Bio Variant Calling Deepvariant

Version Compatibility

Reference examples tested with: DeepVariant 1.6.1+, GLnexus 1.4+, bcftools 1.19+

Before using code patterns, verify installed versions match. If versions differ:

• CLI: docker run google/deepvariant:<tag> /opt/deepvariant/bin/run_deepvariant --helpfull | head to confirm flags and available --model_type tokens for the build
• bcftools --version and bcftools --help to confirm flags

If code throws errors, introspect the installed container and adapt the example to match the actual API rather than retrying.

Note: newer DeepVariant releases (1.8.x+) add model types and rename image tags; always confirm the --model_type tokens against the exact container in use rather than assuming this list is complete.

DeepVariant Variant Calling

"Call germline variants with DeepVariant" -> Render each candidate site's read pileup as a multi-channel image and classify its genotype with a trained CNN.

• CLI: run_deepvariant (one-shot) or make_examples -> call_variants -> postprocess_variants (three-stage), shipped as a Docker/Singularity container

The governing principle

DeepVariant replaces the parametric HMM/Bayesian genotyper with a trained convolutional neural network that classifies pileup images into hom-ref / het / hom-alt. Two consequences drive every downstream decision:

1. There is NO hand-tuned statistical filter to apply afterward. The CNN already emits a calibrated FILTER column (PASS for confident variants, RefCall for sites judged homozygous reference). Applying GATK hard filters (QD/FS/MQ/SOR thresholds) or VQSR on top of DeepVariant output removes true positives, not false ones -- those annotations do not even exist in the VCF. Post-call handling is limited to QUAL/GQ thresholding, normalization, and region restriction.
2. The network learned its error model from RAW base qualities, so running BQSR upstream costs runtime and slightly LOWERS DeepVariant accuracy. DeepVariant's own guidance is to skip BQSR. The input requirement is a sorted, indexed, duplicate-marked BAM/CRAM -- nothing more.

DeepVariant calls germline variants only. For somatic calling use DeepSomatic (a separate tool from the same team); the diploid genotype classes cannot represent subclonal allele fractions.

How DeepVariant Works

Three stages, run together by run_deepvariant or separately for control over intermediates:

1. make_examples (CPU-bound, the runtime bottleneck) scans the BAM for candidate sites where non-reference support passes a permissive recall-tuned screen, then renders each candidate as a multi-channel pileup image written to sharded TFRecords. Rows are reads, columns are reference positions; channels encode read base identity, base quality, mapping quality, strand, whether the read supports the candidate allele, and whether the base differs from the reference. Illumina models add an insert-size channel; long-read models add a haplotype channel. Exact tensor dimensions are version-dependent -- treat any published figure as illustrative. Parallelized by --num_shards.
2. call_variants runs the trained Inception-family CNN over each example and emits a 3-class genotype-likelihood output. This is the only GPU-accelerable stage.
3. postprocess_variants sorts CNN outputs, resolves multiallelics, and converts likelihoods to VCF/gVCF.

This image-based design is why DeepVariant beats parametric callers on indels and in difficult contexts (homopolymers, tandem repeats, low-complexity regions): the CNN learns visual patterns in pileup geometry that heuristic filters miss. Models are platform-specific because sequencer error modes (Illumina substitutions, ONT homopolymer indels) are visually different and each model learns the artifact distribution of its training platform.

Model Selection

--model_type is load-bearing: using the wrong model silently degrades accuracy because the CNN expects platform-specific error patterns in the pileup and does NOT error out. Match the model to the instrument that produced the reads, not to the analysis goal.

When to Use DeepVariant vs GATK vs DRAGEN

• DeepVariant -- best indel accuracy and best difficult-region/long-read performance among open tools; generalizes across platforms with a model swap; needs no filter tuning. Default choice for indels, difficult regions, and long reads.
• GATK HaplotypeCaller -- every parameter auditable, mature joint calling with reference-confidence squaring-off, and regulatory precedent. Prefer for very large cohorts needing GenomicsDB scaling or clinical pipelines already validated on GATK. See variant-calling/gatk-variant-calling.
• DRAGEN -- FPGA-accelerated, ~20-25 min per 30x genome, wins the difficult-to-map benchmarks; prefer for throughput when the hardware or cloud is available (subject to the GIAB-overfitting caveat below).

The full engine-selection decision table lives in variant-calling/variant-calling -- consult it before committing a production pipeline; the choice depends on cohort size, platform, auditability, and throughput, not on accuracy alone.

Installation

docker pull google/deepvariant:1.6.1

# GPU support (NVIDIA GPU + nvidia-container-toolkit required)
docker pull google/deepvariant:1.6.1-gpu

# Singularity alternative
singularity pull docker://google/deepvariant:1.6.1

One-Shot Run

docker run -v "${PWD}:/input" -v "${PWD}/output:/output" \
    google/deepvariant:1.6.1 \
    /opt/deepvariant/bin/run_deepvariant \
    --model_type=WGS \
    --ref=/input/reference.fa \
    --reads=/input/sample.bam \
    --output_vcf=/output/sample.vcf.gz \
    --output_gvcf=/output/sample.g.vcf.gz \
    --num_shards=16

Always generate a gVCF (--output_gvcf) even for a single sample -- it enables downstream joint calling with GLnexus without re-running DeepVariant.

Exome/targeted calling adds --regions:

docker run -v "${PWD}:/data" google/deepvariant:1.6.1 \
    /opt/deepvariant/bin/run_deepvariant \
    --model_type=WES \
    --ref=/data/reference.fa \
    --reads=/data/exome.bam \
    --regions=/data/targets.bed \
    --output_vcf=/data/exome.vcf.gz \
    --num_shards=8

PacBio HiFi and ONT differ only in --model_type=PACBIO or --model_type=ONT_R104. HiFi's Q30+ reads give the CNN clean pileups; R10.4+ chemistry substantially reduces the systematic homopolymer-indel errors that made earlier ONT chemistries unusable for short-variant calling.

Three-Stage Pipeline

For control over intermediates (custom sharding, resuming, mixing CPU/GPU nodes), run the stages separately:

# Stage 1: render pileup images (CPU-bound; parallelize with sharded --examples)
docker run -v "${PWD}:/data" google/deepvariant:1.6.1 \
    /opt/deepvariant/bin/make_examples \
    --mode calling \
    --ref /data/reference.fa \
    --reads /data/sample.bam \
    --examples /data/examples.tfrecord.gz \
    --gvcf /data/gvcf.tfrecord.gz

# Stage 2: CNN inference (the GPU-accelerable stage)
docker run -v "${PWD}:/data" google/deepvariant:1.6.1 \
    /opt/deepvariant/bin/call_variants \
    --outfile /data/call_variants.tfrecord.gz \
    --examples /data/examples.tfrecord.gz \
    --checkpoint /opt/models/wgs

# Stage 3: emit VCF/gVCF
docker run -v "${PWD}:/data" google/deepvariant:1.6.1 \
    /opt/deepvariant/bin/postprocess_variants \
    --ref /data/reference.fa \
    --infile /data/call_variants.tfrecord.gz \
    --outfile /data/output.vcf.gz \
    --gvcf_outfile /data/output.g.vcf.gz \
    --nonvariant_site_tfrecord_path /data/gvcf.tfrecord.gz

GPU Acceleration

GPU acceleration benefits ONLY call_variants (CNN inference); make_examples and postprocess_variants are CPU-bound and scale with --num_shards. For large cohorts, parallelizing across samples on CPU nodes is often more cost-effective than queuing for GPUs.

docker run --gpus all -v "${PWD}:/data" \
    google/deepvariant:1.6.1-gpu \
    /opt/deepvariant/bin/run_deepvariant \
    --model_type=WGS \
    --ref=/data/reference.fa \
    --reads=/data/sample.bam \
    --output_vcf=/data/output.vcf.gz \
    --num_shards=16

DeepTrio (Family / Trio Calling)

DeepTrio extends the pileup image to span proband plus both parents simultaneously, so the CNN learns inheritance context and calls de-novo variants directly. This beats naive trio subtraction, whose apparent de-novo set is dominated by false positives from independent per-sample errors. Use DeepTrio for family studies, Mendelian-consistency work, and de-novo discovery. It ships proband and parent models for Illumina WGS/WES and PacBio (--model_type WGS|WES|PACBIO) and uses a separate image tag (deeptrio-<version>).

docker run -v "${PWD}:/data" google/deepvariant:deeptrio-1.6.1 \
    /opt/deepvariant/bin/run_deeptrio \
    --model_type=WGS \
    --ref=/data/reference.fa \
    --reads_child=/data/child.bam \
    --reads_parent1=/data/father.bam \
    --reads_parent2=/data/mother.bam \
    --sample_name_child=CHILD \
    --sample_name_parent1=FATHER \
    --sample_name_parent2=MOTHER \
    --output_vcf_child=/data/child.vcf.gz \
    --output_vcf_parent1=/data/father.vcf.gz \
    --output_vcf_parent2=/data/mother.vcf.gz \
    --output_gvcf_child=/data/child.g.vcf.gz \
    --output_gvcf_parent1=/data/father.g.vcf.gz \
    --output_gvcf_parent2=/data/mother.g.vcf.gz \
    --num_shards=16

Merge the three per-sample gVCFs with GLnexus (below) into one trio VCF; the joint context is what supports Mendelian-violation and de-novo-rate analysis.

Joint Calling with GLnexus

DeepVariant gVCFs are joint-genotyped with GLnexus, NOT GATK GenotypeGVCFs -- GLnexus performs allele unification across per-sample gVCFs and grows its database incrementally as samples are added, avoiding full-cohort reprocessing. See variant-calling/joint-calling for the GATK reference-confidence alternative and when each is appropriate.

for bam in *.bam; do
    sample=$(basename "$bam" .bam)
    docker run -v "${PWD}:/data" google/deepvariant:1.6.1 \
        /opt/deepvariant/bin/run_deepvariant \
        --model_type=WGS --ref=/data/reference.fa --reads=/data/$bam \
        --output_vcf=/data/${sample}.vcf.gz \
        --output_gvcf=/data/${sample}.g.vcf.gz \
        --num_shards=16
done

docker run -v "${PWD}:/data" quay.io/mlin/glnexus:v1.4.1 \
    /usr/local/bin/glnexus_cli \
    --config DeepVariantWGS \
    /data/*.g.vcf.gz \
    | bcftools view - -Oz -o cohort.vcf.gz

The DeepVariant+GLnexus path is a strong open-source alternative to GATK joint calling. Representative benchmark (Yun et al. 2020, GIAB, 40x WGS): cohort Mendelian-violation rate 1.7% vs GATK-VQSR 5.0%; SNP F1 error 0.07% vs 1.23%; indel F1 error 1.14% vs 2.92%. On a 2,504-sample cohort the GLnexus merge ran ~8x faster on chromosome 22 (0.84 h vs 6.83 h) and DeepVariant gVCFs were ~7x smaller on disk genome-wide (2.20 TB vs 15.16 TB). These figures are sample-, coverage-, and version-specific -- not fixed constants.

Output and Quality Control

DeepVariant output is already CNN-filtered (PASS / RefCall in FILTER). Do NOT apply GATK hard filters or VQSR. Legitimate post-call handling is QUAL/GQ thresholding, normalization, and region restriction.

bcftools stats output.vcf.gz > stats.txt

# Ti/Tv sanity check: expect ~2.0-2.1 for WGS, ~3.0-3.3 for WES
bcftools stats output.vcf.gz | grep TSTV

# QUAL is CNN confidence; GQ is genotype quality. Threshold, do not re-filter on GATK annotations.
bcftools view -i 'QUAL>20 && FMT/GQ>20' output.vcf.gz -Oz -o filtered.vcf.gz

Benchmarking and the GIAB Circularity Caveat

Benchmark against a GIAB truth set with a haplotype-aware comparator (hap.py + vcfeval), restricted to the confident-region BED and stratified by region difficulty:

docker run -v "${PWD}:/data" jmcdani20/hap.py:latest \
    /opt/hap.py/bin/hap.py \
    /data/HG002_GRCh38_truth.vcf.gz \
    /data/deepvariant_output.vcf.gz \
    -f /data/HG002_confident.bed \
    -r /data/reference.fa \
    -o /data/benchmark \
    --engine=vcfeval --threads 16

The load-bearing caveat: DeepVariant is TRAINED on GIAB truth sets (primarily HG001) and then routinely BENCHMARKED on GIAB samples. When train and test both derive from HG001-HG007, a headline F1 of 0.999 partly measures memorization of the truth set's idiosyncrasies, not generalization. The honest read weights held-out-sample performance (train on HG001/3/4/5/6/7, test on HG002 -- as precisionFDA V2 did by scoring the semi-blinded parents HG003/HG004), reports difficult-region and CMRG strata rather than one genome-wide number, and -- before clinical deployment -- validates on population-matched, characterized material rather than trusting a published GIAB F1. A benchmark that reports one global F1 without stratification and without a held-out or non-GIAB sample is not decision-grade (Krusche et al. 2019).

Approximate Accuracy vs Other Callers

Approximate F1 from GIAB HG002/HG003/HG004 on GRCh38; exact values vary by sample, coverage, and version. On easy SNPs every modern caller exceeds F1 0.999, so the decision-relevant gaps are indels and difficult regions.

Resource Requirements

Common Errors

Related Skills

• variant-calling/gatk-variant-calling - GATK HaplotypeCaller alternative with auditable parameters, joint calling, and VQSR/VETS
• variant-calling/variant-calling - engine-selection decision table (DeepVariant vs GATK vs DRAGEN vs bcftools) and lightweight bcftools calling
• variant-calling/joint-calling - GATK reference-confidence joint genotyping, the alternative to GLnexus for cohorts
• variant-calling/filtering-best-practices - post-calling filtering for callers that DO expose hard-filter annotations (not DeepVariant)
• variant-calling/vcf-statistics - QC metrics (Ti/Tv, het/hom) for the called VCF
• long-read-sequencing/clair3-variants - long-read variant-calling alternative, especially for ONT R9.4 and resource-constrained settings

References

• Poplin R, Chang P-C, Alexander D, et al. A universal SNP and small-indel variant caller using deep neural networks. Nature Biotechnology 36(10):983-987 (2018). DOI 10.1038/nbt.4235. (DeepVariant.)
• Yun T, Li H, Chang P-C, Lin MF, Carroll A, McLean CY. Accurate, scalable cohort variant calls using DeepVariant and GLnexus. Bioinformatics 36(24):5582-5589 (2020). DOI 10.1093/bioinformatics/btaa1081. (DeepVariant+GLnexus cohort benchmark.)
• Kolesnikov A, Goel S, Nattestad M, et al. DeepTrio: Variant Calling in Families Using Deep Learning. bioRxiv 2021.04.05.438434 (2021). DOI 10.1101/2021.04.05.438434. (Preprint; DeepTrio.)
• Shafin K, Pesout T, Chang P-C, et al. Haplotype-aware variant calling with PEPPER-Margin-DeepVariant enables high accuracy in nanopore long-reads. Nature Methods 18:1322-1332 (2021). DOI 10.1038/s41592-021-01299-w. (ONT long-read path.)
• Krusche P, Trigg L, Boutros PC, et al. Best practices for benchmarking germline small-variant calls in human genomes. Nature Biotechnology 37:555-560 (2019). DOI 10.1038/s41587-019-0054-x. (hap.py/vcfeval, confident regions, stratification.)
• Olson ND, Wagner J, McDaniel J, et al. PrecisionFDA Truth Challenge V2: Calling variants from short and long reads in difficult-to-map regions. Cell Genomics 2(5):100129 (2022). DOI 10.1016/j.xgen.2022.100129. (Held-out scoring; difficult-region performance.)