Is SIX3 p.Arg222= (c.664C>A) pathogenic?

SIX3 p.Arg222= (c.664C>A) is classified Likely benign in SIX3 (ClinVar, Single submitter, 1 submitter; last evaluated 2022-11-01). Very rare (popmax 0.00492%, nfe); Associated with holoprosencephaly 2.

What condition is associated with SIX3 p.Arg222= (c.664C>A)?

SIX3 p.Arg222= (c.664C>A) is associated with holoprosencephaly 2 (ClinVar).

How common is SIX3 p.Arg222= (c.664C>A) in the general population?

SIX3 p.Arg222= (c.664C>A) is very rare (popmax 0.00492%, nfe) (gnomAD).

SIX3 p.Arg222=

c.664C>A · rs748952099 · VCV1672129

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00492%, nfe)

Conditions

holoprosencephaly 2

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 1.1	GERP -0.21, phastCons 1
Overall
CADD	13.4	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00492% European (non-Finnish) · 58/1,179,798 alleles

Filtering AF 0.00386% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00353%

Overall 0.00381% 61/1,600,278 alleles · very rare exomes 60/1,448,060 · genomes 1/152,218 · joint denominator

Ancestry group	Frequency	1 in
European (non-Finnish)grpmax	0.00492%	20,341
East Asian	0.00223%	44,882
Finnishnot grpmax-eligible	0.00198%	50,606
Remaining individualsnot grpmax-eligible	0.0016%	62,396

Rarity supports pathogenicity (ACMG PM2); frequency above a disease-specific BA1/BS1 threshold argues against it. A variant frequent in one ancestry group can be near-absent in others, so a single global figure can mislead.

Variant & gene context

Gene: SIX3
Protein: p.Arg222=
Coding: c.664C>A
MANE Select: NM_005413
dbSNP: rs748952099
Type: single nucleotide variant
Location: chr2:44942768 (GRCh38)
Gene constraint: LOEUF 0.387 · pLI 0.99 · ClinGen HI 3/3 (gnomAD)
Structure: AlphaFold pLDDT 70.38
Residue 222: a DNA-binding region

Full SIX3 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

holoprosencephaly 2 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Similar variants

SIX3 p.Arg222Gln Uncertain significance ★ ⚠ same residue
SIX3 p.Ala72Val Uncertain significance ★★ ⚠ same condition
SIX3 p.Arg146Cys Uncertain significance ★★ ⚠ same condition
SIX3 p.Arg201His Uncertain significance ★★ ⚠ same condition
SIX3 p.Arg281Ser Uncertain significance ★★ same condition
SIX3 p.Asp205His Uncertain significance ★★ ⚠ same condition
SIX3 p.Gly103Arg Uncertain significance ★★ ⚠ same condition
SIX3 p.Gly244Cys Uncertain significance ★★ ⚠ 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/six3-p-arg222 (accessed [today's date]).

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