Methods, systems and processes of identifying genetic variation in highly similar genes
Provided herein are novel methods, systems and processes for mapping sequence reads to a modified reference genome and determining the presence or absence of a genetic variation, or the likelihood thereof, in a gene of interest in a subject.
1. A computer-implemented method for determining a likelihood of a presence or absence of a genetic variation in a gene of interest for a subject, the method comprising:
(a) providing a reference genome comprising (i) the gene of interest and (ii) a counterpart gene to the gene of interest, wherein at least one exon of the counterpart gene and the gene of interest are 70% to 99% identical;
(b) substituting at least 30% of nucleotides in the at least one exon of the counterpart gene of the reference genome with an ambiguous nucleotide marker, thereby providing a modified reference genome;
(c) mapping sequence reads obtained from a diploid subject to the modified reference genome, wherein (i) the subject comprises the gene of interest and the at least one exon of the counterpart gene, (ii) the sequence reads are obtained using a massively parallel sequencing method, and (iii) the sequence reads derived from the at least one exon of the counterpart gene of the subject map to the at least one exon of the gene of interest of the modified reference genome and not to the at least one exon of the counterpart gene of the modified reference genome; and
(d) determining the likelihood of a presence or absence of a genetic variation in the gene of interest for the subject according to the sequence reads mapped to the modified reference genome.
2. The method of claim 1 , wherein the mapping of (c) comprises an expectation that at least 4 alleles of the at least one exon of the gene of interest for the subject map to the gene of interest of the modified reference genome.
3. The method of claim 1 , wherein a ploidy of at least 4 is expected for the gene of interest for the subject.
4. The method of claim 1 , wherein the at least one exon of the counterpart gene and the gene of interest in the reference genome are 80% to 99% identical, prior to substituting of step (b).
5. The method of claim 1 , wherein the gene of interest for the subject comprises a genetic variation not present in the gene of interest in the reference genome.
6. The method of claim 1 , wherein the counterpart gene to the gene of interest is a pseudogene.
7. The method of claim 1 , wherein the substituting of step (b) comprises substituting at least 90% of the nucleotides in the at least one exon of the counterpart gene of the reference genome with an ambiguous nucleotide marker.
8. The method of claim 1 , wherein the gene of interest and the at least one exon of the counterpart gene of the subject comprise two alleles.
9. The method of claim 1 , wherein the sequence reads are obtained for an entire genome.
10. The method of claim 1 , wherein the sequence reads are obtained by a method comprising paired-end sequencing.
11. The method of claim 1 , wherein the gene of interest of the subject is selected from GBA, NEB, SMN1, IKBKG, PMS2, HBA1, HBG1, HBB, SBSD, and VWF.
12. The method of claim 1 , wherein the gene of interest of the reference genome is PMS2 and the counterpart gene of the reference genome is PMS2CL.
13. The method of claim 1 , wherein the gene of interest of the reference genome is HBA1 and the counterpart gene of the reference genome is HBA2.
14. The method of claim 1 , wherein the gene of interest of the reference genome is HBG1 and the gene of interest of the reference genome is HBG2.
15. The method of claim 1 , wherein the gene of interest of the reference genome is HBB and the gene of interest of the reference genome is HBD.
16. The method of claim 1 , wherein the gene of interest of the reference genome is SBDS and the gene of interest of the reference genome is SBDSP1.
17. The method of claim 1 , wherein the gene of interest of the reference genome is CYP2D6, CYP21A2, CYP11B1, CYP11B2, PKD1 or PRSS1.
18. The method of claim 1 , where the determining of (d) comprises determining the presence or absence of the genetic variation in the gene of interest for the subject.
19. The method of claim 1 , wherein the ambiguous nucleotide marker is an N.
20. A computer-implemented method for determining a likelihood of a presence or absence of a genetic variation in a gene of interest for a subject the method comprising:
(a) providing a reference genome comprising (i) the gene of interest and (ii) a counterpart gene to the gene of interest, wherein the gene of interest is selected from the group consisting of PMS2, HBA1, HBG1, HBB, and SBSD and the counterpart gene to the gene of interest is selected from PMS2CL, HBA2, HBG2, HBD and SBDSP1, respectively;
(b) substituting at least 30% of nucleotides in at least one exon of the counterpart gene of the reference genome with an ambiguous nucleotide marker, thereby providing a modified reference genome;
(c) mapping sequence reads obtained from a diploid subject to the modified reference genome, wherein (i) the subject comprises the gene of interest and the at least one exon of the counterpart gene, (ii) the sequence reads are obtained using a massively parallel sequencing method, and (iii) the sequence reads derived from the at least one exon of the counterpart gene of the subject map to the at least one exon of the gene of interest of the modified reference genome and not to the at least one exon of the counterpart gene of the modified reference genome; and
(d) determining the likelihood of the presence or absence of a genetic variation in the gene of interest for the subject according to the sequence reads mapped to the modified reference genome.