Methods for detecting nucleic acid variants
Methods for detecting a short genetic variant in a test sample are described herein. In some exemplary methods, the short genetic variant is called using one or match scores, which are determined using one or more sequencing data sets obtained from a test nucleic acid molecule, wherein the test sequencing data sets are determined by sequencing the test nucleic acid molecule using non-terminating nucleotides provided in separate nucleotide flows according to a flow-cycle order. Also described herein are methods of sequencing a test nucleic acid molecule using two or more different flow-cycle orders and/or extended flow cycle orders having five or more nucleotide flows per flow cycle.
1 . A method for sequencing, comprising:
obtaining a first test sequencing data set associated with a first test nucleic acid molecule comprising a short genetic variant, wherein the first test sequencing data set was determined by sequencing the first test nucleic acid molecule using non-terminating nucleotides provided in separate nucleotide flows according to a first flow-cycle order, and wherein the first test sequencing data set comprises flow signals at flow positions corresponding to the nucleotide flows, wherein the first test sequencing data set differs from a first reference sequencing data set at four or more consecutive flow positions, wherein the first reference sequencing data set is associated with a first reference sequence that corresponds to the first test nucleic acid molecule and does not have the short genetic variant, and is determined based on the first flow-cycle order;
obtaining a second test sequencing data set associated with a second test nucleic acid molecule comprising the short genetic variant, wherein the second test sequencing data set was determined by sequencing the second test nucleic acid molecule using non-terminating nucleotides provided in separate nucleotide flows according to a second flow-cycle order, wherein the first flow-cycle order and the second flow-cycle order are different, and wherein the test sequencing data set comprises flow signals at flow positions corresponding to the nucleotide flows, wherein the second test sequencing data set does not differ from a second reference sequencing data set at four or more consecutive flow positions, wherein the second reference sequencing data set is associated with a second reference sequence that corresponds to the second test nucleic acid molecule and does not have the short genetic variant, and is determined based on the second flow-cycle order; and
detecting the short genetic variant in a sample nucleic acid molecule by subjecting the sample nucleic acid molecule to the first flow-cycle order out of a plurality of different flow-cycle orders.
2 . The method of claim 1 , further comprising sequencing the first test nucleic acid molecule using non-terminating nucleotides provided in separate nucleotide flows according to the first flow-cycle order to obtain the first test sequencing data set, and sequencing the second test nucleic acid molecule using non-terminating nucleotides provided in separate nucleotide flows according to the second flow-cycle order to obtain the second test sequencing data set.
3 . The method of claim 1 , further comprising:
determining, for the first sequencing data set and second sequencing data set, a match score to one or more candidate sequences, wherein the match score is indicative of a likelihood that the first test sequencing data set, the second test sequencing data set, or both, matches a candidate sequence from one or more candidate sequences; and
calling, using the determined match scores, the presence or absence of a short genetic variant in the test sample.
4 . The method of claim 3 , further comprising:
selecting a target short genetic variant, wherein a target sequencing data set associated with a target sequence comprising the target short genetic variant differs from a reference sequencing data set associated with a reference sequence at two or more flow positions when the target sequencing data set and the reference sequencing data set are obtained by sequencing the target sequence using non-terminating nucleotides provided in separate nucleotide flows according to the first flow-cycle order or the second flow-cycle order, wherein the one or more candidate sequences comprises the target sequence and the reference sequence.
5 . The method of claim 4 , wherein the target short genetic variant is selected prior to calling the presence or absence of the target short genetic variant in the test sample.
6 . The method of claim 4 , comprising generating a personalized biomarker panel for a subject associated with the test sample, the biomarker panel comprising the target short genetic variant present in the test sample.
7 . The method of claim 4 , wherein the reference sequencing data set is obtained by determining an expected reference sequencing data set where the reference sequence is sequenced using non-terminating nucleotides provided in separate flows according to the first flow-cycle order or the second flow-cycle order.
8 . The method of claim 4 , wherein the target sequence differs from the reference sequence at two or more flow positions according to both the first flow-cycle order and the second flow-cycle order.
9 . The method of claim 4 , wherein the target sequence differs from the reference sequence across one or more flow-cycles according to the first flow-cycle order or the second flow-cycle order.
10 . The method of claim 3 , wherein at least one of the one or more candidate sequences is a variant sequence.
11 . The method of claim 3 , wherein at least one of the one or more candidate sequences is a haplotype sequence.
12 . The method of claim 3 , wherein the short genetic variant comprises a single nucleotide polymorphism or an indel.
13 . The method of claim 3 , wherein the match score is indicative of a likelihood that the first test sequencing data set matches the candidate sequence, or the likelihood that the second test sequencing data set matches the candidate sequence.
14 . The method of claim 3 , further comprising generating a report that indicates the presence, identity, or absence of the short genetic variant in the test sample.
15 . The method of claim 14 , further comprising providing the report to a patient or a healthcare representative of the patient.
16 . The method of claim 3 , wherein the one or more candidate sequences comprises two or more different candidate sequences, the method further comprises:
selecting a candidate sequence from the two or more different candidate sequences, wherein the selected candidate sequence has the highest likelihood match with the first test sequencing data set, the second test sequencing data set, or both; and
calling, using the selected candidate sequence, the presence or absence of the short genetic variant in the test sample.
17 . The method of claim 16 , wherein at least one non-selected candidate sequence from the two or more different candidate sequences differs from the selected candidate sequence at two or more flow positions according to the first flow-cycle order or the second flow-cycle order.
18 . The method of claim 1 , wherein the flow signals comprise a base count indicative of a number of bases of the test nucleic acid molecule sequenced at each flow position.
19 . The method of claim 1 , wherein the flow signals comprise a statistical parameter indicative of a likelihood for at least one base count at each flow position, wherein the base count is indicative of a number of bases of the test nucleic acid molecule sequenced at the flow position.
20 . The method of claim 1 , wherein the flow signals comprise a statistical parameter indicative of a likelihood for a plurality of base counts at each flow position, wherein each base count is indicative of a number of bases of the test nucleic acid molecule sequenced at the flow position.
21 . The method of claim 1 , wherein the first flow-cycle order or the second flow-cycle order comprises 4 separate flows repeated in the same order.
22 . The method of claim 1 , wherein the first flow-cycle order or the second flow-cycle order comprises 5 or more separate flows repeated in the same order.
23 . The method of claim 1 , further comprising:
providing a test nucleic acid molecule;
providing non-terminating nucleotides in separate nucleotide flows according to a first flow-cycle order, extending a sequencing primer along the test nucleic acid molecule, and detecting the presence or absence of nucleotide incorporation into the sequencing primer after each nucleotide flow to generate the first test sequencing data set;
removing the extended sequencing primer; and
providing the non-terminating nucleotides in separate nucleotide flows according to the second flow-cycle order, extending a sequencing primer along the test nucleic acid molecule, and detecting the presence or absence of nucleotide incorporation into the sequencing primer after each nucleotide flow to generate the second test sequencing data set.
24 . The method of claim 23 , wherein the separate flows comprise a single base type.
25 . The method of claim 23 , wherein at least one of the separate flows comprise 2 or 3 different base types.
26 . The method of claim 23 , further comprising sequencing a plurality of test nucleic acid molecules using non-terminating nucleotides provided in separate nucleotide flows according to the first flow-cycle order to obtain a plurality of first test sequencing data sets, and sequencing the plurality of test nucleic acid molecule using non-terminating nucleotides provided in separate nucleotide flows according to the second flow-cycle order to obtain a plurality of second test sequencing data sets.
27 . The method of claim 1 , further comprising selecting the first flow-cycle order from the plurality of different flow-cycle orders based on the first test sequencing data set differing from the first reference sequencing data set at four or more consecutive flow positions.