snp-search¶ ↑
an easy to use tool for management of SNPs generated from haploid next generation sequencing data. Given a vcf file, snp-search stores the SNPs generated by the variant calling algorithm into a sqlite database. snp-search can then be used to extract useful information from the database.
Obtaining and installing the code¶ ↑
SNPsearch is written in Ruby and operates in a Unix environment. It is made available as a gem. See the github site for more information (github.com/hpa-bioinformatics/snp-search).
To install snp-search, do
gem install snp-search
Requirements¶ ↑
Not much, you just need:
-
Unix. Once snp-search is installed, all the necessary gems to run snp-search will also be installed from Rubygems (note that Rubygems requires admin privileges. If you do not have admin privileges then we suggest you install RVM: (beginrescueend.com/rvm/install/) and then gem install snp-search).
-
ruby version 1.8.7 and above.
-
Optional: FastTree 2. If you require a tree output in Newick format, you must install FastTree from www.microbesonline.org/fasttree/#Install.
Thats it!
Running snp-search ¶ ↑
1- The first thing you need to do is to create the database (snp-search -create)
Two files are needed to create the SQLite3 database: 1A- Variant Call Format (.vcf) file (which contains the SNP information) 1B- Your database reference genome that you used to generate your .vcf file (in genbank or embl format, the script will automatically detect the format). You need the following parameters: -d Name of your database (note that this is a required field in all commands). -v .vcf file -r Database Reference genome (The same file that was used in generating the .vcf file). This should be in genbank or embl format. Optional: -A AD ratio cutoff (default 0.9) Usage: snp-search -create -d my_snp_db.sqlite3 -r my_ref.gbk -v my_vcf_file.vcf Note: The strain names in your database will be taken from your vcf file so make sure they are named appropriately in your vcf file.
2- Now that you have created the database (my_snp_db.sqlite3) you can use snp-search to output several queried data.
First, you need to tell snp-search what you want out. You have several options:
- Querying the Database to select the number of unique SNPs within the list of the strains/samples provided (list_of_my_strains.txt). The output is a text file with a list of the unique SNPs and information about each SNP (e.g. if its synonymous or non-synonymous SNP).
-output -unique_snps -d db.sqlite3 [options]
-u, --unique_snps Query for unique snps in the database
-c, --cuttoff_snp_qual SNP quality cutoff, (default = 90)
-g, --cuttoff_genotype Genotype quality cutoff (default = 30)
-s, --strain The strains/samples you like to query (only used with -unique_snps flag)
-o, --out Name of output file, Required
Usage:
snp-search -O -u -d my_snp_db.sqlite3 -s list_of_my_strains.txt -o unique_snps.out
- Querying the database to output all SNPs without SNPs in a specified features in the database (e.g. phages). This is a way of ignoring SNPs in genes (likely to be mobile element genes) that are not needed for SNP analysis. The user has the option of generating a core SNP tree Newick file for SNP phylogeny (if -F option was used to ouput fasta file).
-output -all_or_filtered_snps -d db.sqlite3 [options]
-f, --all_or_filtered_snps SNPs from specified features in the database (if you do not want to ignore any SNPs, just use this option with -n -F/T -o)
-F, --fasta output fasta file format (default)
-T, --tabular output tabular file format
-c, --cuttoff_snp_qual SNP quality cutoff, (default = 90)
-g, --cuttoff_genotype Genotype quality cutoff (default = 30)
-R, --remove_non_informative_snps Only output informative SNPs. Only used with -e option
-e, --ignore_snps_in_range A list of position ranges to ignore e.g 10..500,2000..2500. Only used with -e option
-a, --ignore_strains A list of strains to ignore (seperate by comma e.g. S1,S4,S8 ). Only used with -f option
-I, --ignore_snps_on_annotation The name of the feature(s) to ignore. Features should be seperated by comma (e.g. phages,inserstion,transposons)
-o, --out Name of output file, Required
-t, --tree Generate SNP phylogeny (only used with -fasta option)
-p, --fasttree_path Full path to the FastTree tool (e.g. /usr/local/bin/FastTree. only used with -tree option)
Usage:
snp-search -O -F -f -n my_snp_db.sqlite3 -a phage,insertion,transposon -R -o snps_without_phages.fasta
- Optionally, you can add the following options to generate a phylogenetic tree from the resulting fasta file:
-t Generate SNP phylogeny
-p Full path to the FastTree tool (e.g. /usr/local/bin/FastTree. only used with -tree option)
Usage:
snp-search -O -F -e -n my_snp_db.sqlite3 -a phage,insertion,transposon -r -t -p /usr/local/bin/FastTree -o snps_without_phages.fasta
The algorithm FastTree is used to generate the nwk file. FastTree can be downloaded from http://www.microbesonline.org/fasttree/#Install (see above)
- Output all SNPs with information. Information for each SNP includes whether the SNP is synonymous or non-synonymous, gene function, whether it is a pseudogene and other useful information. These information will be tab-seperated.
-output -info -d db.sqlite3 [options]
-i, --info Output various information about SNPs
-c, --cuttoff_snp_qual SNP quality cutoff, (default = 90)
-g, --cuttoff_genotype Genotype quality cutoff (default = 30)
-o, --out Name of output file, Required
Usage:
snp-search -O -info -d my_snp_db.sqlite3 -o snps_all_with_info.txt
View database in Unix or in a GUI ¶ ↑
Your database will be in sqlite3 format. If you like to view your table(s) and perform direct queries you can type
sqlite3 snp_db.sqlite3
Alternatively, you may download a SQL tool to view your database (e.g. SQLite sorcerer).
Contact¶ ↑
If you have any comments, questions or suggestions, please email
ali.al-shahib@phe.gov.uk
or
anthony.underwood@phe.gov.uk
Have fun snp-searching!
Copyright¶ ↑
Copyright © 2012 Ali Al-Shahib. See LICENSE.txt for further details.