Site-directed integration of transgenes in mammals
The present disclosure provides a method of making a mammal (e.g., a rodent, such as a mouse) by integrating an intact polynucleotide sequence into a specific genomic locus of the mammal to result in a transgenic mammal. A transgenic mammal made by the methods of the present disclosure would contain a known copy number (e.g., one) of the inserted polynucleotide sequence at a predetermined location. The method involves introducing a site-specific recombinase and a targeting construct, containing a first recombination site and the polynucleotide sequence of interest, into the mammalian cell. The genome of the cell contains a second recombination site and recombination between the first and second recombination sites is facilitated by the site-specific, uni-directional recombinase. The result of the recombination is site-specific integration of the polynucleotide sequence of interest in the genome of the mammal. This inserted sequence is then also transmitted to the progeny of the mammal.
1. A method of inserting a polynucleotide sequence into a genome of a murine cell, comprising:
introducing a circular nucleic acid into said murine cell,
wherein said circular nucleic acid comprises said polynucleotide sequence and a first unidirectional recombination site, and
wherein said genome of said murine cell comprises a second unidirectional recombination site at the intergenic Hipp11 (H11) locus on mouse chromosome 11;
introducing an mRNA a nucleic acid encoding a site-specific, unidirectional recombinase into said cell; and
maintaining said cell under conditions that facilitate recombination between said first and second unidirectional recombination sites mediated by said unidirectional recombinase, wherein said method results in a site-specific integration of said polynucleotide sequence into the genome of said murine cell.
2. The method of claim 1 , wherein:
the circular nucleic acid comprises the polynucleotide sequence flanked by a first and a second copy of the first unidirectional recombination site; and
wherein the genome of the murine cell comprises a first and a second copy of the second unidirectional recombination site; and
wherein the method further comprises maintaining the cell under conditions that facilitate recombination between the first copies of the first and second unidirectional recombination sites and the second copies of the first and second unidirectional recombination sites, mediated by the unidirectional recombinase, wherein the method results in a site-specific integration of the polynucleotide sequence into the genome of the murine cell.
3. The method of claim 1 , wherein said murine cell is a zygote.
4. The method of claim 3 , wherein said zygote grows into a mammal containing said site-specific integration in both somatic cells and germline cells.
5. The method of claim 1 , wherein said unidirectional recombinase is φC31, TP901-1, or R4.
6. The method of claim 5 , wherein said first and second unidirectional recombination sites are selected from wild-type attB, wild-type attP, pseudo-sites thereof, or tandem repeats thereof.
7. The method of claim 6 , wherein said pseudo-attB or pseudo-attP is derived from a sequence native to a murine genome.
8. The method of claim 1 , wherein said nucleic acid encoding said site-specific, unidirectional recombinase is introduced into the cell before or concurrent to said introducing a circular nucleic acid.
9. The method of claim 1 , wherein the murine cell lacks a promoter sequence at or near the second unidirectional recombination site.
10. The method of claim 1 , wherein the circular nucleic acid lacks a bacterial plasmid sequence.
11. The method of claim 1 , wherein the polynucleotide sequence encodes a polypeptide product.
12. The method of claim 1 , wherein the nucleic acid encoding the site-specific, unidirectional recombinase is an mRNA.
13. The method of claim 12 , wherein first unidirectional recombination site comprises wild-type attB or tandem repeats thereof and the second unidirectional recombination site comprises wild-type attP or tandem repeats thereof and wherein the unidirectional recombinase is φC31.
14. The method of claim 13 , wherein said murine cell is a zygote and the introducing said circular nucleic acid and said nucleic acid encoding the site-specific, unidirectional recombinase comprises injecting said circular nucleic acid and said nucleic acid encoding the site-specific, unidirectional recombinase into pronucleus of the zygote.
15. The method of claim 1 , wherein the nucleic acid encoding the site-specific, unidirectional recombinase is a circular DNA.
16. The method of claim 1 , wherein said murine cell is a zygote and the introducing said circular nucleic acid and said nucleic acid encoding the site-specific, unidirectional recombinase comprises injecting said circular nucleic acid and said nucleic acid encoding the site-specific, unidirectional recombinase into pronucleus of the zygote.