Simultaneous, sequencing-based analysis of proteins, nucleosomes, and cell-free nucleic acids from a single biological sample
The invention provides a method for the analysis of a biological sample to determine multiple types of information therefrom in a streamlined, combined workflow, where all information is obtained in a sequencing-based analysis. The information includes the presence and concentration of specific plasma proteins in a blood sample: the number, location, and types of histone modifications associated with cell-free DNA obtained from the same sample: the sequence of cfRNA and cfDNA in the cell-free DNA sample; and epigenetic information pertaining to the cell-free DNA, such as hydroxy methylation and methylation profiles, i.e., the distribution of 5-hydroxymethylcytosine (5hmC) and 5-methylcy tosine (5mC) residues, respectively. The invention additionally pertains to a classical sequencing-based method for analyzing a biological sample to determine one or more non-classical sequence features of the sample. Compositions, kits, and related methods are also provided, including an embodiment in which truncated sequencing adapters are used in conjunction with barcoded PCR primers.
1 . A method for preparing a cell-free nucleic acid sample to enable identification of at least one histone modification in a nucleosome contained therein using a DNA sequencing-based technique, the method comprising:
(a) providing a cell-free nucleic acid sample containing a plurality of nucleosomes each comprising a cfDNA molecule wound around a histone core;
(b) ligating adapters comprising terminal hybridizing regions to the ends of the cfDNA molecules, thereby providing a modified cell-free nucleic acid sample comprising adapter-ligated cfDNA molecules each wound around a histone core;
(c) providing a proximity probe comprising, at a first terminus, a histone modification binding domain that specifically binds to a histone modification of interest; at a second terminus, a nucleic acid binding domain complementary to a terminal hybridizing region; and a non-hybridizing region therebetween comprising a nucleic acid sequence that corresponds to the histone modification of interest and thereby serves as a histone modification barcode, wherein the proximity probe is dimensioned to allow for simultaneous binding of the histone modification binding domain to the histone modification of interest and hybridization of the the nucleic acid binding domain complementary to the terminal hybridizing region;
(d) incubating the modified cell-free nucleic acid sample with the proximity probe under conditions effective to facilitate (i) binding of the histone modification binding domain to the histone modification and (ii) hybridization of the complementary nucleic acid binding domain with the terminal hybridizing region to form a dsDNA segment with a 5′ terminus originating with the cell-free DNA and a 3′ terminus originating with the proximity probe and comprising the histone modification barcode; and
(e) extending the 5′ terminus of the dsDNA segment along the non-hybridizing region of the proximity probe and the histone modification barcode by adding a polymerase and a mixture of dNTPs, thereby providing a histone modification-barcoded dsDNA template molecule for amplification and sequencing.
2 . The method of claim 1 , wherein step (c) comprises providing a plurality of proximity probes each targeting a different histone modification.
3 . The method of claim 2 , further comprising amplifying the histone modification-barcoded dsDNA template molecules.
4 . The method of claim 3 , further comprising sequencing the amplified, histone modification-barcoded dsDNA template molecules and determining information about the type and location of histone modifications from the histone modification barcodes observed in the sequence reads generated.
5 . A combined workflow process for extracting multiple types of data from a cell-free nucleic acid sample, comprising:
(a) ligating an adapter comprising a hybridizing nucleic acid region to each terminus of nucleosome-associated DNA in a single, cell-free nucleic acid sample, thereby providing a modified cell-free nucleic acid sample comprising nucleosomes associated with adapter-ligated DNA;
(b) providing a proximity probe comprising a histone modification binding domain at a first terminus, a nucleic acid binding domain complementary to the hybridizing nucleic acid region at an opposing second terminus, and a non-hybridizing region therebetween comprising a nucleic acid sequence selected to correspond to a specific histone modification and thereby serve as a histone modification barcode, wherein the proximity probe is dimensioned to allow for simultaneous binding of the histone modification binding domain to the histone modification and the hybridization of the complementary nucleic acid binding domain with the hybridizing nucleic acid region;
(c) incubating the modified cell-free nucleic acid sample with the proximity probe under conditions effective to facilitate (i) binding of the histone modification binding domain to the histone modification and (ii) hybridization of the complementary nucleic acid binding domain with the hybridizing nucleic acid region to form a dsDNA segment with a 5′ terminus originating with the cell-free DNA and a 3′ terminus originating with the proximity probe; and
(d) extending the 5′ terminus of the segment along the non-hybridizing region of the proximity probe and the histone modification barcode by adding a polymerase and a mixture of dNTPs, thereby providing a histone modification-barcoded dsDNA template molecule for further processing and sequencing;
(e) purifying nucleic acids in the sample to provide a purified nucleic acid composition comprising histone modification-barcoded dsDNA and DNA;
(f) functionalizing 5hmC residues in the purified nucleic acid composition with a first affinity tag that allows selective removal of 5hmC-containing species, thereby providing tagged 5hmC-containing DNA;
(g) removing the tagged 5hmC-containing DNA from the purified nucleic acid composition, with untagged DNA remaining, wherein the untagged DNA comprises the histone modification-barcoded dsDNA template molecule; and
(h) appending a 5hmC process barcode to the tagged 5hmC-containing DNA, thereby providing a process-barcoded, tagged 5hmC-containing template molecule.
6 . The process of claim 5 , further comprising:
(i) amplifying and sequencing the histone modification-barcoded dsDNA template molecule and the process-barcoded, tagged 5hmC-containing DNA template molecule.
7 . The process of claim 6 , wherein the histone modification-barcoded dsDNA template molecule and the process-barcoded, 5hmC-containing DNA template molecule are pooled prior to amplification and sequencing.
8 . The process of claim 6 , wherein following step (d), adapters comprising an additional barcode are ligated to the histone modification-barcoded dsDNA.
9 . The process of claim 8 , wherein the additional barcode comprises a source identifier sequence.
10 . The process of claim 9 , wherein the additional barcode further comprises a fragment identifier sequence, a strand identifier sequence, or both a fragment identifier sequence and a strand identifier sequence.
11 . The process of claim 5 , wherein the cell-free nucleic acid sample is obtained from a blood sample.
12 . The process of claim 11 , further comprising carrying out a plasma protein analysis on a fraction of the blood sample.
13 . The process of claim 12 , wherein plasma proteins are analyzed by generating a dsDNA template molecule comprising a protein identifier barcode corresponding to a protein analyte.
14 . The process of claim 13 , further comprising amplifying and sequencing the histone modification-barcoded dsDNA template molecule, the process-barcoded, 5hmC-containing DNA template molecule, and the protein-barcoded dsDNA template molecule.
15 . The process of claim 14 , wherein the histone modification-barcoded dsDNA template molecule, the process-barcoded, 5hmC-containing DNA template molecule, and the protein-barcoded dsDNA template molecule are pooled prior to amplification and sequencing.
16 . The method of claim 5 , further including:
synthesizing a first strand of cDNA from RNA in the cell-free nucleic acid sample;
synthesizing a second strand of cDNA complementary to the first strand to provide a cDNA duplex; and
covalently attaching to at least one terminus of the cDNA duplex, in the absence of a ligase, a cDNA adapter comprising a sequence that includes a source identifier barcode and an RNA indicator barcode, thereby providing a nucleic acid composition comprising adapter-bound cDNA and the histone modification-barcoded dsDNA template molecule.
17 . The process of claim 16 , further comprising:
amplifying and sequencing the histone modification-barcoded dsDNA template molecule, the adapter-bound cDNA, and the process-barcoded, tagged 5hmC-containing DNA template molecule.
18 . The process of claim 17 , wherein the histone modification-barcoded dsDNA template molecule, the process-barcoded, 5hmC-containing DNA template molecule, and the adapter-bound cDNA are pooled prior to amplification and sequencing.