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ga4gh.org

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GKS: the Fellowship of the VRS

Andreas Prlic & Larry Babb (and Alex Wagner)

ga4gh.org

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Agenda (draft)

  • Review VRS 1.3 work, Maturity Model, Lessons Learned
  • Main Event: VRS 2.0 alpha: Key Changes (review & discuss)
    • No more ValueObjectDescriptors!
    • New! SequenceReference Class
    • New! ReferenceLengthExpression State
    • Re-thinking how we handle non-identifiable Variants.
    • SV SIG & expectations for 2.0 - Impacts on Haplo/Genotypes
    • Categorical Variation study group plans
  • ClinVar & CIViC GK-Pilot v2 alpha introduction - prep for next session!

ga4gh.org

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VRS Greatest Hits

Notable Features

Ref. Allele Guidance

Gen. Normalization

Release Cycle

VMC

1.0

Notable Classes

Allele

Text Variation

SequenceLocation

SequenceState

SimpleInterval

Notable Features

Terminology

Information Model

Schema

VOCA Normalize

VRS-Python

Notable Features

Systemic Variation

Molecular Variation

Primitive Constraints

GA4GH Domain Docs

1.1

1.2

October 2019

September 2020

July 2021

May 2016

VR

October 2017

GKS and the Variation Representation Team is announced at the 5th GA4GH Plenary

The Variant Model Collaboration is formed to model Variation as semantically-linked value objects

1.3

Notable Classes

ChromosomeLocation

CytobandInterval

Haplotype

VariationSet

Notable Classes

SequenceExpressions

Gene (&Features)

CopyNumber

April 2023

Notable Classes

Genotype

CopyNumberCount

CopyNumberChange

Notable Features

PGx Diplotype

Improved CNVs

ga4gh.org

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VRS: a Genomic Knowledge Standard

Copy Number Count

Copy Number Change

Genotype

Pugh T, et al. Genetics in Medicine (2015)

Goar W, et al. Pacific Symposium On Biocomputing (2023)

ga4gh.org

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VRS v1.3 at scale: gnomAD

Added VRS for all 759.3 million variants in gnomAD v3 Hail Tables, plus reference alleles.�Over 1.5 billion VRS v1.3 Alleles, now searchable by range and computed identifier.

ga4gh.org

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Contextualizing evidence with VRS: MaveDB

Arbesfeld J, et al. bioRxiv (2023)

  • MAVE Libraries describe variants on assay seqs�
  • Homology mapping provides a means of linking variants from assay to human reference�
  • VRS provides a vocab for variants on custom and common sequences

ga4gh.org

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Contextualizing evidence with VRS: MaveDB

ga4gh.org

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A Glimpse of the Future: GK-Pilot v2

2022 GA4GH 10th Plenary: Genomic Knowledge Pilot (GK-Pilot) v1

Recap

  • Version 1 pilot of the ClinVar, CIViC, and MOA genomic knowledgebases�
  • Built on VRS v1.2�
  • Used VRSATILE Value Object Descriptors�
  • Used to trial GKS spec usage for genomic knowledge sharing

ga4gh.org

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A Glimpse of the Future: GK-Pilot v2

GK-Pilot v2 Enhancements

Uses VRS 2.0-alpha

  • VRS 2.0-alpha enables more compact and self-descriptive variant representation than v1�
  • IRI support allows for implementation-specific references in complex objects; no ambiguity!��

Uses Categorical Variation

  • Alpha model for categorical variation provides semantic precision and with a domain model built for genomic knowledge search

Extends the VA Statement model

  • Statements inherit Subject, Predicate, Object, Qualifier fields for computability
  • Field names maintain readability for ease of implementation
  • No more propositions: all objects follow the same self-descriptive VRS 2.0-alpha architecture

ga4gh.org

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Maturity Model Today

Level

Criteria

Schema Changes

Support

Alpha

A requirements survey has been done and an information model (IM) drafted. The IM has been realized as a technical schema.

Expected frequently. Not permitted in pre-release / release branches.

IM and technical schema are produced and made publicly available.

Beta

Alpha + the technical schema has been used to generate messages in a test system, and a validation framework applied to ensure specification conformance. Documentation has been generated and is publicly accessible.

Expected infrequently. Only permitted in beta release branches. Notifications sent to the GKS VR team.

Alpha + test system data, validation framework, and documentation are made publicly available.

Release Candidate

Beta + the data class is sufficient for multiple data providers. Inter-system interoperability has been demonstrated. Data class is considered ready for broad adoption and testing.

Expected rarely. Only permitted in beta and release candidate branches. Changes in consultation with registered adopters.

Beta + reference implementation tools are published

Stable

Release Candidate + Data class has been sufficiently tested to warrant long-term support from the specification maintainers.

Breaking changes will not occur within any branch of a major version once stable.

Release Candidate + major version minted. The data class will be fully supported by all spec maintainer tools until 2 years following the next major version release.

ga4gh.org

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Repo Branch Structure and Data Class Maturity

Feature Branches

(Alpha Maturity)

Pre-Release Branches

(Beta / RC Maturity)

Release Branches

(Stable Maturity)

ga4gh.org

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Main Event: VRS 2.0 alpha: Key Changes (focused discussions)

ga4gh.org

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VRS 2a: No more ValueObjectDescriptors!

Optional fields allowed on VRS objects

Modified "Digest" algorithm to understand "required" attributes

Every object has an optional "digest" attribute

The right attribute in the right place (for nested and referenced objects)

ga4gh.org

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Resource identifiers (no more CURIE?)

Identified need for more direct method for referenceable objects in json

Investigated FHIRs solution

Proposing use of JSON schema uri/iri-reference for Resource identifiers

ga4gh.org

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VRS 2a: New! SequenceReference Class

This is the "special" bridge to coordinating with the RefGet SQ id

To represent Sequences in VRS we need to use SQ.<digest>

We also need the control to decorate and reference the Sequence

SQR is our solution

ga4gh.org

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VRS 2a: New! ReferenceLengthExpression State

ga4gh.org

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VRS 2a: Re-thinking (non-identifiable) Text Variants

The Utility Variation concepts in VRS 1.x

VariationSet

Text

To our knowledge these have not materialized to be useful

Text Variation is nonsense as an identifiable VRS variation

But we need to handle situations these use cases

DescribedVariation is a CategoricalVariation concept to replace Text.

ga4gh.org

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SV SIG & Categorical Variation Plans

Active Initiative: � Structural Variation

Upcoming Initiative: � Categorical Variation

ga4gh.org

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Categorical Variation

Categorical variant

  • A set of assayed variants defined by shared theoretical properties and biological constraints
  • Abstractions over assayed variants and associated evidence items
  • Very important to research groups

Examples:

  • Genome Sequence Variants
  • BRAF V600E variants
  • Copy Number Variants
  • Gene Fusions, etc...

ga4gh.org

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Categorical Variation - Problem

  1. CV ontology and hierarchy not well understood
  2. CVs arise spontaneously and organically from research programs
  3. Important for connecting assays to evidence
    1. ENST00000288602.6:c.1799TG>AA
    2. Lots of literature on BRAF V600E variants, maybe not that one specifically.

Want to better support this in future. (VRS, MetaKB, etc)

ga4gh.org

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Categorical Variation

ga4gh.org

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Categorical Variation - Typology in CIViC

ga4gh.org

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ClinVar & CIViC GK-Pilot v2 alpha Introduction

prep for next session!

ga4gh.org

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ClinVar GK-Pilot Statement Walkthrough

ga4gh.org