What is Varapp ?¶
Varapp is an application to filter genetic variants, with a reactive graphical user interface.
The application has been developed in a collaboration between the Swiss Institute of Bioinformatics (SIB) and the Lausanne University hospital (CHUV).
Although it can be used as a desktop app, it is meant to be deployed as a web service for a research group.
Common filtering pipelines can be very tedious, including an annotation step, complicated forms, multiple exports to spreadsheets, merging and manual curation of theses spreadsheets. Although there already exist several tools to facilitate the annotation of lists of variants and apply basic filters such as frequency in a population, quality or location, Varapp has at least one of the following advantages over existing software:
- Security: It does not require to upload data to a cloud or external client; one can deploy the app on any local computer and keep the data private.
- Fast, non-trivial filtering based on family pedigree, including complex cases such as compound heterozygous, in less than a second for 500K variants.
- Reproducibility: It uses a relational database, adding the potential to cross information between experiments, reuse the results of previously studied data, and keep track of the annotation/versions used to produce the results.
- Reactive user interface: Apply a filter and see the result immediately.
- Easy sharing of the results: send a URL to a colleague, and he sees the current state of your analysis just as you do.
Varapp is typically well-suited to cover the following two use cases, the result of which is obtained within a few seconds:
We consider all variants of one family and search for the variants that are susceptible to cause an hereditary disease. Varapp provides one-click filters for dominant, recessive, de novo, X-linked, and compound heterozygous cases.
We consider the same few genes (typically a few hundred) in a large series of independent individuals. We seek rare variants with strong impact, then inspect the individual(s) that carry them.
Varapp is not...¶
a variants caller:
It starts after the variant calling, and uses multi-sample VCF files generated by variant callers (e.g. GATK).
a variants annotation tool:
adapted to whole genome sequencing, or to thousands of samples:
For the moment, the app is responsive with datasets up to 500‘000 variants and a few hundred individuals. Performance issues are expected with larger datasets. For exome sequencing on large cohorts, we recommend to split the dataset in batches of 100-200 samples.
How can I try it?¶
One public, demo version of the program is available at https://varapp-demo.vital-it.ch .
This version runs or minimal hardware, thus its performance is not comparable to a real production setup.
Log in as user “demo” with password “demo”. You will be granted access to a variants database “demo”. Try the following standard filters:
- Recessive scenario
- 1% frequencies in 1000 Genomes, ESP and EXAC
- Quality filter: PASS (VQSR)
- HIGH/MED impact
You should retreive a single variant on gene TBC1D7 that has been published in Hum Mutat. 2014 Apr;35(4):447-51.
Prior to making it public, this dataset has been anonymized and obfuscated. Parents variant data was generated by random shuffling variants from several independent exome datasets. Children variant data was derived from the shuffled parents data. The TBC1D7 pathogenic variant was then added following recessive pattern of inheritance.
A second, public dataset “hapmap” of 170K variants is available (source: HapMap). Switch to it using the database selection button in the top right corner. Try double-clicking a variant to view the read alignment that is at the origin of the call. (To save disk space, only alignments on the first 3M bp of chromosome 1 are available).
If you liked it, we encourage you to deploy an instance at your own lab and share the experience.
Please add this reference to your publication if Varapp helped you in your research: http://biorxiv.org/content/early/2016/06/27/060806.
The source code is available in Github. Bug reports, suggestions, contributions and comments are all welcome.
These are the new features that we are either working on now or would like to add progressively to the program.
- Get rid of VEP for the annotation.
- View local alignments in a viewer similar to IGV.
- Easy installer.
- Scale up to full genome.
- More flexibility with the annotation.
- Calculate variants frequencies across several databases of one user/group.