID NO: 5), or an (XP) n motif, or a combination of any of these, wherein n is independently an integer between 1 and 30.
19. The method of claim 1 , wherein the cytidine deaminase is linked to an N-terminus of the Cas9 variant.
20. The method of claim 1 , wherein the target nucleic acid molecule comprises a sequence associated with a disorder.
21. The method of claim 20 , wherein the sequence associated with the disorder encodes a protein, and wherein the deamination introduces a stop codon into the sequence associated with the disorder, resulting in a truncation of the encoded protein.
22. The method of claim 1 , wherein the deamination corrects a point mutation in the target nucleic acid molecule, wherein the point mutation is associated with a disorder.
23. The method of claim 22 , wherein the nucleic acid comprises a T to C point mutation, and wherein the deamination of the mutant C base results in a nucleic acid sequence that is not associated with the disorder.
24. The method of claim 22 , wherein the nucleic acid comprises an A to G point mutation, and wherein the deamination of the mutant G base results in a nucleic acid sequence that is not associated with the disorder.
25. The method of claim 1 , wherein the contacting occurs in vivo in a subject.
26. The method of claim 1 , wherein the cytidine deaminase comprises an amino acid sequence selected from the group consisting of: SEQ ID NO: 6 (human AID), SEQ ID NO: 7 (mouse AID), SEQ ID NO: 10 (mouse APOBEC-3), SEQ ID NO: 15 (human APOBEC-3), SEQ ID NO: 16 (human APOBEC-3F), SEQ ID NO: 17 (human APOBEC-3B), SEQ ID NO: 18 (human APOBEC-3C), SEQ ID NO: 19 (human APOBEC-3A), SEQ ID NO: 20 (human APOBEC-3H), SEQ ID NO: 21 (human APOBEC-3D), SEQ ID NO: 22 (human APOBEC-1), SEQ ID NO: 23 (mouse APOBEC-1), and SEQ ID NO: 24 (rat APOBEC-1).
27. The method of claim 1 , wherein the fusion protein comprises an amino acid sequence selected from the group consisting of: SEQ ID NO: 30 (Cas9:human AID fusion), SEQ ID NO: 31 (human AID:Cas9 fusion), SEQ ID NO: 32 (Cas9:mouse AID fusion), SEQ ID NO: 33 (human APOBEC-3G:Cas9 fusion), SEQ ID NO: 34 (human APOBEC-1:Cas9 fusion), and SEQ ID NO: 92 (Cas9:APOBEC1 fusion).
28. The method of claim 1 , wherein the cytidine deaminase is linked to a C-terminus of the Cas9 variant.