Methods and compositions for improved probe specificity
The present disclosure relates in some aspects to methods and compositions for analysis of a target nucleic acid, such as in situ detection of a region of interest in a polynucleotide in a tissue sample. In some aspects, provided herein are methods and compositions for detecting a region of interest in a target nucleic acid. In some aspects, provided herein are circularizable probes and oligonucleotide probes for analyzing a target nucleic acid, in which corresponding hybridization regions between the circularizable probe and the oligonucleotide probe comprise a barcode region comprising one or more barcodes. In some aspects, the oligonucleotide probe and/or the circularizable probe comprise one or more modifications.
1 . A method for analyzing a biological sample, the method comprising:
a) contacting the biological sample comprising a target nucleic acid comprising hybridization region HR1′ and hybridization region HR2′, with:
(i) a circularizable probe comprising hybridization region HR1 and hybridization region HRb, wherein HR1 hybridizes to HR1′, and wherein HRb comprises a barcode region, and
(ii) an oligonucleotide probe comprising hybridization region HR2 and hybridization region HRb′, wherein HR2 hybridizes to HR2′ and wherein HRb′ hybridizes to HRb, and the oligonucleotide probe comprises one or more modifications;
b) ligating the ends of the circularizable probe using the oligonucleotide probe as a splint to generate a circularized probe;
c) using the oligonucleotide probe or a primer to prime rolling circle amplification (RCA) of the circularized probe to generate an RCA product; and
d) detecting the RCA product, thereby detecting the target nucleic acid in the biological sample.
2 . The method of claim 1 , wherein the circularizable probe further comprises hybridization region HRa, and the oligonucleotide probe further comprises hybridization region HRa′ which hybridizes to HRa.
3 . The method of claim 1 , wherein:
HRb′ comprises a barcode region complementary to the barcode region of HRb,
in step a), the biological sample is contacted with another oligonucleotide probe comprising hybridization region HRb″, wherein HRb″ comprises a barcode region that is not complementary to the barcode region of HRb, and
in step c), HRb″ or a portion thereof is not configured to prime RCA of a circularized probe generated by ligation using the another oligonucleotide probe as a splint.
4 . The method of claim 1 , wherein the one or more modifications protect the oligonucleotide probe from 3′→5′ exonuclease degradation, and wherein:
(i) the one or more modifications allow primer extension by a polymerase, and the method does not comprise contacting the biological sample with an enzyme capable of removing the one or more modifications; or
(ii) the one or more modifications block primer extension by a polymerase, and the method further comprises contacting the biological sample with an agent capable of removing the one or more modifications.
5 . The method of claim 1 , wherein the one or more modifications comprise a terminal modification.
6 . The method of claim 1 , wherein the biological sample is contacted with another oligonucleotide probe comprising HRa′ and hybridization region HRb″ in the 5′ to 3′ direction, wherein HRb″ comprises (i) a region complementary to a non-barcode region of HRb and (ii) a barcode region that is not complementary to the barcode region of HRb.
7 . The method of claim 1 , wherein HRb′ comprises one or more uracil-containing residues and/or nuclease cleavage sites cleavable by an enzyme or a uracil-specific excision reagent.
8 . The method of claim 6 , wherein:
the barcode region in HRb″ remains single-stranded and is cleaved by the enzyme, and/or
the barcode region of HRb remains single-stranded and is cleaved by the enzyme.
9 . The method of claim 6 , wherein the barcode region in HRb″ corresponds to another target nucleic acid distinct from the target nucleic acid.
10 . A method for analyzing a biological sample, the method comprising:
a) contacting the biological sample comprising a target nucleic acid comprising in the 5′ to 3′ direction: hybridization region HR1′ and hybridization region HR2′, with:
(i) a plurality of circularizable probes, wherein a circularizable probe of the plurality of circularizable probes comprises hybridization region HRa, hybridization region HR1, and hybridization region HRb, wherein HRb comprises a barcode region, and
(ii) a plurality of oligonucleotide probes, wherein an oligonucleotide probe of the plurality of oligonucleotide probes comprises hybridization region HR2, hybridization region HRa′, and hybridization region HRb′, wherein HRb′ or a portion thereof is complementary to the barcode region of HRb; and wherein:
HRa hybridizes to HRa′, HR1 hybridizes to HR1′, and HR2 hybridizes to HR2′;
b) ligating HRa and HRb using the oligonucleotide probe as a splint, wherein the circularizable probe is circularized to generate a circularized probe;
c) using the oligonucleotide probe or a portion thereof or a primer to prime rolling circle amplification (RCA) of the circularized probe to generate an RCA product; and
d) detecting the RCA product, thereby detecting the target nucleic acid in the biological sample.
11 . The method of claim 10 , wherein:
the circularizable probe comprises HRa, HR1, and HRb in the 5′ to 3′ direction,
the oligonucleotide probe comprises HR2, HRa′, and HRb′ in the 5′ to 3′ direction, and
the target nucleic acid comprises HR1′ and HR2′ in the 5′ to 3′ direction.
12 . The method of claim 1 , wherein the barcode region is at the 3′ end of the circularizable probe.
13 . The method of claim 11 , wherein:
the plurality of oligonucleotide probes comprises another oligonucleotide probe comprising HRa′ and hybridization region HRb″, wherein HRb″ comprises (i) a region complementary to a non-barcode region of HRb and (ii) a barcode region that is not complementary to the barcode region of HRb; and
the barcode region in HRb″ is not hybridized to the barcode region of HRb.
14 . The method of claim 10 , wherein the circularizable probe comprises a sequence 5′ to HRa, and the sequence 5′ to HRa forms a 5′ flap that does not hybridize to the oligonucleotide probe.
15 . The method of claim 14 , comprising cleaving the 5′ flap of the circularizable probe using an enzyme.
16 . A method, comprising:
a) contacting a biological sample comprising a target nucleic acid comprising in the 5′ to 3′ direction: hybridization region HR1′ and hybridization region HR2′, with:
(i) a plurality of circularizable probes, wherein a circularizable probe of the plurality of circularizable probes comprises, in the 5′ to 3′ direction: a 5′ flap, hybridization region HRa, hybridization region HR1, and hybridization region HRb, wherein HRb comprises a barcode region, and
(ii) a plurality of oligonucleotide probes, wherein an oligonucleotide probe of the plurality of oligonucleotide probes comprises in the 5′ to 3′ direction: hybridization region HR2, hybridization region HRa′, and hybridization region HRb′, wherein HRb′ or a portion thereof is complementary to the barcode region of HRb; and wherein:
HRa hybridizes to HRa′, HR1 hybridizes to HR1′, and HR2 hybridizes to HR2′;
b) cleaving the 5′ flap of the circularizable probe by an enzyme;
c) ligating HRa and HRb using the oligonucleotide probe as a splint, wherein the circularizable probe is circularized to generate a circularized probe;
d) using the oligonucleotide probe or a portion thereof to prime rolling circle amplification (RCA) of the circularized probe to generate an RCA product; and
e) detecting the RCA product, thereby detecting the target nucleic acid in the biological sample.
17 . The method of claim 16 , wherein the enzyme is a flap endonuclease 1 (FEN1) and a Thermus thermophilus (Tth) polymerase is used in d) to generate the RCA product.
18 . The method of claim 10 , wherein:
the barcode region in HRb is a first barcode region and HRa comprises a second barcode region, wherein the first and second barcode regions each independently comprises one or more barcodes,
optionally wherein: (i) the first barcode region corresponds to the target nucleic acid or sequence thereof; (ii) the second barcode region corresponds to the target nucleic acid or sequence thereof; or (iii) the combination of the first and second barcode regions correspond to the target nucleic acid or sequence thereof.
19 . The method of claim 1 , wherein the RCA product is generated and detected in situ in the biological sample.
20 . The method of claim 10 , wherein the RCA product is generated and detected in situ in the biological sample.