Bedtools是處理基因組信息分析的強大工具集合,本文列出自己學習其官方文檔的幾個點,對後面計算不同樣品peak相似性的腳本做了下更新和調整,使用起來更爲簡單方便。
內容摘要
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區域註釋,如peak註釋,peak分佈分析,peak與調控元件交集等。
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區域合併,如求算多樣品peak合集,或合併重疊區域
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區域互補,如得到非基因區
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利用比對結果對測序廣度和深度評估
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多樣品peak相似性計算,評估ChIP類區域結果的樣品相似性。
bedtools主要功能
bedtools: flexible tools for genome arithmetic and DNA sequence analysis.
usage: bedtools <subcommand> [options]
The bedtools sub-commands include:
[ Genome arithmetic ]
intersect Find overlapping intervals in various ways.
求區域之間的交集,可以用來註釋peak,計算reads比對到的基因組區域
不同樣品的peak之間的peak重疊情況。
window Find overlapping intervals within a window around an interval.
closest Find the closest, potentially non-overlapping interval.
尋找最近但可能不重疊的區域
coverage Compute the coverage over defined intervals.
計算區域覆蓋度
map Apply a function to a column for each overlapping interval.
genomecov Compute the coverage over an entire genome.
merge Combine overlapping/nearby intervals into a single interval.
合併重疊或相接的區域
cluster Cluster (but don't merge) overlapping/nearby intervals.
complement Extract intervals _not_ represented by an interval file.
獲得互補區域
subtract Remove intervals based on overlaps b/w two files.
計算區域差集
slop Adjust the size of intervals.
調整區域大小,如獲得轉錄起始位點上下游3 K的區域
flank Create new intervals from the flanks of existing intervals.
sort Order the intervals in a file.
排序,部分命令需要排序過的bed文件
random Generate random intervals in a genome.
獲得隨機區域,作爲背景集
shuffle Randomly redistrubute intervals in a genome.
根據給定的bed文件獲得隨機區域,作爲背景集
sample Sample random records from file using reservoir sampling.
spacing Report the gap lengths between intervals in a file.
annotate Annotate coverage of features from multiple files.
[ Multi-way file comparisons ]
multiinter Identifies common intervals among multiple interval files.
unionbedg Combines coverage intervals from multiple BEDGRAPH files.
[ Paired-end manipulation ]
pairtobed Find pairs that overlap intervals in various ways.
pairtopair Find pairs that overlap other pairs in various ways.
[ Format conversion ]
bamtobed Convert BAM alignments to BED (& other) formats.
bedtobam Convert intervals to BAM records.
bamtofastq Convert BAM records to FASTQ records.
bedpetobam Convert BEDPE intervals to BAM records.
bed12tobed6 Breaks BED12 intervals into discrete BED6 intervals.
[ Fasta manipulation ]
getfasta Use intervals to extract sequences from a FASTA file.
提取給定位置的FASTA序列
maskfasta Use intervals to mask sequences from a FASTA file.
nuc Profile the nucleotide content of intervals in a FASTA file.
[ BAM focused tools ]
multicov Counts coverage from multiple BAMs at specific intervals.
tag Tag BAM alignments based on overlaps with interval files.
[ Statistical relationships ]
jaccard Calculate the Jaccard statistic b/w two sets of intervals.
計算數據集相似性
reldist Calculate the distribution of relative distances b/w two files.
fisher Calculate Fisher statistic b/w two feature files.
[ Miscellaneous tools ]
overlap Computes the amount of overlap from two intervals.
igv Create an IGV snapshot batch script.
用於生成一個腳本,批量捕獲IGV截圖
links Create a HTML page of links to UCSC locations.
makewindows Make interval "windows" across a genome.
把給定區域劃分成指定大小和間隔的小區間 (bin)
groupby Group by common cols. & summarize oth. cols. (~ SQL "groupBy")
分組結算,不只可以用於bed文件。
expand Replicate lines based on lists of values in columns.
split Split a file into multiple files with equal records or base pairs.
安裝bedtools
ct@ehbio:~$ conda install bedtools
獲得測試數據集(http://quinlanlab.org/tutorials/bedtools/bedtools.html)
ct@ehbio:~$ mkdir bedtools
ct@ehbio:~$ cd bedtools
ct@ehbio:~$ url=https://s3.amazonaws.com/bedtools-tutorials/web
ct@ehbio:~/bedtools$ curl -O ${url}/maurano.dnaseI.tgz
ct@ehbio:~/bedtools$ curl -O ${url}/cpg.bed
ct@ehbio:~/bedtools$ curl -O ${url}/exons.bed
ct@ehbio:~/bedtools$ curl -O ${url}/gwas.bed
ct@ehbio:~/bedtools$ curl -O ${url}/genome.txt
ct@ehbio:~/bedtools$ curl -O ${url}/hesc.chromHmm.bed
交集 (intersect)
查看輸入文件,bed
格式,至少三列,分別是染色體
,起始位置
(0-based,
包括),終止位置
(1-based,不包括)。第四列一般爲區域名字,第五列一般爲空,第六列爲鏈的信息。更詳細解釋見http://www.genome.ucsc.edu/FAQ/FAQformat.html#format1。
自己做研究CpG島信息可以從UCSC的Table Browser獲得,具體操作見http://blog.genesino.com/2013/05/ucsc-usages/。
ct@ehbio:~/bedtools$ head -n 3 cpg.bed exons.bed
==> cpg.bed <==
chr1 28735 29810 CpG:_116
chr1 135124 135563 CpG:_30
chr1 327790 328229 CpG:_29
==> exons.bed <==
chr1 11873 12227 NR_046018_exon_0_0_chr1_11874_f 0 +
chr1 12612 12721 NR_046018_exon_1_0_chr1_12613_f 0 +
chr1 13220 14409 NR_046018_exon_2_0_chr1_13221_f 0 +
獲得重疊區域(既是外顯子,又是CpG島的區域)
ct@ehbio:~/bedtools$ bedtools intersect -a cpg.bed -b exons.bed | head -5
chr1 29320 29370 CpG:_116
chr1 135124 135563 CpG:_30
chr1 327790 328229 CpG:_29
chr1 327790 328229 CpG:_29
chr1 327790 328229 CpG:_29
輸出重疊區域對應的原始區域(與外顯子存在交集的CpG島)
ct@ehbio:~/bedtools$ bedtools intersect -a cpg.bed -b exons.bed -wa -wb > | head -5
-
chr1 28735 29810 CpG:_116 chr1 29320 29370
NR_024540_exon_10_0_chr1_29321_r 0 -
-
chr1 135124 135563 CpG:_30 chr1 134772 139696
NR_039983_exon_0_0_chr1_134773_r 0 -
-
chr1 327790 328229 CpG:_29 chr1 324438 328581
NR_028322_exon_2_0_chr1_324439_f 0 +
-
chr1 327790 328229 CpG:_29 chr1 324438 328581
NR_028325_exon_2_0_chr1_324439_f 0 +
-
chr1 327790 328229 CpG:_29 chr1 327035 328581
NR_028327_exon_3_0_chr1_327036_f 0 +
計算重疊鹼基數
ct@ehbio:~/bedtools$ bedtools intersect -a cpg.bed -b exons.bed -wo | head -10
-
chr1 28735 29810 CpG:_116 chr1 29320 29370
NR_024540_exon_10_0_chr1_29321_r 0 - 50
-
chr1 135124 135563 CpG:_30 chr1 134772 139696
NR_039983_exon_0_0_chr1_134773_r 0 - 439
-
chr1 327790 328229 CpG:_29 chr1 324438 328581
NR_028322_exon_2_0_chr1_324439_f 0 + 439
-
chr1 327790 328229 CpG:_29 chr1 324438 328581
NR_028325_exon_2_0_chr1_324439_f 0 + 439
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chr1 327790 328229 CpG:_29 chr1 327035 328581
NR_028327_exon_3_0_chr1_327036_f 0 + 439
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chr1 713984 714547 CpG:_60 chr1 713663 714068
NR_033908_exon_6_0_chr1_713664_r 0 - 84
-
chr1 762416 763445 CpG:_115 chr1 761585 762902
NR_024321_exon_0_0_chr1_761586_r 0 - 486
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chr1 762416 763445 CpG:_115 chr1 762970 763155
NR_015368_exon_0_0_chr1_762971_f 0 + 185
-
chr1 762416 763445 CpG:_115 chr1 762970 763155
NR_047519_exon_0_0_chr1_762971_f 0 + 185
-
chr1 762416 763445 CpG:_115 chr1 762970 763155
NR_047520_exon_0_0_chr1_762971_f 0 + 185
計算第一個(-a)bed區域有多少個重疊的第二個(-b)bed文件中有多少個區域
ct@ehbio:~/bedtools$ bedtools intersect -a cpg.bed -b exons.bed -c | head
chr1 28735 29810 CpG:_116 1
chr1 135124 135563 CpG:_30 1
chr1 327790 328229 CpG:_29 3
chr1 437151 438164 CpG:_84 0
chr1 533219 534114 CpG:_94 0
chr1 544738 546649 CpG:_171 0
chr1 713984 714547 CpG:_60 1
chr1 762416 763445 CpG:_115 10
chr1 788863 789211 CpG:_28 9
另外還有-v
取出不重疊的區域,
-f
限定重疊最小比例,-sorted
可以對按sort -k1,1 -k2,2n
排序好的文件加速操作。
同時對多個區域求交集 (可以用於peak的多維註釋)
# -names標註註釋來源
# -sorted: 如果使用了這個參數,提供的一定是排序好的bed文件
ct@ehbio:~/bedtools$ bedtools intersect -a exons.bed \
-b cpg.bed gwas.bed hesc.chromHmm.bed -sorted -wa -wb -names cpg gwas chromhmm \
| head -10000 | tail -10
-
chr1 27632676 27635124
NM_001276252_exon_15_0_chr1_27632677_chromhmm chr1 27633213
27635013 5_Strong_Enhancer
-
chr1 27632676 27635124
NM_001276252_exon_15_0_chr1_27632677_chromhmm chr1 27635013
27635413 7_Weak_Enhancer
-
chr1 27632676 27635124 NM_015023_exon_15_0_chr1_27632677_f
chromhmm chr1 27632613 27632813 6_Weak_Enhancer
-
chr1 27632676 27635124 NM_015023_exon_15_0_chr1_27632677_f
chromhmm chr1 27632813 27633213 7_Weak_Enhancer
-
chr1 27632676 27635124 NM_015023_exon_15_0_chr1_27632677_f
chromhmm chr1 27633213 27635013 5_Strong_Enhancer
-
chr1 27632676 27635124 NM_015023_exon_15_0_chr1_27632677_f
chromhmm chr1 27635013 27635413 7_Weak_Enhancer
-
chr1 27648635 27648882 NM_032125_exon_0_0_chr1_27648636_f cpg
chr1 27648453 27649006 CpG:_63
-
chr1 27648635 27648882 NM_032125_exon_0_0_chr1_27648636_f
chromhmm chr1 27648613 27649413 1_Active_Promoter
-
chr1 27648635 27648882 NR_037576_exon_0_0_chr1_27648636_f cpg
chr1 27648453 27649006 CpG:_63
-
chr1 27648635 27648882 NR_037576_exon_0_0_chr1_27648636_f
chromhmm chr1 27648613 27649413 1_Active_Promoter
合併區域
bedtools merge
輸入的是按sort -k1,1 -k2,2n
排序好的bed文件。
只需要輸入一個排序好的bed文件,默認合併重疊或鄰接區域。
ct@ehbio:~/bedtools$ bedtools merge -i exons.bed | head -n 5
chr1 11873 12227
chr1 12612 12721
chr1 13220 14829
chr1 14969 15038
chr1 15795 15947
合併區域並輸出此合併後區域是由幾個區域合併來的
ct@ehbio:~/bedtools$ bedtools merge -i exons.bed -c 1 -o count | head -n 5
chr1 11873 12227 1
chr1 12612 12721 1
chr1 13220 14829 2
chr1 14969 15038 1
chr1 15795 15947 1
合併相距90 nt
內的區域,並輸出是由哪些區域合併來的
# -c: 指定對哪些列進行操作
# -o: 與-c對應,表示對指定列進行哪些操作
# 這裏的用法是對第一列做計數操作,輸出這個區域是由幾個區域合併來的
# 對第4列做收集操作,記錄合併的區域的名字,並逗號分隔顯示出來
ct@ehbio:~/bedtools$ bedtools merge -i exons.bed -d 340 -c 1,4 -o count,collapse | head -4
chr1 11873 12227 1 NR_046018_exon_0_0_chr1_11874_f
chr1 12612 12721 1 NR_046018_exon_1_0_chr1_12613_f
chr1 13220 15038 3 NR_046018_exon_2_0_chr1_13221_f,NR_024540_exon_0_0_chr1_14362_r,NR_024540_exon_1_0_chr1_14970_r
chr1 15795 15947 1 NR_024540_exon_2_0_chr1_15796_r
計算互補區域
給定一個全集,再給定一個子集,求另一個子集。比如給定每條染色體長度和外顯子區域,求非外顯子區域。給定基因區,求非基因區。給定重複序列,求非重複序列等。
重複序列區域的獲取也可以用下面提供的鏈接:http://blog.genesino.com/2013/05/ucsc-usages/。
ct@ehbio:~/bedtools$ head genome.txt
chr1 249250621
chr10 135534747
chr11 135006516
chr11_gl000202_random 40103
chr12 133851895
chr13 115169878
chr14 107349540
chr15 102531392
ct@ehbio:~/bedtools$ bedtools complement -i exons.bed -g genome.txt | head -n 5
chr1 0 11873
chr1 12227 12612
chr1 12721 13220
chr1 14829 14969
chr1 15038 15795
基因組覆蓋廣度和深度
計算基因組某個區域是否被覆蓋,覆蓋深度多少。有下圖多種輸出格式,也支持RNA-seq數據,計算junction-reads覆蓋。
genome.txt
裏面的內容就是染色體及對應的長度。
# 對單行FASTA,可如此計算
# 如果是多行FASTA,則需要累加
ct@ehbio:~/bedtools$ awk 'BEGIN{OFS=FS="\t"}{\
if($0~/>/) {seq_name=$0;sub(">","",seq_name);} \
else {print seq_name,length;} }' ../bio/genome.fa | tee ../bio/genome.txt
chr1 60001
chr2 54001
chr3 54001
chr4 60001
ct@ehbio:~/bedtools$ bedtools genomecov -ibam ../bio/map.sortP.bam -bga \
-g ../bio/genome.txt | head
# 這個warning很有意思,因爲BAM中已經有這個信息了,就不需要提供了
*****
*****WARNING: Genome (-g) files are ignored when BAM input is provided.
*****
# bedgraph文件,前3列與bed相同,最後一列表示前3列指定的區域的覆蓋度。
chr1 0 11 0
chr1 11 17 1
chr1 17 20 2
chr1 20 31 3
chr1 31 36 4
chr1 36 43 6
chr1 43 44 7
chr1 44 46 8
chr1 46 48 9
chr1 48 54 10
兩個思考題:
怎麼計算有多少基因組區域被測到了?
怎麼計算平均測序深度是多少?
數據集相似性
bedtools jaccard
計算的是給定的兩個bed
文件之間交集區域(intersection)佔總區域(union-intersection)的比例(jaccard)和交集的數目(n_intersections)。
ct@ehbio:~/bedtools$ bedtools jaccard \ -a fHeart-DS16621.hotspot.twopass.fdr0.05.merge.bed \ -b fHeart-DS15839.hotspot.twopass.fdr0.05.merge.bedintersection union-intersection jaccard n_intersections81269248 160493950 0.50637 130852
小思考:1. 如何用bedtools其它工具算出這個結果?2. 如果需要比較的文件很多,怎麼充分利用計算資源?
一個辦法是使用for
循環,
雙層嵌套。這種用法也很常見,不管是單層還是雙層for循環,都有利於簡化重複運算。
ct@ehbio:~/bedtools$ for i in *.merge.bed; do \ for j in *.merge.bed; do \ bedtools jaccard -a $i -b $j | cut -f3 | tail -n +2 | sed "s/^/$i\t$j\t/"; \ done; done >total.similarity
另一個辦法是用parallel
,不只可以批量,更可以並行。
root@ehbio:~# yum install parallel.noarch# parallel 後面雙引號("")內的內容爲希望用parallel執行的命令,# 整體寫法與Linux下命令寫法一致。# 雙引號後面的 三個相鄰冒號 (:::)默認用來傳遞參數的,可多個連寫。# 每個三冒號後面的參數會被循環調用,而在命令中的引用則是根據其出現的位置,分別用{1}, {2}# 表示第一個三冒號後的參數,第二個三冒號後的參數。## 這個命令可以替換原文檔裏面的整合和替換, 相比於原文命令生成多個文件,這裏對每個輸出結果# 先進行了比對信息的增加,最後結果可以輸入一個文件中。#ct@ehbio:~/bedtools$ parallel "bedtools jaccard -a {1} -b {2} | awk 'NR> | cut -f 3 \ | sed 's/^/{1}\t{2}\t/'" ::: `ls *.merge.bed` ::: `ls *.merge.bed` >totalSimilarity.2# 上面的命令也有個小隱患,並行計算時的輸出衝突問題,可以修改爲輸出到單個文件,再cat到一起ct@ehbio:~/bedtools$ parallel "bedtools jaccard -a {1} -b {2} | awk 'NR> | cut -f 3 \ | sed 's/^/{1}\t{2}\t/' >{1}.{2}.totalSimilarity_tmp" ::: `ls *.merge.bed` ::: `ls *.merge.bed`ct@ehbio:~/bedtools$ cat *.totalSimilarity_tmp >totalSimilarity.2# 替換掉無關信息ct@ehbio:~/bedtools$ sed -i -e 's/.hotspot.twopass.fdr0.05.merge.bed//' \ -e 's/.hg19//' totalSimilarity.2
totalSimilarity.2
數據表格式如下 (數據是假的):
fMusle_leg-DS19115 fMusle_back-DS18454 0.55fMusle_leg-DS19115 fHeart-DS15643 0.4fHeart-DS15643 fHeart-DS16621 0.8fHeart-DS15643 fHeart-DS15839 0.7fHeart-DS16621 fHeart-DS15839 0.7
也可以使用下面的命令轉換成Wide format
矩陣,用高顏值可定製在線繪圖工具-第三版繪製。
# 這裏面b和c可以用一個,因爲是一個對稱陣# 如果2和3列內容不同,此腳本也可用ct@ehbio:~/bedtools$ awk 'BEGIN{OFS=FS="\t"}{a[$1, $2]=$3; b[$1]=1; c[$2]=1;}END\ {printf("ID"); for(i in c) printf("\t%s", i); \ for (i in b) {printf("%s", i); for(j in c) {printf("\t%s", a[i, j]);} print "";}}
原文檔(http://quinlanlab.org/tutorials/bedtools/bedtools.html)的命令,稍微有些複雜,利於學習不同命令的組合。使用時推薦使用上面的命令。
ct@ehbio:~/bedtools$ parallel "bedtools jaccard -a {1} -b {2} \ | awk 'NR>1' | cut -f 3 \ > {1}.{2}.jaccard" \ ::: `ls *.merge.bed` ::: `ls *.merge.bed`
This command will create a single file containing the pairwise Jaccard
measurements from all 400 tests.
find . \ | grep jaccard \ | xargs grep "" \ | sed -e s"/\.\///" \ | perl -pi -e "s/.bed./.bed\t/" \ | perl -pi -e "s/.jaccard:/\t/" \ > pairwise.dnase.txt
A bit of cleanup to use more intelligible names for each of the samples.
cat pairwise.dnase.txt \| sed -e 's/.hotspot.twopass.fdr0.05.merge.bed//g' \| sed -e 's/.hg19//g' \> pairwise.dnase.shortnames.txt
Now let’s make a 20x20 matrix of the Jaccard statistic. This will allow
the data to play nicely with R.
awk 'NF==3' pairwise.dnase.shortnames.txt \| awk '$1 ~ /^f/ && $2 ~ /^f/' \| python make-matrix.py \> dnase.shortnames.distance.matrix