# NM_001127895.2(CHST8):c.229C>T (p.Arg77Trp)

https://sugi.bio/variant/chst8-p-arg77trp

## Summary

**CHST8 p.Arg77Trp (c.229C>T)** is classified **Conflicting classifications of pathogenicity** in CHST8 (ClinVar, Conflicting submitters, 6 submitters; last evaluated 2025-05-07). AlphaMissense: likely benign (0.0789); Rare (popmax 0.674%, nfe); Associated with peeling skin syndrome type A.

**At a glance:** Conflicting classifications of pathogenicity · review: Conflicting submitters · rsID rs149660944 · 6 submitters · 1 linked condition · AlphaMissense likely benign · rare (popmax 0.674%, nfe)

## For patients & families {#patients}

This is a change in the CHST8 gene that is of uncertain or conflicting significance (submitters disagree on it), submitted by 6 submitters, and is linked to peeling skin syndrome type A.

*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 |
| Prevalence | <1 / 1 000 000 (Europe) |

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0017258/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [CHST8](https://sugi.bio/atlas/gene/CHST8/) |
| Protein change (HGVS p.) | p.Arg77Trp |
| Coding change (HGVS c.) | c.229C>T |
| MANE Select transcript | [NM_001127895](https://www.ncbi.nlm.nih.gov/nuccore/NM_001127895) |
| dbSNP | [rs149660944](https://www.ncbi.nlm.nih.gov/snp/rs149660944/) |
| Variant type | single nucleotide variant |
| Location | chr19:33772017-33772017 (GRCh38) |
| ClinVar | [VCV183645](https://www.ncbi.nlm.nih.gov/clinvar/variation/183645/) |

**All HGVS expressions:** `NC_000019.10:g.33772017C>T`, `NC_000019.9:g.34262922C>T`, `NG_029857.1:g.155062C>T`, `NM_001127895.2:c.229C>T`, `NM_001127896.2:c.229C>T`, `NM_022467.3:c.229C>T`

## Computational & population evidence {#evidence}

**Concordance:** Mixed / partial computational evidence (see below).

- AlphaMissense **likely benign** (0.0789)
- REVEL 0.401 (indeterminate)
- SaProt LLR -8.402 (tolerated) — agrees with AlphaMissense
- → **In-silico consensus:** AlphaMissense and SaProt both call this tolerated; REVEL makes no call
- Conservation: phyloP -0.712, GERP -0.655 — not a conserved position (phyloP < 0.1, ACGS BP7 cut)
- CADD: **PHRED 14.59**. 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 1.04** across the covering region of the MANE Select transcript (33,689,262–33,773,060), spanning 83,798 bp. Chi-square p 0.3. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI: **not assessed** — no allele at this position is in our SpliceAI release, either because it lies outside the scored MANE transcript scope or because every allele is below Δ0.2. We cannot tell which, so this claims neither; absence is not evidence against a splicing effect.
- Population frequency (gnomAD v4.1): grpmax **0.674%** (nfe) · FAF95 0.661% · FAF99 0.656% · 7,939/1,178,616 in the highest group · 9,173/1,609,794 alleles overall — rare (popmax 0.674%, nfe).

| Ancestry group | Allele frequency | 1 in |
| --- | --- | --- |
| European (non-Finnish) (grpmax) | 0.674% | 148 |
| Remaining individuals (not grpmax-eligible) | 0.541% | 185 |
| South Asian | 0.523% | 191 |
| Admixed American | 0.282% | 355 |
| Finnish (not grpmax-eligible) | 0.267% | 374 |
| Middle Eastern | 0.116% | 864 |
| African / African-American | 0.101% | 985 |
| Ashkenazi Jewish (not grpmax-eligible) | 0.0136% | 7,340 |
| East Asian | 0.00223% | 44,818 |

*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}

**CHST8** population constraint: LOEUF 1.001, pLI 0.0016809, missense-Z -0.32668. *Lower LOEUF and higher pLI indicate a gene that tolerates loss-of-function poorly; ClinGen dosage is the curated haploinsufficiency call.*

## Protein context {#protein}

Residue **77** lies in a UniProt-annotated variant site (according to pubmed:22289416 this variant results in decreased glycosaminoglycan sulfation; according to pubmed:28204496 it does not affect sulfotransferase activity); the 'disordered' region.

AlphaFold model confidence (whole protein): pLDDT 79.90, 62% of residues very-high.

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

*Describes the biological roles of CHST8 (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:** CHST8's established molecular role includes sulfotransferase activity. p.Arg77Trp falls in the disordered region.


### Pathways affected {#pathways}

CHST8 participates in **1 Reactome pathway** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| [Reactions specific to the complex N-glycan synthesis pathway](https://reactome.org/content/detail/R-HSA-975578) | curated |

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

**Molecular function:** sulfotransferase activity.

**Biological process:** sulfur compound metabolic process, proteoglycan biosynthetic process, hormone biosynthetic process.

## Clinical significance {#significance}

**Conflicting classifications of pathogenicity** — review status Conflicting submitters *(criteria provided, conflicting classifications)*, last evaluated 2025-05-07.

**Submitter consensus:** conflicting (3 Uncertain significance, 3 Likely benign).

**Submission history:** 6 submissions (2012–2025); classifications have differed over time.

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Mendelics | Uncertain significance | criteria provided, single submitter | clinical testing | 2019-05-28 |
| Labcorp Genetics (formerly Invitae), Labcorp | Likely benign | criteria provided, single submitter | clinical testing | 2019-12-31 |
| OMIM | Uncertain significance | no assertion criteria provided | literature only | 2012-04-01 |
| PreventionGenetics, part of Exact Sciences | Likely benign | no assertion criteria provided | clinical testing | 2021-05-28 |
| CeGaT Center for Human Genetics Tuebingen | Likely benign | criteria provided, single submitter | clinical testing | 2022-12-01 |
| Mayo Clinic Laboratories, Mayo Clinic | Uncertain significance | criteria provided, single submitter | clinical testing | 2025-05-07 |

## Associated conditions {#conditions}

[peeling skin syndrome type A](https://sugi.bio/atlas/disease/peeling-skin-syndrome-type-a/).

**Reported phenotype names (ClinVar):** Peeling skin syndrome type A, not provided, CHST8-related disorder, CHST8-related condition, Peeling skin syndrome 3, none provided.

## Similar variants {#similar}

Related CHST8 variant pages (same residue, condition, or type): [CHST8 p.Arg77=](/variant/chst8-p-arg77), [CHST8 p.Val186Ala](/variant/chst8-p-val186ala), [CHST8 c.168+64G>A](/variant/chst8-c-168-plus-64g-a), [CHST8 c.-86-36C>T](/variant/chst8-c-minus-86-minus-36c-t), [CHST8 p.Arg9=](/variant/chst8-p-arg9), [CHST8 p.Leu288=](/variant/chst8-p-leu288), [CHST8 p.Ala23Gly](/variant/chst8-p-ala23gly), [CHST8 p.Ala293Pro](/variant/chst8-p-ala293pro).

### Data sources & attribution {#sources}

ClinVar (NCBI — public domain, built 2026-10-11); 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 2026-07-14); 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 183645). 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.*