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Genotype Dataset

Download the genotype dataset from the 1000 Genomes project phase 3


mkdir genotype
wget ftp://ftp.1000genomes.ebi.ac.uk/vol1/ftp/release/20130502/ALL.chr{1..22}.phase3_shapeit2_mvncall_integrated_v5a.20130502.genotypes.vcf.gz

Clean the genotype files with vcftools

# keep the 455 individuals who are reported in both the 1000 Genome Project and Geuvadis
module load vcftools
for i in `seq 1 22`
do
   vcftools --gzvcf /genotype/phase3/ALL.chr$i.phase3_shapeit2_mvncall_integrated_v5a.20130502.genotypes.vcf.gz --keep 1000g.ind.sample.txt --recode --out /genotype/phase3/chr$i.1000gphase3.455 
done

# exclude rare (less than 0.01 frequency) variants 
vcftools --vcf /genotype/phase3/chr$i.1000gphase3.455.recode.vcf --maf 0.01 --max-maf 0.99 --recode --out /genotype/phase3/chr$i.1000gphase3.455.0.01

# keep only bi-allelic variants
vcftools --vcf /genotype/phase3/chr$i.1000gphase3.455.0.01.recode.vcf --min-alleles 2 --max-alleles 2 --recode --out /genotype/phase3/chr$i.1000gphase3.455.0.01.biallelic
Identify covariates (genetic and non-genetic)

# Convert vcf file to plink format
plink --vcf chr22.1000gphase3.455.0.01.recode.vcf --make-bed --out chr22.1000gphase3.455.0.01.recode.bed

# Run pca
plink --bfile chr22.1000gphase3.455.0.01.recode.bed --pca --out
# Plot pca
library(ggplot2)
ggplot(data=pca, aes(V3,V4)) + geom_point()

Gene Expression Dataset

Gene expression quantification with Kallisto

# Download the fastq dataset from the Geuvadis project
# sample information https://www.ebi.ac.uk/arrayexpress/files/E-GEUV-1/
# fastq files ftp://ftp.sra.ebi.ac.uk/vol1/fastq/
 
csvfile=getfastq.csv
for line in `cat ${csvfile} | grep -v ^#`
do
  url=`echo ${line} | cut -d ',' -f 2`
  wget ${url}
done

#FastQC - quality check

module load fastqc
fastqc *.fastq.gz -o /fastqc_out/

module load multiqc
multiqc . -f

#Kallisto - make index files - pseudomapping
module load kallisto
wget ftp://ftp.ensembl.org/pub/grch37/current/fasta/homo_sapiens/cdna/Homo_sapiens.GRCh37.cdna.all.fa.gz
gunzip Homo_sapiens.GRCh37.cdna.all.fa.gz
kallisto index -i human.GRCh37.cdna.all.idx Homo_sapiens.GRCh37.cdna.all.fa

wget https://github.com/pachterlab/kallisto-transcriptome-indices/releases/download/ensembl-96/homo_sapiens.tar.gz
gunzip Homo_sapiens
# homo_sapiens/transcriptome.idx
# Gene expression quantification for all samples with Kallisto

module load kallisto
csvfile=1000g.sample.csv
for line in `cat ${csvfile} | grep -v ^#`
do
  file=`echo ${line} | cut -d ',' -f 1`
  kallisto quant -i human.GRCh37.cdna.all.idx -o kallisto/${file}.kallisto -n 100 -t 32 fastq2/${file}.1.fastq.gz fastq2/${file}.2.fastq.gz
done

Generate “sample - gene expression” matrix file from the kallisto output

library(tximport)
library(biomaRt)
update.packages()
install.packages("rlang")

## convert transcripts into genes
mart <- useDataset("hsapiens_gene_ensembl", useMart("ensembl", host="grch37.ensembl.org"))
df <- read.table("kallisto/HG00096.kallisto/abundance.tsv", header = TRUE,sep = "\t")
genes <- df$target_id

G_list <- getBM(filters= "ensembl_transcript_id_version", attributes=c('ensembl_transcript_id_version','ensembl_gene_id'),mart= mart,values=genes)
head(G_list)
write.csv(G_list, file = "transcripts.to.genes2.csv", append = FALSE, quote = FALSE, sep = ",",
          eol = "\n", na = "NA", dec = ".", row.names = FALSE,
          col.names = FALSE, qmethod = "double",
          fileEncoding = "")


# summarize (gene expression) data from each individual
samples <-read.csv("1000g.EUR.sample.csv",header=TRUE)
files <- file.path(dir, "kallisto", samples$kallisto, "abundance.tsv")
names(files) <- paste0(samples$X)
all(file.exists(files))
txi <- tximport(files, type = "kallisto", tx2gene = tx2gene, txOut = FALSE, ignoreAfterBar = TRUE)

write.table(txi$est_counts,sep="\t", file = "EUR.counts.tsv")
write.table(txi$tpm,sep="\t", file = "EUR.TPM.tsv")

Add gene annotations to the gene expression matrix file

library('biomaRt')
mart <- useDataset("hsapiens_gene_ensembl", useMart("ensembl", host="grch37.ensembl.org"))
df <- read.csv(file.choose(), header = T, sep = ",") 
gene <- df$gene
G_list <- getBM(filters= "ensembl_gene_id", attributes=c('ensembl_gene_id', 'hgnc_symbol','description','chromosome_name','start_position','end_position'),mart= mart,values=gene)
G_list2<-merge(df,G_list,by.x="gene",by.y="ensembl_gene_id",all.x=T)
write.csv(G_list2, file = "EUR.gene.TPM.csv")


## only genes with CPM (counts per million)>0.5 in more than half of the total samples 
## are kept for further analysis to avoid false positives in the eQTL
d1  <- read.table("EUR.counts.tsv", header = T,row.names=1,sep = "\t")
d1_scaled <- apply(d1, 2, function(x){x/sum(x)*1000000})
d1_cleaned<-d1_scaled[rowSums(d1_scaled > 0.5) > length(d1[1,])/2, ]

write.csv(d1_cleaned, file = "EUR.CPM.survived.csv")

Scale the gene expression matrix

matall<-read.table(file = 'Yoruba.TPM.filtered.tsv', sep = '\t', header = T,row.names=1)
matall<-as.matrix(matall,row.names=1,header=T)
head(matall)
matfilter <- matall[rowSums(matall) > 90,]
hist(mat[,1])
hist(mat[1,],breaks=20)
mat<-normalize.quantiles(matfilter)
mat<-scale (mat)
tmat<-t(mat)
stmat<-scale (tmat)
mat1<-t(stmat)
head(mat1)
hist(mat1[,1])
hist(mat1[1,],breaks=40)
class(mat)
colnames(mat)<-matal
write.csv(mat1, file = "Yoruba.TPM.scaled.csv")

Identify genetic covariates

# Convert vcf file to plink format
plink --vcf chr22.1000gphase3.455.0.01.recode.vcf --make-bed --out chr22.1000gphase3.455.0.01.recode.bed

# Run pca
plink --bfile chr22.1000gphase3.455.0.01.recode.bed --pca --out

# Plot pca
library(ggplot2)
ggplot(data=pca, aes(V3,V4)) + geom_point()

Identify sarrogate variables

#  surrogate variable analysis
library(sva)
mm <- model.matrix(~ population, colData(ddsTxi))
mm0 <- model.matrix(~ 1, colData(ddsTxi))
norm.cts <- norm.cts[rowSums(norm.cts) > 10,]
fit <- svaseq(norm.cts, mod=mm, mod0=mm0)
# 50 SVs are found. I use 7 SVs
sva7 = sva(norm.cts , mm, mm0, n.sv=7)
write.csv(sva7$sv[,1:7], file = "sva7.csv")

Differentially Expressed Gene Analysis

library("DESeq2")
colData <-read.csv("1000g.sample.csv",header = T,row.names=1)
class(colData$date)
colData$date1<-factor(colData$date)


ddsTxi <- DESeqDataSetFromTximport(txi,
                                   colData = colData,
                                   design = ~ sex+population+performer)

colData <-read.csv("1000g.EUR.YRI.csv",header = T,row.names=1)

ddsEurYri <- DESeqDataSetFromTximport(txi,
                                   colData = colData,
                                   design = ~ sex+population+V1+V2+V3+V4+V5+V6+V7)

keep <- rowsum(counds(ddsEurYri)) >=455
ddsEurYri <- ddsEurYri[keep,]
ddsEY<-DESeq(ddsEurYri)
deg <- results(ddsEY, contrast=c("population","EUR","Yoruba"))
write.csv(deg, file = "E-GEUV_EUR_Yoruba.csv")

Cis-eQTL Mapping Analysis

# prepare input bed.gz and index files
module load bedtools
bedtools sort -i British.gene.TPM.bed -header > British.gene.TPM.sorted.bed
bgzip British.gene.TPM.sorted.bed && tabix -p bed British.gene.TPM.sorted.bed.gz


# prepare input vcf.gz and index files
module load htslib 
module load tabix
for i in `seq 1 22`
do
    bgzip genotype/phase3/chr$i.1000gphase3.Yoruba.0.01.biallelic.recode.vcf  && tabix -p vcf genotype/phase3/chr$i.1000gphase3.Yoruba.0.01.biallelic.recode.vcf.gz
done

for i in `seq 1 22`
do
    bgzip genotype/phase3/chr$i.1000gphase3.EUR.0.01.biallelic.recode.vcf  && tabix -p vcf genotype/phase3/chr$i.1000gphase3.EUR.0.01.biallelic.recode.vcf.gz
done

# run fastQTL
## https://github.com/francois-a/fastqtl


for i in `seq 1 22`
do
  ./bin/fastQTL.static fastQTL --vcf /project2/xuanyao/marie/E-GEUV-1/genotype/phase3/chr$i.1000gphase3.EUR.0.01.biallelic.recode.vcf.gz --bed GEUV/EUR.gene.TPM.sorted.bed.gz --region $i:1-249250621  --threshold 0.001 --permute 1000 --out GEUV/EUR.chr$i.permute.0.001.txt --cov GEUV/EUR.cov.txt --normal
done


for i in `seq 1 22`
do
  ./bin/fastQTL.static fastQTL --vcf /project2/xuanyao/marie/E-GEUV-1/genotype/phase3/chr$i.1000gphase3.Yoruba.0.01.biallelic.recode.vcf.gz --bed GEUV/Yoruba.gene.TPM.sorted.bed.gz --region $i:1-249250621  --threshold 0.001 --permute 1000 --out GEUV/Yoruba.chr$i.permute.0.001.txt --cov GEUV/Yoruba.cov.txt --normal
done

cleaning and formatting the eQTL result

setwd("/project2/xuanyao/marie/E-GEUV-1")
library(ggplot2)
library("ggrepel")
library("plyr")
library(gplots)
library(reshape2)


## remove multi-allelic SNPs reported as bi-allelic SNPs which confuse the result
EUR1<-subset(EUR2, 
               EUR2$gene.SNP!="ENSG00000188659.rs542232278"&
               EUR2$gene.SNP!="ENSG00000255769.rs145926341"&
               EUR2$gene.SNP!="ENSG00000255769.rs371891811"&
               EUR2$gene.SNP!="ENSG00000259328.rs145926341"&
               EUR2$gene.SNP!="ENSG00000259323.rs145926341"&
               EUR2$gene.SNP!="ENSG00000259472.rs145926341"&
               EUR2$gene.SNP!="ENSG00000103942.rs1610794"&
               EUR2$gene.SNP!="ENSG00000103342.rs140839133"&
               EUR2$gene.SNP!="ENSG00000159202.rs77094622"&
               EUR2$gene.SNP!="ENSG00000189050.rs112549034"&
               EUR2$gene.SNP!="ENSG00000108592.rs138776605"&
               EUR2$gene.SNP!="ENSG00000256771.rs10650867"&
               EUR2$gene.SNP!="ENSG00000134330.rs139337028"&
               EUR2$gene.SNP!="ENSG00000125991.rs139252705"&
               EUR2$gene.SNP!="ENSG00000214078.rs142898689"&               
               EUR2$gene.SNP!="ENSG00000087586.rs5842156"&
               EUR2$gene.SNP!="ENSG00000171522.rs139036988"&
               EUR2$gene.SNP!="ENSG00000196284.rs112143344"&
               EUR2$gene.SNP!="ENSG00000135316.rs71553453"&
               EUR2$gene.SNP!="ENSG00000232559.rs377632592"&
               EUR2$gene.SNP!="ENSG00000131558.rs141161799"&
               EUR2$gene.SNP!="ENSG00000162441.rs36126617"&
               EUR2$gene.SNP!="ENSG00000162441.rs151178549"&
               EUR2$gene.SNP!="ENSG00000142794.rs35506192"&
               EUR2$gene.SNP!="ENSG00000142794.rs145038894"&
               EUR2$gene.SNP!="ENSG00000116128.rs10657777"&
               EUR2$gene.SNP!="ENSG00000117280.rs149256505"&
               EUR2$gene.SNP!="ENSG00000107719.rs138584752"&
               EUR2$gene.SNP!="ENSG00000198561.rs142865693"&
               EUR2$gene.SNP!="ENSG00000087365.rs5792377"&
               EUR2$gene.SNP!="ENSG00000162341.rs111786372"&
               EUR2$gene.SNP!="ENSG00000110092.rs59333593"&
               EUR2$gene.SNP!="ENSG00000111215.rs61604574"&
               EUR2$gene.SNP!="ENSG00000165502.rs141634854"&
               EUR2$gene.SNP!="ENSG00000104093.rs138911097")


YRI1<-subset(YRI2, YRI2$gene.SNP!="ENSG00000143106.rs545041240"&
               YRI2$gene.SNP!="ENSG00000078403.rs528760884"&
               YRI2$gene.SNP!="ENSG00000167996.rs150035626"&
               YRI2$gene.SNP!="ENSG00000111252.rs367797687"&
               YRI2$gene.SNP!="ENSG00000172458.rs112879834"&
               YRI2$gene.SNP!="ENSG00000183044.rs367630500"& 
               YRI2$gene.SNP!="ENSG00000154874.rs138555657"&
               YRI2$gene.SNP!="ENSG00000011132.rs71166969"&
               YRI2$gene.SNP!="ENSG00000125991.rs142898689"&
               YRI2$gene.SNP!="ENSG00000198832.rs35065681"&
               YRI2$gene.SNP!="ENSG00000128268.rs142897975"&
               YRI2$gene.SNP!="ENSG00000161013.rs71591436"&
               YRI2$gene.SNP!="ENSG00000170727.rs60257564")

sessionInfo()
R version 4.3.1 (2023-06-16)
Platform: x86_64-apple-darwin20 (64-bit)
Running under: macOS Sonoma 14.6.1

Matrix products: default
BLAS:   /Library/Frameworks/R.framework/Versions/4.3-x86_64/Resources/lib/libRblas.0.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.3-x86_64/Resources/lib/libRlapack.dylib;  LAPACK version 3.11.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: Europe/Oslo
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] workflowr_1.7.1

loaded via a namespace (and not attached):
 [1] vctrs_0.6.5       httr_1.4.7        cli_3.6.2         knitr_1.45       
 [5] rlang_1.1.3       xfun_0.42         stringi_1.8.3     processx_3.8.3   
 [9] promises_1.3.0    jsonlite_1.8.8    glue_1.7.0        rprojroot_2.0.4  
[13] git2r_0.33.0      htmltools_0.5.7   httpuv_1.6.15     ps_1.7.6         
[17] sass_0.4.8        fansi_1.0.6       rmarkdown_2.26    jquerylib_0.1.4  
[21] tibble_3.2.1      evaluate_0.23     fastmap_1.1.1     yaml_2.3.8       
[25] lifecycle_1.0.4   whisker_0.4.1     stringr_1.5.1     compiler_4.3.1   
[29] fs_1.6.3          pkgconfig_2.0.3   Rcpp_1.0.12       rstudioapi_0.15.0
[33] later_1.3.2       digest_0.6.34     R6_2.5.1          utf8_1.2.4       
[37] pillar_1.9.0      callr_3.7.5       magrittr_2.0.3    bslib_0.6.1      
[41] tools_4.3.1       cachem_1.0.8      getPass_0.2-4