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Data Set Group: NCI Mammary mRNA M430 (July04) modify this page

Data Set: NCI Mammary mRNA M430 (July04) RMA modify this page
GN Accession: GN37
GEO Series: No Geo series yet
Title:
Organism: Mouse (mm10)
Group: AKXD
Tissue: Mammary Tumors mRNA
Dataset Status: Public
Platforms: Affy Mouse Genome 430A, 430B, 430A 2.0 (GPL339,GPL340)
Normalization: RMA
Contact Information
Kent Hunter
U.S. National Institute of Health
Building 37, Room 5046C, 37 Convent Drive
Bethesda, MD 20892 USA
Tel. 301-435-8957
hunterk@mail.nih.gov
Website
Download datasets and supplementary data files

Specifics of this Data Set:
None

Summary:

Used the Affymetrix M430A and M430B pair of arrays (total of 45,137 probe sets). Data available as CEL files from GeneNetwork upon request.



About the cases used to generate this set of data:
The lines of mice used in this NCI-sponsored project consist of 18 groups of isogenic F1 progeny made by crossing females from each of 18 AKXD recombinant inbred strains (AKXD2, 3, 7, 9, 10, 11, 13, 14, 16, 18, 20, 21, 22, 23, 24, 25, 27, and 28) to male FVB/N mice that carry a transgene that consistently leads to the development of mammary tumors in females (e.g. Le Voyer et al., 2001). The formal nomenclature of the male transgenic line is FVB/N-TgN(MMTV-PyMT)634Mul. The genomes of each AKXD x FVB F1 consist of one set of FVB chromosomes (including the transgene) and one set of chromosomes inherited from one of the 18 AKXD RI strain mothers. Only the AKXD chromosomes are "recombinant" across this panel of F1 progeny, and the set therefore has a genetic architecture similar to backcross progeny. It is possible to map modifiers that influence tumor characteristics and expression patterns. It is also possible to study covariance of transcript expression levels in tumor tissue. For further background on this special mapping design please see Hunter and Williams (2002).
The ancestral strains from which all AKXD strains are derived are AKR/J (AKR) and DBA/2J (D2 or D). DBA/2J has been partially sequenced (approximately 1.5x coverage by D by Celera Genomics). Significant genomic sequence data for AKR is not currently available. Chromosomes of the two parental strains have recombined in the different AKXD strains. All of these strains are available from The Jackson Laboratory as cryopreserved stocks. For additional background on recombinant inbred strains, please see http://www.nervenet.org/papers/bxn.html.


About the tissue used to generate this set of data:
Mammary tumors used in this array experiment were derived from 18 sets of AKXD x FVB/N F1 females as described above. After the primary tumor was diagnosed, the animals were aged an additional 40 days to permit metastatic progression. Females were sacrificed and mammary tumors were harvested. Samples were processed and arrayed on Affymetrix M430A and M430B arrays. The majority of the samples were assayed on arrays obtained from the same lot number.


About the array platform:
All samples were processed and arrayed in the Laboratory of Population Genetics at the NCI. The table below lists the arrays by Samples, AKXD strain and Age.

Sample

AKXD strain

Age

AKXD2957

2

98

AKXD2959

2

96

AKXD1747

3

84

AKXD3446

3

91

AKXD4225

3

83

AKXD2543

7

82

AKXD2967

7

88

AKXD3336

7

95

AKXD2685

9

113

AKXD2710

9

109

AKXD2949

9

115

AKXD2618

10

99

AKXD2620

10

99

AKXD3023

10

94

AKXD1910

11

87

AKXD2824

11

92

AKXD2825

11

103

AKXD2635

13

83

AKXD2718

13

100

AKXD2721

13

91

AKXD2632

14

99

AKXD2640

14

100

AKXD3444

14

96

AKXD1636

16

112

AKXD3688

16

80

AKXD4152

16

91

AKXD1647

18

91

AKXD2616

18

91

AKXD2804

18

80

AKXD2456

20

100

AKXD2554

20

107

AKXD2829

20

105

AKXD1610

21

98

AKXD2611

21

88

AKXD2918

21

98

AKXD2460

22

107

AKXD2461

22

94

AKXD2463

22

110

AKXD2975

23

82

AKXD2976

23

86

AKXD3955

23

90

AKXD1494

24

103

AKXD1880

24

104

AKXD3030

24

89

AKXD1607

25

110

AKXD2326

25

92

AKXD2328

25

90

AKXD2629

25

96

AKXD1756

27

100

AKXD1757

27

98

AKXD1948

27

99

AKXD1950

27

97

AKXD2968

27

94

AKXD2809

28

88

AKXD2815

28

90

AKXD3432

28

91



About data values and data processing:
Probe (cell) level data from the .CEL file: These .CEL values produced by GCOS are 75% quantiles from a set of 91 pixel values per cell.
  • Step 1: We added an offset of 1.0 to the .CEL expression values for each cell to ensure that all values could be logged without generating negative values.
  • Step 2: We took the log base 2 of each cell.
  • Step 3: We computed the Z scores for each cell.
  • Step 4: We multiplied all Z scores by 2.
  • Step 5: We added 8 to the value of all Z scores. The consequence of this simple set of transformations is to produce a set of Z scores that have a mean of 8, a variance of 4, and a standard deviation of 2. The advantage of this modified Z score is that a two-fold difference in expression level corresponds approximately to a 1 unit difference.
  • Step 6a: The 430A and 430B GeneChips include a set of 100 shared probe sets (2200 probes) that have identical sequences. These probes and probe sets provide a way to calibrate expression of the two GeneChips to a common scale. The absolute mean expression on the 430B array is almost invariably lower than that on the 430A array. To bring the two arrays into alignment, we regressed Z scores of the common set of probes to obtain a linear regression corrections to rescale the 430B arrays to the 430A array. In our case this involved multiplying all 430B Z scores by the slope of the regression and adding or subtracting a very small offset. The result of this step is that the mean of the 430A GeneChip expression is fixed at a value of 8, whereas that of the 430B chip is typically 7. Thus average of A and B arrays is approximately 7.5.
  • Step 6b: We recenter the whole set of 430A and B transcripts to a mean of 8 and a standard deviation of 2. This involves reapplying Steps 3 through 5 above but now using the entire set of probes and probe sets from a merged 430A and B data set.
Probe set data from the .CHP file: The expression data were generated using MAS5. The same simple steps described above were also applied to these values. A 1-unit difference represents roughly a two-fold difference in expression level. Expression levels below 5 are usually close to background noise levels.

About the chromosome and megabase position values:

The chromosomal locations of probe sets and gene markers on the 430A and 430B microarrays were determined by BLAT analysis using the Mouse Genome Sequencing Consortium May 2004 (mm5) assembly (see http://genome.ucsc.edu/cgi-bin/hgBlat?command=start&org=mouse). We thank Dr. Yan Cui (UTHSC) for allowing us to use his Linux cluster to perform this analysis.


Notes:
Text originally written by Kent Hunter and Robert W. Williams, July 2004. Updated by RWW, Nov 6, 2004.


Experiment Type:


Contributor:


Citation:


Data source acknowledgment:
All of the NCI mammary mRNA M430A and M430B data sets have been generated by Kent Hunter at the Laboratory of Population Genetics at the National Cancer Institute in Bethesda. For contact and citations and other information on these data sets please review the INFO pages and contact Dr. Hunter regarding use of this data set in publications or projects.


Study Id:
9

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