STT3B
Chr 3ARSTT3 oligosaccharyltransferase complex catalytic subunit B
Also known as: CDG1X, SIMP, STT3-B
STT3B encodes a catalytic subunit of the oligosaccharyl transferase complex that transfers oligosaccharides to asparagine residues during protein N-glycosylation in the endoplasmic reticulum. Mutations cause congenital disorder of glycosylation type Ix, inherited in an autosomal recessive pattern. The gene is highly constrained against loss-of-function variants, indicating that complete loss of function is likely incompatible with normal development.
Limited evidence — not for standalone diagnostic reporting
Population Genetics & Constraint
gnomAD v4 — loss-of-function & missense intolerance
Highly LoF-intolerant (top ~10% of genes)
Highly missense-constrained (top ~0.1%)
Predictions shown for reference only — model trained on dominant genes, not applicable to AR conditions.
The Badonyi & Marsh prediction model was trained exclusively on dominant disease genes. Predictions are not reliable for genes with autosomal recessive inheritance and are shown at reduced opacity for reference only.
Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312. Mechanism ranking also informed by gnomAD constraint, ClinVar, and ClinGen data.
ClinVar Variant Classifications
274 submitted variants in ClinVar
Classification Summary
Curated Variants Distribution
Classified variants from ClinVar · 5 ACMG categories
| Classification | LoF | Missense + Inframe | Non-coding | Synonymous | Total |
|---|---|---|---|---|---|
Pathogenic | 0 | 1 | 16 | 0 | 17 |
Likely Pathogenic | 0 | 0 | 1 | 0 | 1 |
VUS | 0 | 96 | 2 | 1 | 99 |
Likely Benign | 0 | 1 | 45 | 51 | 97 |
Benign | 0 | 1 | 31 | 3 | 35 |
Conflicting | — | 2 | |||
| Total | 0 | 99 | 95 | 55 | 251 |
LoF = frameshift, stop gained/lost, canonical splice · Counts from ClinVar esearch · Updated hourly
View in ClinVar →Protein Context — Lollipop Plot
STT3B · protein map & ClinVar variants
Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.
3D Protein StructureAlphaFold
External Resources
Links to major genomics databases and tools
Clinical Trials
Active and recruiting trials from ClinicalTrials.gov
No active trials found for this gene.
Search ClinicalTrials.gov →External Resources
Links to major genomics databases and tools