MOSAIC TAGS FOR LABELING TEMPLATES IN LARGE-SCALE AMPLIFICATIONS
The invention relates to methods of labeling nucleic acids, such as fragments of genomic DNA, with unique sequence it referred to herein as “mosaic tag,” prior to amplification and/or sequencing. Such sequence tags are useful for identifying amplification and sequencing errors. Mosaic tags minimize sequencing and amplification artifacts due to inappropriate annealing priming, hairpin formation, or the like, that may occur with completely random sequence tags of the prior art. In one aspect, mosaic tags are sequence tags that comprise alternating constant regions and variable regions, wherein each constant region has it position in the mosaic tag and comprises a predetermined sequence of nucleotides and each variable region has a position in the mosaic tag and comprises a predetermined number of randomly selected nucleotides.
1 . A method for sequencing nucleic acids comprising:
preparing DNA templates front nucleic acids in a sample;
labeling by sampling the DNA templates to form a multiplicity tag-template conjugates, wherein substantially every DNA template of a tag-template conjugate has a unique mosaic tag comprising alternating constant regions and variable regions, each constant region having a position in the mosaic tag and a length of from 1 to 10 nucleotides of a predetermined sequence and each variable region having a position in the mosaic tag and a length of from 1 to 10 randomly selected nucleotides, such that constant regions having the same positions have the same lengths and variable region having the same positions have the same lengths;
amplifying the multiplicity of tag-template conjugates;
generating a plurality of sequence reads for each of the amplified tag-template conjugates; and
determining a nucleotide sequence of each of the nucleic acids by determining a consensus nucleotide at each nucleotide position of each plurality of sequence reads having identical mosaic tags.
2 . The method of claim 1 wherein said mosaic tag has a length in the range of from 10 to 100 nucleotides.
3 . The method of claim 2 wherein said mosaic tag comprises at least 8 nucleotide positions with randomly selected nucleotides.
4 . The method of claim 1 wherein said sample is from a species and wherein said predetermined sequences of said constant regions of said mosaic tag are selected so that nonspecific hybridization by said predetermined sequences to genomic sequences of the species or products thereof is minimized.
5 . The method of claim 4 wherein said sample is from a human.
6 . A method of determining clonotypes of an immune repertoire, the method comprising the steps:
(a) obtaining a sample from an individual comprising T-cells and/or B-cells;
(b) attaching mosaic tags to molecules of recombined nucleid acids of T-cell receptor genes or immunoglobulin genes of the T-cells and/or B-cells to form tag-molecule conjugates, wherein substantially every molecule of the tag-molecule conjugates has a unique mosaic tag;
(c) amplifying the tag-molecule conjugates;
(d) sequencing the tag-molecule conjugates; and
(e) aligning sequence reads of like mosaic tags to determine sequence reads corresponding to the same clonotypes types the repertoire.
7 . The method of claim 6 wherein said step of aligning further includes determining a nucleotide sequence of each of said clonotypes of each of said tag-molecule conjugate by determining a majority nucleotide at each nucleotide position of said clonotypes of said like mosaic tags.
8 . The method of claim 6 wherein said step of attaching includes labeling by sampling said molecules of recombined nucleic acids.
9 . A method of determining clonotypes of an immune repertoire, the method comprising the steps:
(a) obtaining a sample from an individual comprising T-cells and/or B-cells;
(b) labeling by sampling molecules from the T-cells and/or B-cells to form tag-molecule conjugates, wherein each tag of said conjugates has a sequence of the form:
[(N 1 N 2 . . . N Kj )(b 1 b 2 . . . b Lj )]M
wherein each N i , for i=1, 2, . . . , K j , is a nucleotide randomly selected from the group consisting of A, C, G and T; K i is an integer in the range of from 1 to 10 for each j less than or equal to M; each b i , for i= 1, 2, . . . L j , is a nucleotide; L j is an integer in the range of from 1 to 10 for each j less than or equal to M; such that every sequence tag (i) has the same Kj for every j and (ii) has the same sequences b 1 b 2 . . . b Lj for every j; and M is an integer greater than or equal to 2; and each molecule of said conjugates comprises a recombined nucleic acid from a T-cell receptor gene or an immunoglobulin gene;
(c) sequencing the tag-molecule conjugates; and
(d) aligning sequence reads of like tags to determine like clonotypes.
10 . The method of claim 9 wherein said step of aligning further includes determining a nucleotide sequence of each of said clonotype of each of said tag-molecule conjugate by determining a majority nucleotide at each nucleotide position of said clonotypes of said like tags.
11 . The method of claim 10 wherein said step of attaching is implemented in a reaction mixture such that said tags are present in the reaction mixture in a concentration at least 100 time that of said molecules of recombined nucleic acid.