# NM_019109.5(ALG1):c.841G>T (p.Val281Phe)

https://sugi.bio/variant/alg1-p-val281phe

## Summary

**ALG1 p.Val281Phe (c.841G>T)** is classified **Pathogenic/Likely pathogenic** in ALG1 (ClinVar, Multiple submitters, 5 submitters; last evaluated 2026-01-17). AlphaMissense: ambiguous (0.4582); Ultra-rare (popmax 0.01%, amr); Associated with ALG1-congenital disorder of glycosylation.

**At a glance:** Pathogenic/Likely pathogenic · review: Multiple submitters · rsID rs553396382 · 5 submitters · 2 linked conditions · AlphaMissense ambiguous · ultra-rare (popmax 0.01%, amr)

## For patients & families {#patients}

This is a change in the ALG1 gene that is considered likely disease-causing, submitted by 5 submitters, and is linked to ALG1-congenital disorder of glycosylation.

*Reference information, not medical advice, and not a prediction for any individual. A genetic counselor or clinician can interpret what it means for you and your family.*

|  |  |
| --- | --- |
| Typical inheritance (of this condition) | Autosomal recessive |
| Age of onset (of this condition) | Infancy, Neonatal |
| Diagnostic panels | ALG1 is a diagnostic-grade gene on 12 Genomics England panels |

**Commonly reported features of ALG1-CDG** (across patients with this condition; presentation varies — frequencies from Orphanet):

- Intellectual disability — Very frequent (99-80%)
- Seizure — Very frequent (99-80%)
- Hypotonia — Very frequent (99-80%)
- Global developmental delay — Very frequent (99-80%)
- Progressive microcephaly — Frequent (79-30%)
- Abnormality of the eye — Frequent (79-30%)
- Strabismus — Frequent (79-30%)
- Abnormality of the skeletal system — Frequent (79-30%)

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0009838/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [ALG1](https://sugi.bio/atlas/gene/ALG1/) |
| Protein change (HGVS p.) | p.Val281Phe |
| Coding change (HGVS c.) | c.841G>T |
| MANE Select transcript | [NM_019109](https://www.ncbi.nlm.nih.gov/nuccore/NM_019109) |
| dbSNP | [rs553396382](https://www.ncbi.nlm.nih.gov/snp/rs553396382/) |
| Variant type | single nucleotide variant |
| Location | chr16:5078857-5078857 (GRCh38) |
| ClinVar | [VCV690317](https://www.ncbi.nlm.nih.gov/clinvar/variation/690317/) |

**All HGVS expressions:** `NC_000016.10:g.5078857G>T`, `NC_000016.9:g.5128858G>T`, `NG_009202.1:g.12049G>T`, `NM_001330504.2:c.508G>T`, `NM_019109.5:c.841G>T`

## Computational & population evidence {#evidence}

**Concordance:** AlphaMissense makes no call; REVEL and SaProt both call this damaging; AlphaMissense makes no call — descriptive only.

- AlphaMissense **ambiguous** (0.4582) — no call either way
- REVEL 0.703 (pathogenic-leaning)
- SaProt LLR -14.984 (damaging)
- → **In-silico consensus:** REVEL and SaProt both call this damaging; AlphaMissense makes no call
- SpliceAI predicts **donor loss** (Δ 0.20) — consistent with the pathogenic call
- Conservation: phyloP 5.82, GERP -0.677, phastCons 1 — highly conserved
- CADD: **PHRED 23.3**. No single ClinGen-calibrated threshold exists and the expert panels that use CADD disagree — GUCY2D/AIPL1 require ≥ 20.0 for an untranslated-region variant, ABCA4 ≥ 28.1 for a synonymous or indel variant, the Pulmonary Hypertension panel imports Pejaver 2022's missense-calibrated numbers, and the Antibody Deficiencies panel declines CADD entirely for PIK3CD. CADD v1.7 also incorporates Zoonomia phyloP, so it partly re-expresses the conservation above. *Descriptive; no threshold applied.*
- Regional missense constraint: **o/e 1.27** across the covering region of the MANE Select transcript (5,071,850–5,084,878), spanning 13,028 bp. Chi-square p 3.2e-11. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI deltas (raw): acceptor loss **0.00**, donor loss **0.20**, acceptor gain **0.00**, donor gain **0.01**. Largest is donor loss, 1 bp away.
- SpliceAI deltas (masked): acceptor loss **0.00**, donor loss **0.00**, acceptor gain **0.00**, donor gain **0.01**.
  Masked SpliceAI — what Ensembl VEP and the Broad lookup serve by default — is below the reporting threshold here, so those tools show **no splice signal** for this allele. Masking zeroes a loss scored against a position that is not an annotated splice site, and a gain that merely strengthens an existing one, so the raw score above is describing a cryptic site rather than the site the variant sits on. *No ACMG code is assigned either way.*
- Population frequency (gnomAD v4.1): grpmax **0.01%** (amr) · FAF95 0.00428% · FAF99 0.00295% · 6/59,980 in the highest group · 6/1,611,626 alleles overall — ultra-rare (popmax 0.01%, amr).

*Computational predictors are not independent (ClinGen Variant Classification guidance): AlphaMissense (Cheng et al. 2023) carries the ACMG weight for missense and conservation (phyloP/GERP/phastCons) for non-missense; REVEL (Pejaver-2022 calibrated strength bands) and SaProt (Su et al. 2023, structure-aware, ClinVar-independent protein language model, raw LLR) are shown as orthogonal agreement signals, not additive. For frequency, the gnomAD v4.1 grpmax filtering allele frequency (FAF95) is ClinGen's designated BA1/BS1 input (gnomAD v4 guidance v3.0, June 2025); BA1/BS1 thresholds are disease-specific, not a blanket 5%. Predictions, not a clinical determination.*

## Gene constraint & dosage {#gene-context}

**ALG1** population constraint: LOEUF 1.419, pLI 1.6267e-25, missense-Z -2.6689; ClinGen dosage — haploinsufficiency gene assoc. with recessive phenotype, triplosensitivity Not yet evaluated/3. *Lower LOEUF and higher pLI indicate a gene that tolerates loss-of-function poorly; ClinGen dosage is the curated haploinsufficiency call.*

Curated gene–disease validity (ClinGen):

- **ALG1-congenital disorder of glycosylation** — Definitive (AR)

## Protein context {#protein}

Residue **281** lies in a UniProt-annotated variant site (in cdg1k; decreased function in protein glycosylation as shown by rescue assays in an alg1-deficient yeast strain).

AlphaFold model confidence (whole protein): pLDDT 93.24, 83% of residues very-high.

## What this gene does {#gene-function}

*Describes the biological roles of ALG1 (the gene this variant disrupts) — not effects measured for this specific variant. A damaging variant is expected to affect these functions and pathways; the degree depends on the variant.*

**How this variant is thought to act:** ALG1's established molecular role includes chitobiosyldiphosphodolichol beta-mannosyltransferase activity. In Reactome, ALG1 is annotated in disease pathway(s) including **Defective ALG1 causes CDG-1k**.

**Disease mechanism (Reactome):** ALG1 loss or alteration is curated in [Defective ALG1 causes CDG-1k](https://reactome.org/content/detail/R-HSA-4549380).

### Pathways affected {#pathways}

ALG1 participates in **2 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [Defective ALG1 causes CDG-1k](https://reactome.org/content/detail/R-HSA-4549380) | curated |
| [Biosynthesis of the N-glycan precursor (dolichol lipid-linked oligosaccharide, LLO) and transfer to a nascent protein](https://reactome.org/content/detail/R-HSA-446193) | curated |

### Molecular function & processes (GO — experimentally supported) {#go}

**Molecular function:** chitobiosyldiphosphodolichol beta-mannosyltransferase activity.

**Biological process:** protein N-linked glycosylation, dolichol-linked oligosaccharide biosynthetic process.

## Clinical significance {#significance}

**Pathogenic/Likely pathogenic** — review status Multiple submitters *(criteria provided, multiple submitters, no conflicts)*, last evaluated 2026-01-17.

**Submitter consensus:** conflicting (4 Likely pathogenic, 1 Pathogenic).

**Submission history:** 5 submissions (2017–2026); classifications have differed over time.

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| University of Washington Center for Mendelian Genomics, University of Washington | Likely pathogenic | no assertion criteria provided | research | 2017-05-25 |
| Fulgent Genetics, Fulgent Genetics | Likely pathogenic | criteria provided, single submitter | clinical testing | 2024-02-05 |
| Labcorp Genetics (formerly Invitae), Labcorp | Pathogenic | criteria provided, single submitter | clinical testing | 2026-01-08 |
| 3billion | Likely pathogenic | criteria provided, single submitter | clinical testing | 2025-05-28 |
| GeneDx | Likely pathogenic | criteria provided, single submitter | clinical testing | 2026-01-17 |

## Associated conditions {#conditions}

[ALG1-congenital disorder of glycosylation](https://sugi.bio/atlas/disease/alg1-congenital-disorder-of-glycosylation/), [congenital disorder of glycosylation](https://sugi.bio/atlas/disease/congenital-disorder-of-glycosylation/).

**Reported phenotype names (ClinVar):** ALG1-congenital disorder of glycosylation, Congenital disorder of glycosylation, not provided, none provided, Congenital disorders of glycosylation, Carbohydrate-deficient glycoprotein syndrome, ALG1-CDG, CONGENITAL DISORDER OF GLYCOSYLATION, TYPE Ik, CDG Ik.

## Similar variants {#similar}

Related ALG1 variant pages (same residue, condition, or type): [ALG1 p.Val281=](/variant/alg1-p-val281), [ALG1 c.1187+1G>A](/variant/alg1-c-1187-plus-1g-a), [ALG1 c.1187+2T>C](/variant/alg1-c-1187-plus-2t-c), [ALG1 c.1188-2A>G](/variant/alg1-c-1188-minus-2a-g), [ALG1 c.209-2A>G](/variant/alg1-c-209-minus-2a-g), [ALG1 c.539+1G>A](/variant/alg1-c-539-plus-1g-a), [ALG1 c.630-2A>G](/variant/alg1-c-630-minus-2a-g), [ALG1 c.863-2A>G](/variant/alg1-c-863-minus-2a-g).

### Data sources & attribution {#sources}

ClinVar (NCBI — public domain, built 2026-10-14); gnomAD v4.1 (Broad Institute, built 2026-10-06); AlphaMissense (Cheng et al. 2023, © Google DeepMind — CC BY 4.0, built 2026-01-27); REVEL (Ioannidis et al. 2016 — ODbL, built 2026-07-13); SaProt (Su et al. 2023 — MIT, built 2026-10-14); SpliceAI (Illumina — free for non-commercial use, built 2026-10-13); CADD (Rentzsch et al. 2019, University of Washington — free for non-commercial use, built 2026-10-10); Conservation (phyloP/phastCons/GERP) (UCSC hg38 470-way mammal (Hiller Lab) + Ensembl Compara, built 2026-07-12); gnomAD Non-coding Constraint (Gnocchi) (Chen et al. 2024, Broad Institute — CC0, built 2026-10-11); gnomAD Regional Missense Constraint (Broad Institute — CC0, built 2026-10-13); Pangolin (Zeng & Li 2022 — CC BY 4.0, built 2026-10-11); Repeat regions (UCSC — RepeatMasker, TRF, segmental duplications, built 2026-10-11); ClinGen (ClinGen, built 2026-09-22); UniProt (CC BY 4.0); Reactome / GO (CC BY 4.0, built 2026-09-23); MaveDB (per-record license, built 2026-10-11); CIViC (CC0, built 2026-09-22); Orphanet (Orphanet, built 2026-06-12)

*Primary record: NCBI ClinVar (variation 690317). Classifications reflect these databases as of the page's build date and may change. Free reference use — not medical advice; consult the primary submitters and a clinician.*