system_genetics/rnaseq/step3_align/snippet.sh

#!/bin/bash
#
# Align reads against reference genome.

STORAGE="/groups/umcg-griac/tmp04/rawdata/$(whoami)/step3"
# Store genome index in this location:.
GENOME_INDEX="${STORAGE}/genome_index"
mkdir -p "${GENOME_INDEX}"
# Store the generated `Aligned.sortedByCoord.out.bam` in this dir.
ALIGNMENT_OUTPUT="${STORAGE}/alignment"
mkdir -p "${ALIGNMENT_OUTPUT}"

# 1) Generate genome index.
#
# N.B.:
# - We're assuming a read size of 100 bp (--sjdbOverhang 100). Refer back to the
#   previous quality control steps if you are unsure about the size. In case of
#   reads of varying length, the ideal value is max(ReadLength)-1.
# - We're using gzip compressed reference data (--readFilesCommand zcat), i.e.,
#   .gtf.gz and fa.gz. If not, you can remove the `zcat` flag.

# Storage location reference data (in this case on calculon).
REFERENCE_DATA="/groups/umcg-griac/prm02/rawdata/reference/genome"
GTF_FILE="${REFERENCE_DATA}/Homo_sapiens.GRCh38.100.gtf.gz"
FASTA_FILE="${REFERENCE_DATA}/Homo_sapiens.GRCh38.dna.primary_assembly.fa.gz"

STAR \
    --runThreadN 8 \
    --runMode genomeGenerate \
    --readFilesCommand zcat \
    --sjdbOverhang 100 \
    --genomeFastaFiles ${FASTA_FILE} \
    --sjdbGTFfile ${GTF_FILE} \
    --genomeDir ${GENOME_INDEX}


# 2) Do the actual alignment.
#
# N.B.:
# - We are assuming paired-end, gzip compressed (--readFilesCommand zcat)  FastQ
#   files.

# THe compressed paired-end FastQ's that we are aligning.
R1="sample1_R1.fastq.gz"
R2="sample1_R2.fastq.gz"

STAR \
    --runThreadN 8 \
    --readFilesCommand zcat \
    --readFilesIn "${R1}" "${R2}" \
    --outSAMtype BAM SortedByCoordinate \
    --genomeDir ${GENOME_INDEX} \
    --outFileNamePrefix "${ALIGNMENT_OUTPUT}"