This is continuation of the WGBS analysis I’ve been running on Ronit’s data. The previous post can be found here. Last time I looked at the MultiQC report and quantified differences in %mCpG between diploid and triploid cgigas after desiccation at 27C for 24hrs.
List of the progress so far:
- Completed bismark on mox. The output was then transferred to gannet by running the rsync command as outlined in the previous post. The output is available here.
- The MultiQC report can be found here.
Goal for today:
Use MethylKit to identify differentially methylated loci (DMLs) between diploid and triploid cgigas after desiccation stress. I’ll be following Yaamini’s walkthrough in this post to process *.deduplicated.sorted.bam files, running an modified version of this R markdown file that produces results using 1x, 3x, and 5x coverage.
Step 1: Get MethylKit installed
My R file can be found here. After some version compatibility issues, I was able to get “devtools” and “methylkit” installed and up-to-date by running R Studio as an administrator and running the following code chunk, opting to update all:
install.packages("devtools") #Install the devtools package library(devtools) #Load devtools if (!requireNamespace("BiocManager", quietly = TRUE)) install.packages("BiocManager") BiocManager::install(version = "3.12") BiocManager::install(c("GenomicFeatures", "AnnotationDbi","methylKit")) library(methylKit) #Load methylkit browseVignettes("methylKit") #methylKit manual
The important part seemed to be to install BiocManager version 3.12, as it is compatible with R version 4.0.4.
Step 2: Set paths to *.deduplicated.sorted.bam files
The next step was to generate a list of files (and their locations) to be analyzed. Since my files were on gannet in this folder and I plan on running the R script locally for the time being, I downloaded the files on my spare local data drive (E:/). From there, I mapped the location as follows:
analysisFiles <- list("E:/bam_files/zr3534_1_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_2_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_3_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_4_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_5_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_6_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_7_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_8_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_9_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam", "E:/bam_files/zr3534_10_R1.fastp-trim.20201202_bismark_bt2_pe.deduplicated.sorted.bam")
This approach isn’t really ideal - I should figure out a way to import directly from gannet in the future.
Step 3: Create sampleID list and treatment variable
Next I used this quick and dirty script to generate names (just numbers 1-10 for now), and treatmentSpecifications (0=diploid,1=triploid)
sample.IDs <- list("1", "2", "3", "4", "5", "6", "7", "8", "9", "10") #Create list of sample IDs treatmentSpecification <- c(rep(0, times = 5), rep(1, times = 5)) # Specify which treatment the samples were from. All animals were subjected to desiccation. 0 = diploid, 1 = triploid
Step 4: Run processBismarkAln
Next I will run processBismarkAln to set different coverage metrics (1x, 3x, and 5x) in the ‘mincov’ argument, using the folloiwng code.
processedFilesCov1 <- processBismarkAln(location = analysisFiles, sample.id = sample.IDs, assembly = "v3", read.context = "CpG", mincov = 1, treatment = treatmentSpecification) #Process files for CpG methylation using 1x coverage. First 5 files were diploid, and the second 5 are triploid.
This chunk was run with mincov = 1, 3, or 5. This step took a long time! On my desktop machine (Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz), it averaged 1 sample every 30 mins.
I know that Yaamini is working on a mox script for this step. I’ll link it here when/if she finishes it.