System and computer software products for comparative gene expression analysis
View Patent ↗Methods and computer software products are provided for analyzing gene expression data. In one embodiment, methods, systems and computer software are provided for comparative gene expression analysis using intensity dependent normalization factors.
1. A computer implemented method for calculating a normalization factor comprising:
providing a first intensity value (I (1) ) of a probe in a first probe array and a second intensity value (I (2) ) of said probe in a second probe array, wherein the intensity values are referential intensity values that indicate nucleic acid hybridization;
obtaining the geometric mean (x) of said I (1) and said I (2) ;
calculating said normalization factor according to:
f(x)=e h(x) , wherein said h(x) is derived from the referential intensity values from said first and second probe arrays; and
using said normalization factor for gene expression analysis and outputting the result of said analysis.
2. The method of claim 1 wherein said h(x) is derived by relating geometric means (x i ′) of first referential intensities (RI i (1) ) in the first probe array and second referential intensities (RI i (2) ) in the second probe array to:
y
i
=
log
(
RI
i
(
1
)
RI
i
(
2
)
)
.
w
=
x
─
1
+
1
-
x
x
─
1
+
1
-
x
─
1
,
i
=
1
,
…
,
m
-
1
,
3. The method of claim 2 wherein said relating comprising:
sorting (x i , y i ) pairs according to x i into a plurality (m number) of bins with no overlapping;
computing medians ( x k ) of x i 's and medians ( y k ) of y i 's for each bin; and interpolating said medians ( x k , y k ).
4. The method of claim 3 wherein said bins are of approximately equal size.
5. The method of claim 4 wherein said h(x) is:
h
(
x
)
=
{
y
─
1
,
w
y
_
1
+
(
1
-
w
)
y
_
1
+
1
,
y
─
m
,
if
x
≤
x
_
1
if
x
∈
(
x
_
i
,
x
_
i
+
1
)
,
if
x
>
x
_
m
.
w
=
x
─
1
+
1
-
x
x
─
1
+
1
-
x
─
i
,
i
=
1
,
…
,
m
-
1
,
6. The method of claim 5 wherein said m is 3.
7. A system for calculating a normalization factor comprising:
a processor; and
a memory coupled with the processor, the memory storing a plurality of machine instructions that cause the processor to perform a plurality of logical steps when implemented by the processor, the logical steps comprising:
providing a first intensity value (I (1) ) of a probe in a first probe array and a second intensity value (I (2) ) of said probe in a second probe array, wherein the intensity values are referential intensity values that indicate nucleic acid hybridization;
obtaining the geometric mean (x) of said I (1) and said I (2) ;
calculating said normalization factor according to:
f(x) e h(x) , wherein said h(x) is derived from the referential intensity values from said first and second probe arrays; and
using said normalization factor for gene expression analysis and outputting the result of said analysis.
8. The system of claim 7 wherein said h(x) is derived by relating geometric means (xi′) of first referential intensities (R i (1) ) in the first probe array and second referential intensities (R i (2) ) in the second probe array to:
y
i
′
=
log
(
RI
i
(
1
)
RI
i
(
2
)
)
.
9. The system of claim 8 wherein said relating comprising:
sorting (x i , y i ) pairs according to x i into a plurality (m number) of bins with no overlapping;
computing medians ( x k ) of x i 's and medians ( y k ) of y i 's for each bin; and
interpolating said medians ( x k , y k ).
10. The system of claim 9 wherein said bins are of approximately equal size.
11. The system of claim 10 wherein said h(x) is:
h
(
x
)
=
{
y
─
1
,
w
y
_
i
+
(
1
-
w
)
y
_
i
+
1
,
y
─
m
,
if
x
≤
x
_
1
if
x
∈
(
x
_
i
,
x
_
i
+
1
]
,
if
x
>
x
_
m
.
w
=
x
─
i
+
1
-
x
x
─
i
+
1
+
-
x
─
i
,
i
=
1
,
…
,
m
-
1
,
12. The system of claim 11 wherein said m is 3.
13. A computer software product for calculating a normalization factor comprising:
computer program code for providing a first intensity value (I (1) ) of a probe in a first probe array and a second intensity value (I (2) ) of said probe in a second probe array, wherein the intensity values are referential intensity values that indicate nucleic acid hybridization;
computer program code for obtaining the geometric mean (x) of said I (1) and said I (2) ;
computer program code for calculating said normalization factor according to:
f(x)=e h(x) , wherein said h(x) is derived from the referential intensity values from said first and second probe arrays; and
computer program code for using said normalization factor for gene expression analysis and outputting the result of said analysis; and
a computer readable medium for storing said codes.
14. The computer software product of claim 13 wherein said h(x) is derived by relating geometric means (x i ′) of first referential intensities (RI i (1) ) in the first probe array and second referential intensities (RI i (2) ) in the second probe array to:
y
i
=
log
(
RI
i
(
1
)
RI
i
(
2
)
)
.
w
=
x
─
1
+
1
-
x
x
─
1
+
1
-
x
─
1
,
i
=
1
,
…
,
m
-
1
,
15. The computer software product of claim 14 wherein said code for relating comprising:
computer program code for sorting (x i , y i ) pairs according to x1 into a plurality (m number) of bins with no overlapping;
computer program code for computing medians ( x k ) of x i 's and medians ( y k ) of y i 's for each bin; and
computer program code for interpolating said medians ( x k , y k ).
16. The computer software product of claim 15 wherein said bins are of approximately equal size.
17. The computer software product of claim 16 wherein said h(x) is:
h
(
x
)
=
{
y
─
1
,
w
y
_
1
+
(
1
-
w
)
y
_
1
+
1
,
y
─
m
,
if
x
≤
x
_
1
if
x
∈
(
x
_
i
,
x
_
i
+
1
)
,
if
x
>
x
_
m
.
w
=
x
─
1
+
1
-
x
x
─
1
+
1
-
x
─
i
,
i
=
1
,
…
,
m
-
1
,
18. The computer software product of claim 17 wherein said m is 3.