README.md

In NWPU-903PR/m6Aexpress: Predicting context-specific m6A regulation of gene expression

Installation Instructions

The m6A-express package is supported by R 3.5.3 or newer versions. First, you need to install the exomePeak package for m6A peak calling:

if (!requireNamespace("BiocManager", quietly = TRUE))
    install.packages("BiocManager")

BiocManager::install(c("Rsamtools","GenomicAlignments","GenomicRanges",
                       "GenomicFeatures","rtracklayer","DESeq2","apeglm","RMariaDB"))

install.packages("https://www.bioconductor.org/packages/3.8/bioc/src/contrib/exomePeak_2.16.0.tar.gz", repos = NULL, type="source")

Then, please install the QNB package for identifying differential m6A peaks:

install.packages("locfit")
install.packages("https://cran.r-project.org/src/contrib/Archive/QNB/QNB_1.1.11.tar.gz", repos = NULL, type="source")

Installed the reticulate pacakge to call python code in R

install.packages("reticulate")
##install miniconda to install specific python package
library(reticulate)
install_miniconda()
##install specific python package in R
py_install("statsmodels"); py_install("pandas"); py_install("scipy"); py_install("numpy")

Before installing the m6Aexpress package, you should install the following R package:

if (!requireNamespace("BiocManager", quietly = TRUE))  install.packages("BiocManager")
##If the R version R>=4.0, the DESeq package should be installed by
##for Linux installation
install.packages("https://www.bioconductor.org/packages/3.11/bioc/src/contrib/DESeq_1.39.0.tar.gz", repos = NULL, type="source")
##for Windows installation
install.packages("https://www.bioconductor.org/packages/3.11/bioc/bin/windows/contrib/4.0/DESeq_1.39.0.zip", repos = NULL, type="source")
##If the R version R>=3.5.3, the DESeq package should be installed by
BiocManager::install('DESeq')
##Install some annotation packages
BiocManager::install(c('org.Hs.eg.db', 'org.Mm.eg.db', 'TxDb.Hsapiens.UCSC.hg19.knownGene', 
                       'TxDb.Mmusculus.UCSC.mm10.knownGene','AnnotationDbi'))

Now, the m6A-express package can be installed by the following R commands:

if (!requireNamespace("devtools", quietly = TRUE))
    install.packages("devtools")
devtools::install_github("NWPU-903PR/m6Aexpress")
library(m6Aexpress)

Usage Example

m6A-express considers a scenario where transcriptome-wide m6A under different conditions (treated/disease vs control; different tissues/infection stages) are profiled by MeRIP-seq. Note that m6A-express is not restricted to MeRIP-seq but can be applied to any high-throughput methods such as MAZTER-seq or nanopore sequencing that quantify m6A stoichiometry. m6A-express assumes that for an m6A site that regulates mRNA expression, the change of its m6A level is predictive of the change in the expression level of the methylated gene, where the m6A level is quantified by MeRIP-seq IP reads and the expression is measured by MeRIP-seq Input reads. m6A-express is an algorithm designed to assess the degree to which such a predictive relationship exists between m6A levels and gene expressions for the specific conditions under consideration.

Before applying m6A-express, m6A peaks are first identified from each MeRIP-seq sample using exomePeak (Figure 1 of the paper). The m6A intensity for each gene that harbors m6A peaks is computed (Peak Calling and Quantifying Subsection). m6A-express then selects candidate genes based on the following criteria: when two conditions (treated vs. control) are considered, candidate genes are differential expression genes that harbor differential m6A peaks (or DE-DM genes); otherwise, when there are more than two conditions (multiple tissue types or time points), candidate genes are those that contain highly variable m6A peaks (HVPs). Afterward, m6A-express is applied to all the candidate genes. The candidate genes test significant for FDR<0.05 by the Wald test are termed m6A-reg-exp genes, whose m6A intensities are predicted to regulate their gene expressions. Among the outputs of m6A-express are a list of m6A-reg-exp genes, their associated regulatory mode and strength (β1), the methylation intensities, and the gene expression levels.

The following codes show how to use the m6A-express package (named m6Aexpress) to obtain m6A-reg-exp genes genes for two or more conditions. Both step-by-step analysis and one-step prediction are detailed.

Step by Step Analysis

For two (case-control) conditions

Peak calling for methylation sites in DE-DM context and obtain consisten peak sites

f1 <- system.file("extdata", "IP1.bam", package="m6Aexpress")
f2 <- system.file("extdata", "IP2.bam", package="m6Aexpress")
f3 <- system.file("extdata", "IP3.bam", package="m6Aexpress")
f4 <- system.file("extdata", "IP4.bam", package="m6Aexpress")
f5 <- system.file("extdata", "Input1.bam", package="m6Aexpress")
f6 <- system.file("extdata", "Input2.bam", package="m6Aexpress")
f7 <- system.file("extdata", "Input3.bam", package="m6Aexpress")
f8 <- system.file("extdata", "Input4.bam", package="m6Aexpress")
IP_BAM <- c(f1,f2)
INPUT_BAM <- c(f5,f6)
TREATED_IP_BAM <- c(f3,f4)
TREATED_INPUT_BAM <- c(f7,f8)
#Input the gene annotation file  
gtf <- system.file("extdata", "hg19toy.gtf", package="m6Aexpress")
#Obtain the consistent peak sites
Get_peak_infor <- Get_peakinfor(IP_BAM, INPUT_BAM,TREATED_IP_BAM, TREATED_INPUT_BAM, GENE_ANNO_GTF=gtf)

Calling differential methylated (DM) peaks among the consistent peaks

DM_sites_infor <- DM_detect(peak_inform=Get_peak_infor,DM_CUTOFF_TYPE="pvalue",num_ctl=2, diff_peak_pvalue=0.05)

Calculate the methylation intensity for each gene with DM peaks

gene_methyintensity <- gene_methy_intensity(peak_inform=DM_sites_infor,txdbinfor=NA,GENE_ANNO_GTF=gtf)

Obtain their gene expression for INPUT samples

get_gene_express <- Get_express_data(INPUT_BAM=c(INPUT_BAM,TREATED_INPUT_BAM ), 
                                      isPairedEnd=FALSE,GENE_ANNO_GTF = gtf,isGTFAnnotationFile=TRUE)

Identify the differential expression gene

obtain_DEgene <- Select_DEgene(gene_count_infor=get_gene_express,
                               cond1="control", 
                               cond2="treated",
                               num_cond1=2, 
                               num_cond2=2,
                               DIFF_GENE_cutoff_FDR=0.05,
                               DE_CUTOFF_TYPE="padj") 

Select genes with both differential expression and differential methylation

expr_methy_gene <- match_expr_methy(gene_count_infor=obtain_DEgene, 
                                     gene_methy_infor=gene_methyintensity,
                                    OUTPUT_DIR=NA)

Predict m6A-reg-exp genes

m6Aexpress_result <- m6A_Express_model(Input_file=expr_methy_gene,
                                           CUTOFF_TYPE="FDR", 
                                            FDR=0.05)

Add differential expression and differential methylation in the result

m6A_express_addLFC_DDM <- add_LFC_DDM(expre_methyre=m6Aexpress_result, 
                                    DE_gene=obtain_DEgene, methy_intensity=gene_methyintensity,
                                    num_cond1=2, OUTPUT_DIR=NA)

For more than two conditions

Peak calling

IP_BAM <- c(f1,f2,f3,f4)
INPUT_BAM <- c(f5,f6,f7,f8)
Get_peak_infor <- Get_peakinfor(IP_BAM, INPUT_BAM, GENE_ANNO_GTF=gtf)

Detect highly variable peaks across multiple conditions

HVP_infor <- obtain_HVP_sites(peak_inform=Get_peak_infor,CV_values=0.3,
                               num_sample_subgroup=c(2,2))

Calculate the methylation intensity for each gene with highly variable peaks

gene_methyintensity <- gene_methy_intensity(peak_inform=HVP_infor,GENE_ANNO_GTF=gtf)

Obtain gene expressions from INPUT samples in each condition

get_gene_express <- Get_express_data(INPUT_BAM=c(INPUT_BAM), 
                                      isPairedEnd=FALSE,
                                      GENE_ANNO_GTF = gtf)

Select genes with expression and methylation intensity of highly variable peaks

expr_methy_gene <- match_expr_methy(gene_count_infor=get_gene_express, 
                                     gene_methy_infor=gene_methyintensity,
                                    OUTPUT_DIR=NA)

Predicate m6A-reg-exp gene by m6Aexpress model in tissue-specific context

m6A_Express_model(Input_file=expr_methy_gene,
                     CUTOFF_TYPE="FDR", 
                      FDR=0.05)

On step to predicate m6A-reg-exp gene

For two conditions:

IP_BAM <- c(f1,f2)
TREATED_IP_BAM <- c(f3,f4) 
INPUT_BAM <- c(f5,f6) 
TREATED_INPUT_BAM <- c(f7,f8) 
m6A_reg_exp_gene <- m6Aexpress(express_data=INPUT_BAM, treated_express_data=TREATED_INPUT_BAM, 
                                    IP_BAM=IP_BAM, TREATED_IP_BAM=TREATED_IP_BAM, INPUT_BAM=INPUT_BAM, 
                                    TREATED_INPUT_BAM=TREATED_INPUT_BAM,annot_type="hg19", GENE_ANNO_GTF=gtf,
                                    isGTFAnnotationFile=TRUE, pvalue=0.05,mode="DE-DM")

For more than two conditions

IP_BAM <- c(f1,f2,f3,f4)
INPUT_BAM <- c(f5,f6,f7,f8) 
m6A_reg_exp_gene <- m6Aexpress(express_data=INPUT_BAM, IP_BAM=IP_BAM, INPUT_BAM=INPUT_BAM, 
                                annot_type="hg19", GENE_ANNO_GTF=gtf,isGTFAnnotationFile=TRUE, 
                                pvalue=0.05,mode="HVP", CV_values = 0.3, num_sample_subgroup=c(2,2))

NWPU-903PR/m6Aexpress documentation built on Dec. 17, 2021, 5:18 a.m.