geod24243

María Lairón y Guillermo Ayala

2024-04-02

Data

The data set can be found at GEO gse24243.

Packages

pacman::p_load(AnnotationDbi,ArrayExpress,mouse4302.db,pd.mouse430.2)

Download data from ArrayExpress

Using package ArrayExpress.

geod24243raw = ArrayExpress("E-GEOD-24243")
save(geod24243raw,file=paste0(dirTamiData,"geod24243raw.rda"))
load(paste0(dirTamiData,"geod24243raw.rda"))

Let us see the class.

class(geod24243raw)
[1] "ExpressionFeatureSet"
attr(,"package")
[1] "oligoClasses"

Robust multichip average

geod24243 = rma(geod24243raw)

Making an ExpressionSet

  1. Experimental data.
datosexperimento = new('MIAME',name='Flowers MT, Scheisser K, Dawson JA,
                       Kendziorski C, Ntambi JM',
                       lab='James Ntambi',
                       contact ='mtflowers@wisc.edu',
title = 'Metabolic changes in skin caused by Scd1 deficiency: a focus on
retinol metabolism.',
abstract = 'To help elucidate the metabolic changes in the skin that
contribute to the obesity resistance and skin pathology in mice lacking Scd1, we performed microarray analysis of skin gene expression in male skin Scd1 knockout (SKO) and Scd1 flox/flox control (Lox) mice fed a standard rodent diet. We identified an extraordinary number of differentially expressed genes that support the previously documented histological observations of sebocyte atrophy, inflammation and epidermal hyperplasia in SKO mice. Additionally, transcript levels were reduced in skin of SKO mice for genes involved in fatty acid synthesis, elongation and desaturation, which may be attributed to decreased abundance of key transcription factors including SREBP1c, ChREBP and LXR. Conversely, genes involved in cholesterol synthesis were increased, suggesting an imbalance between skin fatty acid and cholesterol synthesis. Unexpectedly, we observed a robust elevation in skin retinol, retinoic acid and retinoic acid-induced genes in SKO mice. These results highlight the importance of monounsaturated fatty acid synthesis for maintaining retinol homeostasis and point to disturbed retinol metabolism as a novel contributor to the Scd1 deficiency-induced skin pathology. We analyzed dorsal skin gene expression in non-fasted 8-9 week old male skin Scd1 knockout (SKO) mice (n=3) and Scd1flox/flox (Lox) control mice (n=3)on a C57BL/6J background using Affymetrix 430 2.0 microarrays.', 
url = 'https://www.ebi.ac.uk/arrayexpress/experiments/E-GEOD-24243/'
)    
experimentData(geod24243) = datosexperimento  
  1. Define a new experimental factor.
type = factor(c(0,0,0,1,1,1),levels = 0:1,labels=c("SKO","LOX"))
pd = data.frame(type)
rownames(pd) = colnames(geod24243)
pData(geod24243) = pd
  1. Annotation

Let us simplify the problem and we are going to consider just the correspondences with ENTREZID.

a = AnnotationDbi::select(mouse4302.db, keys=featureNames(geod24243), 
                          column=c("ENTREZID"),
                          keytype="PROBEID")
  1. Multiple correspondences
  • How many features have after normalization?
nrow(geod24243)

We have multiple correspondences.

  • How many and which are the probes corresponding with more than one gene.
b = which(table(a[,1]) > 1)
length(b)
head(b)
  • For the probes names(b) we have more than one gene.
sel = is.element(a[,1],names(b))
table(table(a[sel,1]))
  • A possibility is to use the first correspondence in the original data.frame.
c1 = match(unique(a[,1]),a[,1])
a1 = a[c1,]
  • Let us see if each ENTREZID identifier has a unique PROBEID identifier.
table(table(a1[,2]) >1)
  • It is not true.
  • Let us choose one probe per ENTREZID.
c2 = match(unique(a1[,2]),a1[,2])
a2 = a1[c2,]
dim(a2)
  • Is there a 1-1 correspondence?
length(unique(a2[,1])) == length(unique(a2[,2])) 
  • Now we want to establish the correspondence between PROBEID with ENTREZID and ENSEMBL.
a = AnnotationDbi::select(mouse4302.db, keys=featureNames(geod24243), 
                          column=c("ENTREZID","ENSEMBL"),
                          keytype="PROBEID")
View(a)
b = match(featureNames(geod24243),a[,"PROBEID"])
fData(geod24243) = a[b,]

Let us see the dimension of a.

dim(a)
c1 = match(unique(a[,1]),a[,1])
a1 = a[c1,]
c2 = match(unique(a1[,2]),a1[,2])
a2 = a1[c2,]

The ENSEMBL identifiers are not unique.

table(table(a1[,3]) >1)
  • It is important to choose the primary identifier for later use.
  1. Saving data.
save(geod24243,file ="geod24243.rda")