Is RB1 p.Arg556Pro (c.1667G>C) pathogenic?

RB1 p.Arg556Pro (c.1667G>C) is classified Uncertain significance in RB1 (ClinVar, Single submitter, 1 submitter; last evaluated 2025-05-05). AlphaMissense: likely pathogenic (0.9701); Absent from gnomAD v4.1; Associated with retinoblastoma.

What condition is associated with RB1 p.Arg556Pro (c.1667G>C)?

RB1 p.Arg556Pro (c.1667G>C) is associated with retinoblastoma (ClinVar).

How common is RB1 p.Arg556Pro (c.1667G>C) in the general population?

RB1 p.Arg556Pro (c.1667G>C) is absent from gnomAD v4.1 (gnomAD).

How is Retinoblastoma inherited?

Typically Autosomal dominant, Not applicable (Orphanet). A genetic counselor can assess individual risk for a family.

What do computational predictors say about RB1 p.Arg556Pro (c.1667G>C)?

AlphaMissense predicts likely pathogenic (score 0.9701) — an in-silico prediction, not a clinical call.

RB1 p.Arg556Pro

c.1667G>C · VCV3663564

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely pathogenic

0.9701 · ACMG-weighted

gnomAD v4.1

Absent

absent from gnomAD v4.1

Missense predictors

3/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

retinoblastoma

Computational evidence

Protein change
AlphaMissense	0.9701	likely pathogenic · top 8% in RB1
REVEL	0.689	pathogenic-leaning
SaProt	LLR -12.61	damaging
⇒ AlphaMissense, REVEL and SaProt all call this damaging.
Splicing
SpliceAI	<0.2	no splice effect predicted · four deltas, not one · how we know
Constraint at this position
Conservation	phyloP 8.6	GERP 1.6, phastCons 1
Regional constraint	o/e 0.81	unconstrained · MANE · 156 kb · p 9.1e-08 · regional, not allelic
Overall
CADD	26.5	PHRED · no single calibrated threshold — expert panels disagree

ClinVar classifies this uncertain; the computational predictors unanimously lean damaging — a triage signal, not a reclassification

AlphaMissense carries the ACMG weight for missense; REVEL and SaProt are independent agreement signals.

Population frequency

gnomAD v4.1 · exomes + genomes

Absent from gnomAD v4.1. Not observed in any sequenced alleles — a rarity signal (ACMG PM2-supporting), not evidence of pathogenicity on its own.

Variant & gene context

Gene: RB1
Protein: p.Arg556Pro
Coding: c.1667G>C
MANE Select: NM_000321
Type: single nucleotide variant
Location: chr13:48381415 (GRCh38)
Gene constraint: LOEUF 0.239 · pLI 1.00 · ClinGen HI 3/3 (gnomAD)
Structure: AlphaFold pLDDT 77.03 · 19 PDB
Residue 556: an α-helix; the 'pocket; binds t and e1a' region; the 'domain a' region

Full RB1 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

retinoblastoma — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Retinoblastoma (Orphanet):

Inheritance: Autosomal dominant, Not applicable
Onset: Antenatal, Childhood, Infancy
Prevalence: <1 / 1 000 000 (Europe)

Similar variants

RB1 p.Arg556Ter Pathogenic ★★ same residue
RB1 p.Arg556Leu Uncertain significance ★★ ⚠ same residue
RB1 p.Arg556Gln Conflicting classifications of pathogenicity ★ ⚠ same residue
RB1 p.Arg556Gly Uncertain significance ★ ⚠ same residue
RB1 p.Arg556= Likely benign ★ same residue
RB1 c.1049+1G>A Pathogenic/Likely pathogenic ★★ same condition
RB1 c.1049+1G>T Pathogenic/Likely pathogenic ★★ same condition
RB1 c.1049+3A>G Pathogenic/Likely pathogenic ★★ same condition

Built on 18 open, versioned datasets — ClinVar, gnomAD, AlphaMissense, REVEL, ClinGen & more — plus Sugi Variant's own cross-source analysis. Source data 2026-01–2026-10, ClinVar 2026-10. Full sources & versions →

Cite Sugi Variant

Gür T. Sugi Variant: A Deterministic Per-Variant Germline Reference from a Knowledge Graph for Humans and AI Agents. 2026. doi:10.5281/zenodo.21509445. This variant: https://sugi.bio/variant/rb1-p-arg556pro (accessed [today's date]).

Preprint & method: sugi.bio/variant/method Machine-readable: this page as Markdown