SeqShop: Estimates of Genetic Ancestry Practical, June 2014

Introduction

See the tutorial slides for an introduction of the LASER analysis workflow, input/output file formats, and usage of the LASER software.

The main purpose of this page is to provide step-by-step command lines for estimating ancestry of 6 targeted sequencing samples (2 HapMap trios) in a principal component space generated using genome-wide SNP data from the Human Genome Diversity Project (HGDP).

LASER workflow

LASER workflow

Getting started

Create a working directory:

mkdir ancestry
cd ancestry

Download and decompress software package:

wget http://www.sph.umich.edu/csg/chaolong/LASER/LASER-2.01.tar.gz
tar xzvf LASER-2.01.tar.gz

Set up to access data:

source /home/chaolong/LASER-Tutorial/setup.txt

What is in the setup.txt file:

export GC=/home/mktrost/seqshop/gotcloud
export BAM=/home/chaolong/LASER-Tutorial/BAM
export REF=/home/chaolong/LASER-Tutorial/reference
export HGDP=/home/chaolong/LASER-Tutorial/HGDP

Preparing input files for LASER

Step 0: vcf --> geno

This step prepares the reference panel by converting a VCF genotype file to a GENO file. We will skip this step and use a ready-to-use HGDP reference panel. A typical command to run the vcf2geno tool is given in the file "./LASER-2.01/vcf2geno/cmd.sh".

Step 1: bam --> pileup

This step uses samtools to generate pileup files from bam files. Please only try one sample so that we won't overload the sever with everyone running 6 jobs at the same time. Pileup files for these 6 samples have been prepared for later steps. It takes about 2 mins for each pileup job.

$GC/bin/samtools mpileup -q 30 -Q 20 -f ./reference/hs37d5.fa.rz -l ./HGDP/HGDP_938.bed ./BAM/121101035.recal.bam > 121101035.recal.pileup &
# $GC/bin/samtools mpileup -q 30 -Q 20 -f ./reference/hs37d5.fa.rz -l ./HGDP/HGDP_938.bed ./BAM/121101043.recal.bam > 121101043.recal.pileup & 
# $GC/bin/samtools mpileup -q 30 -Q 20 -f ./reference/hs37d5.fa.rz -l ./HGDP/HGDP_938.bed ./BAM/121101050.recal.bam > 121101050.recal.pileup &
# $GC/bin/samtools mpileup -q 30 -Q 20 -f ./reference/hs37d5.fa.rz -l ./HGDP/HGDP_938.bed ./BAM/121101052.recal.bam > 121101052.recal.pileup &
# $GC/bin/samtools mpileup -q 30 -Q 20 -f ./reference/hs37d5.fa.rz -l ./HGDP/HGDP_938.bed ./BAM/121101415.recal.bam > 121101415.recal.pileup &
# $GC/bin/samtools mpileup -q 30 -Q 20 -f ./reference/hs37d5.fa.rz -l ./HGDP/HGDP_938.bed ./BAM/121101861.recal.bam > 121101861.recal.pileup &

Step 2: pileup --> seq

This step will generate a file called "hapmap_trios.seq", containing the information of 6 samples. It takes about 30 seconds to run. We used the pre-generated pileup files in the $BAM folder.

python ./LASER-2.01/pileup2seq/pileup2seq.py \
-m $HGDP/HGDP_938.site \
-b $BAM/AMD_roi_1-based.bed \
-i $BAM/AMD_hapmap_trios_id.txt \
-o hapmap_trios \
$BAM/121101035.recal.pileup \
$BAM/121101043.recal.pileup \
$BAM/121101050.recal.pileup \
$BAM/121101052.recal.pileup \
$BAM/121101415.recal.pileup \
$BAM/121101861.recal.pileup &

In the above command, -i specifies alternative IDs for the BAM files to be used in the .seq file (including popID and indivID). -b and -i are optional.