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Old 10-20-2018, 01:14 PM   #1
landrjos
Junior Member
 
Location: Virginia

Join Date: Aug 2018
Posts: 3
Default R Code Differential Gene Expression

Hi All,

I was wondering if you could look over my R code for differential gene expression using EdjeR. I am looking to determine differential gene expression between wild type (WT) cells and knockout cells (KO). Three biological replicates were grown for each cell line and RNA was harvested. The paired end reads were mapped using STAR. Exon counts were obtained using feature counts. The exon counts were then used for the R code. Would this be sufficient to determine differential gene expression between WT and KO?

library("edgeR") library("gdata") library("heatmaply") library("ggplot2") library("genefilter") library("methylumi")

setwd("/Users/jwlandry2/Desktop/RNA-Seq\ ESC\ Data\ Analysis/R_Studio_Data_Sets")

counts=read.delim("BPTFKD_ESC_RNA_Seq_Counts_Final2.txt", header=T, row.names="Geneid")

head(counts)

group <- factor(c("WT","WT","WT","KO","KO","KO"))

dge = DGEList(counts=counts,group=group)

keep <- rowSums(cpm(dge)>2) >= 3 dge <- dge[keep, , keep.lib.sizes=FALSE]

Normalization
y <- calcNormFactors(dge) design <- model.matrix(~group) y <- estimateDisp(y,design) y$common.dispersion

plotMDS(y) plotBCV(y)

quasi-likelihood F-test
fit <- glmQLFit(y, design) qlf <- glmQLFTest(fit, coef=2) topTags(qlf)

output to text file
df <- qlf$table write.csv(df, 'qlf.csv')

Get normalizaed CPMs
mtx <- cpm(y, log = TRUE, normalized.lib.sizes = TRUE) mtx_to_plot <- varFilter(mtx, var.cutoff= 0.95)

Correlation matrix
IAC <- mtx_to_plot %>% cor(. , use = "pairwise.complete.obs", method = "pearson") heatmaply(IAC) %>% layout(margin=list(l=200,b=150))

Dendrogram
plot(hclust(as.dist(1-IAC), method="ward"))
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