Methods and computer software for detecting splice variants
View Patent ↗Methods and software products for analysis of alternative splicing are disclosed. In general the methods involve normalizing probe set or exon intensity to an expression level measurement of the gene. The methods may be used to identify tissue-specific alternative splicing events.
1. A computer-implemented method for identifying exons of a gene that are differentially expressed within at least three samples, the method comprising:
providing a computer, wherein the computer comprises a computer program;
obtaining a gene signal for a gene in each sample;
obtaining an exon signal for exons of the gene in each sample;
calculating, with the computer program, an expected exon signal for an exon of the gene;
correlating, with the computer program, the exon signal with the expected exon signal; and
identifying the exon as differentially expressed based upon, at least in part, a low correlation between the exon signal and the expected exon signal.
2. The method of claim 1 , wherein the calculation for an expected exon signal is based upon an assumption that, in the absence of differential expression of exons within the gene, an exon of the gene is expressed proportionately to the expression of the gene.
3. The method of claim 2 , wherein the calculation for expected exon signals is based upon, at least in part, the formula:
e i,j,k =(α i,k )( g j,k ),
wherein e i,j,k is the expected exon signal of the i-th exon of the k-th gene in the j-th sample, wherein α i,k is the ratio of the i-th exon signal to the k-th gene signal over all samples, and wherein g j,k is the gene signal of the k-th gene in the j-th sample.
4. The method of claim 1 , wherein the low correlation for an exon differently expressed within the samples is a negative value.
5. The method of claim 1 , wherein the obtained gene signal is based upon all exons in the gene.
6. A computer-implemented method for identifying exons of a gene that are differentially expressed within a plurality of samples, the method comprising:
providing a computer, wherein the computer comprises a computer program;
obtaining a gene signal for a gene in each sample;
obtaining an exon signal for exons of the gene in each sample;
calculating, with the computer program, a ratio of the exon signal to the gene signal for an exon in each sample;
analyzing, with the computer program, the calculated ratios for the exon among the plurality of samples, wherein the analysis determines if the variance in the calculated ratios is statistically significant; and
identifying the exon as differentially expressed if the variance is statistically significant.
7. The method of claim 6 , wherein the calculated ratios for the exon is based upon, at least in part, the formula:
log( e i,j,k /g j,k ),
wherein e i,j,k is the exon signal of the i-th exon of the k-th gene in the j-th sample, and wherein g j,k is the gene signal of the k-th gene in the j-th sample.
8. The method of claim 6 , wherein the gene signal is based upon all exons of the gene.
9. The method of claim 8 , wherein the gene signal is based upon all probe sets for all exons of the gene.
10. The method of claim 6 , wherein the exon signal is based upon all probe sets for the exon.
11. The method of claim 6 , wherein a constant value is added to the gene signal and the exon signal before the ratio is calculated.
12. The method of claim 11 , wherein the constant value is based upon a percentile of a background signal.
13. The method of claim 12 , wherein the constant value is based upon approximately a twentieth percentile of the background signal.