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Calculation variant frequencies for copy number events for a cohort

Hi,

I have CNV calls of a cohort of patients in both individual VCF and GFF files.

I want to get to the rare ones, so I want to calculate frequencies for the variants within the cohort.

I found this plink approach but wondering if there is any other method or tool that can calculate frequencies directly using the VCF or GFF files?

GFF example

##gff-version 3
chr1    DRAGEN  CNV     925732  945653  3       .       .       Alt=DUP;LinearCopyRatio=1.23097;CopyNumber=3;Genotype=./1;Qual=3;Filter=cnvQual;Start=925731;Stop=945653;Length=19922;BinCount=30;ImproperPairsCount=8,7;color=#DDDDDD;
chr1    DRAGEN  CNV     1468885 1478297 11      .       .       Alt=DEL;LinearCopyRatio=0.677751;CopyNumber=1;Genotype=0/1;Qual=11;Filter=cnvQual;Start=1468884;Stop=1478297;Length=9413;BinCount=4;ImproperPairsCount=1,10;color=#DDDDDD;
chr1    DRAGEN  CNV     2073665 2073797 52      .       .       Alt=DEL;LinearCopyRatio=8.51417e-10;CopyNumber=0;Genotype=1/1;Qual=52;Filter=PASS;Start=2073664;Stop=2073797;Length=133;BinCount=1;ImproperPairsCount=0,0;color=#0000FF;
chr1    DRAGEN  CNV     2321254 2336850 51      .       .       Alt=DUP;LinearCopyRatio=1.43867;CopyNumber=3;Genotype=.1;Qual=51;Filter=PASS;Start=2321253;Stop=2336850;Length=15597;BinCount=8;ImproperPairsCount=4,4;color=#FF0000;
chr1    DRAGEN  CNV     5952701 5986327 4       .       .       Alt=DUP;LinearCopyRatio=1.23552;CopyNumber=3;Genotype=.1;Qual=4;Filter=cnvQual;Start=5952700;Stop=5986327;Length=33627;BinCount=12;ImproperPairsCount=32,8;color=#DDDDDD;

VCF example

#CHROM  POS     ID      REF     ALT     QUAL    FILTER  INFO    FORMAT  ID_001
chr1    925731  DRAGEN:GAIN:chr1:925732-945653  N       <DUP>   3       cnvQual SVLEN=19922;SVTYPE=CNV;END=945653;REFLEN=19922  GT:SM:CN:BC:PE  ./1:1.23097:3:30:8,7
chr1    1468884 DRAGEN:LOSS:chr1:1468885-1478297        N       <DEL>   11      cnvQual SVLEN=-9413;SVTYPE=CNV;END=1478297;REFLEN=9413  GT:SM:CN:BC:PE  0/1:0.677751:1:4:1,10
chr1    2073664 DRAGEN:LOSS:chr1:2073665-2073797        N       <DEL>   52      PASS    SVLEN=-133;SVTYPE=CNV;END=2073797;REFLEN=133    GT:SM:CN:BC:PE  1/1:8.51417e-10:0:1:0,0
chr1    2321253 DRAGEN:GAIN:chr1:2321254-2336850        N       <DUP>   51      PASS    SVLEN=15597;SVTYPE=CNV;END=2336850;REFLEN=15597 GT:SM:CN:BC:PE  ./1:1.43867:3:8:4,4
cnv vcf variant frequency
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written by barslmn • barslmn

2 answers

If you use the multisample CNV caller from DRAGEN, you'll be able to calculate AC/AF/AN directly in the VCF, as copy numbers will be jointly segmented across samples. As it is, you should find that a small fraction of the variants exactly match, as the breakpoints will be ragged. As such you're probably best off with gff -> bed -> bedtools multiinter (or other interval arithmetic you choose) to establish "consensus" copy number events and a list of their carriers. Also dup/del need to be processed separately, with deletions retaining their genotypes (since one can me missing 1 or 2 copies).

Good luck!

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written by LChart LChart

Thanks for your directions. One thing I notice when I look back on documentation is that joint CNV calling examples are given as trios. That's why I didn't try to use the joint calling. I will give it shot and see if it works without the pedigree file.

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written by barslmn • barslmn

Looks like this question got a lot of views. Here is my follow-up on this.

This is the script I come up with in order to process the data from seg files. I have tryed it only with DRAGEN output, so YMMV based on your input. We are using multiinter here to calculate occurences of CNVs and tagging them by their length, we are then using bedtools intersect to annotate our occurence data back to CNVs. Lastly we are using ClassifyCNV for the ACMG classification. All the bed files and tables are visualized with the IGV and tabulator. HTML file and other result files are then served over using a local server like: python -m http.server 8080. Its kinda home brew solution right now but if anyone is interested maybe I can elaborate on it.

Resulting report looks like this: enter image description here

Here are some of the visual guide for the script: enter image description here enter image description here bedtools multiinter enter image description here enter image description here bedtools intersect

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written by barslmn • barslmn

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