Is ALG3 p.Arg277Cys (c.829C>T) pathogenic?

ALG3 p.Arg277Cys (c.829C>T) is classified Uncertain significance in ALG3 (ClinVar, Single submitter, 1 submitter; last evaluated 2025-12-25). AlphaMissense: ambiguous (0.3944); Ultra-rare (popmax 0.0134%, eas); Associated with ALG3-congenital disorder of glycosylation.

What condition is associated with ALG3 p.Arg277Cys (c.829C>T)?

ALG3 p.Arg277Cys (c.829C>T) is associated with ALG3-congenital disorder of glycosylation (ClinVar).

How common is ALG3 p.Arg277Cys (c.829C>T) in the general population?

ALG3 p.Arg277Cys (c.829C>T) is ultra-rare (popmax 0.0134%, eas) (gnomAD).

How is ALG3-CDG inherited?

Typically Autosomal recessive (Orphanet). A genetic counselor can assess individual risk for a family.

What do computational predictors say about ALG3 p.Arg277Cys (c.829C>T)?

AlphaMissense predicts ambiguous (score 0.3944) — an in-silico prediction, not a clinical call.

ALG3 p.Arg277Cys

c.829C>T · VCV4748103

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

ambiguous

0.3944 · ACMG-weighted

gnomAD v4.1

Rare

ultra-rare (popmax 0.0134%, eas)

Missense predictors

2/2 damaging

REVEL, SaProt · AlphaMissense no call

Conditions

ALG3-congenital disorder of glycosylation

Computational evidence

Protein change
AlphaMissense	0.3944	ambiguous
REVEL	0.891	moderately pathogenic-leaning
SaProt	LLR -13.13	damaging
⇒ REVEL and SaProt both call this damaging; AlphaMissense makes no call.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 8.3	GERP 1.7, phastCons 1
Regional constraint	o/e 0.82	unconstrained · MANE · 2,165 bp · p 0.0031 · regional, not allelic
Overall
CADD	33.0	PHRED · no single calibrated threshold — expert panels disagree

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

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0134% East Asian · 6/44,884 alleles

Filtering AF 0.00579% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00394%

Overall 0.000616% 9/1,461,626 alleles · ultra-rare

Ancestry group	Frequency	1 in
East Asiangrpmax	0.0134%	7,481
South Asian	0.0022%	45,542
Remaining individualsnot grpmax-eligible	0.0016%	62,480

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: ALG3
Protein: p.Arg277Cys
Coding: c.829C>T
MANE Select: NM_005787
Type: single nucleotide variant
Location: chr3:184243894 (GRCh38)
Gene constraint: LOEUF 0.972 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 89.05

Full ALG3 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

ALG3-congenital disorder of glycosylation — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For ALG3-CDG (Orphanet):

Inheritance: Autosomal recessive
Onset: Infancy, Neonatal

Similar variants

ALG3 p.Arg277His Uncertain significance ★ ⚠ same residue
ALG3 c.444+1G>T Likely pathogenic ★★ same condition
ALG3 p.Arg171Gln Pathogenic/Likely pathogenic ★★ same condition
ALG3 p.Arg266Cys Pathogenic ★★ same condition
ALG3 p.Arg354Cys Likely pathogenic ★★ same condition
ALG3 p.Arg354His Pathogenic/Likely pathogenic ★★ same condition
ALG3 p.Asn174Ser Likely pathogenic ★★ ⚠ same condition
ALG3 p.Gly55= 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/alg3-p-arg277cys (accessed [today's date]).

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