Is SIX3 p.Ala177= (c.531C>G) pathogenic?

SIX3 p.Ala177= (c.531C>G) is classified Likely benign in SIX3 (ClinVar, Single submitter, 1 submitter; last evaluated 2025-02-19). Very rare (popmax 0.00161%, nfe); Associated with holoprosencephaly 2.

What condition is associated with SIX3 p.Ala177= (c.531C>G)?

SIX3 p.Ala177= (c.531C>G) is associated with holoprosencephaly 2 (ClinVar).

How common is SIX3 p.Ala177= (c.531C>G) in the general population?

SIX3 p.Ala177= (c.531C>G) is very rare (popmax 0.00161%, nfe) (gnomAD).

SIX3 p.Ala177=

c.531C>G · VCV4740628

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00161%, 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 0.4	GERP -3.9, phastCons 0.99
Overall
CADD	12.98	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00161% European (non-Finnish) · 19/1,178,458 alleles

Filtering AF 0.00103% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000831%

Overall 0.00132% 21/1,595,886 alleles · very rare

Ancestry group	Frequency	1 in
European (non-Finnish)grpmax	0.00161%	62,024
African / African-American	0.00134%	74,878
South Asian	0.0011%	90,598

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.Ala177=
Coding: c.531C>G
MANE Select: NM_005413
Type: single nucleotide variant
Location: chr2:44942635 (GRCh38)
Gene constraint: LOEUF 0.387 · pLI 0.99 · ClinGen HI 3/3 (gnomAD)
Structure: AlphaFold pLDDT 70.38

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.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
SIX3 p.Gly317Ser 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-ala177 (accessed [today's date]).

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