# NM_054012.4(ASS1):c.501C>T (p.His167=)

https://sugi.bio/variant/ass1-p-his167

## Summary

**ASS1 p.His167= (c.501C>T)** is classified **Benign** in ASS1 (ClinVar, Multiple submitters, 10 submitters; last evaluated 2026-02-04). Common (popmax 12.5%, nfe) — too common for a highly-penetrant pathogenic allele; Associated with citrullinemia.

**At a glance:** Benign · review: Multiple submitters · rsID rs10901072 · 10 submitters · 2 linked conditions · common (popmax 12.5%, nfe) — too common for a highly-penetrant pathogenic allele

## For patients & families {#patients}

This is a change in the ASS1 gene that is classified as benign — not considered disease-causing, submitted by 10 submitters, and is linked to citrullinemia.

*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.*

|  |  |
| --- | --- |
| Clinical trials | 6 registered for this condition — see ClinicalTrials.gov |

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0016522/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [ASS1](https://sugi.bio/atlas/gene/ASS1/) |
| Protein change (HGVS p.) | p.His167= |
| Coding change (HGVS c.) | c.501C>T |
| MANE Select transcript | [NM_054012](https://www.ncbi.nlm.nih.gov/nuccore/NM_054012) |
| dbSNP | [rs10901072](https://www.ncbi.nlm.nih.gov/snp/rs10901072/) |
| Variant type | single nucleotide variant |
| Location | chr9:130470839-130470839 (GRCh38) |
| ClinVar | [VCV92369](https://www.ncbi.nlm.nih.gov/clinvar/variation/92369/) |

**All HGVS expressions:** `NC_000009.11:g.133346226C>T`, `NC_000009.12:g.130470839C>T`, `NG_011542.1:g.31133C>T`, `NM_000050.4:c.501C>T`, `NM_054012.4:c.501C>T`

## Computational & population evidence {#evidence}

**Concordance:** Evidence sources **disagree** — common (popmax 12.5%, nfe) — too common for a highly-penetrant pathogenic allele.

- **Missense predictors (AlphaMissense/REVEL/SaProt) do not apply** to this variant type — they score amino-acid substitutions only. For non-missense variants the computational signal comes from conservation (below), not from a missing predictor score.
- Conservation: phyloP -12.097, GERP -2.25 — fast-evolving / accelerated position
- CADD: **PHRED 0.319**. 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.*
- 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 **12.5%** (nfe) · FAF95 12.4% · FAF99 12.4% · 147,107/1,179,710 in the highest group · 197,122/1,613,678 alleles overall — common (popmax 12.5%, nfe) — too common for a highly-penetrant pathogenic allele.

| Ancestry group | Allele frequency | 1 in |
| --- | --- | --- |
| Finnish (not grpmax-eligible) | 19.3% | 5 |
| Amish (not grpmax-eligible) | 13.4% | 7 |
| European (non-Finnish) (grpmax) | 12.5% | 8 |
| South Asian | 12.1% | 8 |
| Remaining individuals (not grpmax-eligible) | 12% | 8 |
| Middle Eastern | 11.9% | 8 |
| African / African-American | 11.9% | 8 |
| Ashkenazi Jewish (not grpmax-eligible) | 11.8% | 8 |
| Admixed American | 7.77% | 13 |
| East Asian | 2.78% | 36 |

Finnish shows a higher raw frequency than the grpmax group. gnomAD excludes bottlenecked groups — Finnish, Ashkenazi Jewish, Amish and "Remaining individuals" — from grpmax, because founder effects make their frequencies unrepresentative for filtering. The table is sorted by frequency, so an excluded group can sit above the grpmax row.

*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}

**ASS1** population constraint: LOEUF 1.14, pLI 1.4303e-18, missense-Z 1.8142. *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):

- **citrullinemia type I** — Definitive (AR)

## Protein context {#protein}

Residue **167** lies in a UniProt-annotated variant site (in ctln1).

AlphaFold model confidence (whole protein): pLDDT 95.64, 91% of residues very-high.

**1 experimental structure(s)** (PDB): [2NZ2](https://www.rcsb.org/structure/2NZ2).

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

*Describes the biological roles of ASS1 (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:** ASS1's established molecular role includes RNA binding. In Reactome, ASS1 is annotated in disease pathway(s) including **ASS1 variants cause citrullinemia**.

**Disease mechanism (Reactome):** ASS1 loss or alteration is curated in [ASS1 variants cause citrullinemia](https://reactome.org/content/detail/R-HSA-9956520).

### Pathways affected {#pathways}

ASS1 participates in **2 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [ASS1 variants cause citrullinemia](https://reactome.org/content/detail/R-HSA-9956520) | curated |
| [Urea cycle](https://reactome.org/content/detail/R-HSA-70635) | curated |

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

**Molecular function:** RNA binding, argininosuccinate synthase activity, amino acid binding, identical protein binding.

**Biological process:** urea cycle, obsolete citrulline metabolic process, obsolete argininosuccinate metabolic process, L-arginine biosynthetic process, aspartate metabolic process, circadian rhythm.

## Clinical significance {#significance}

**Benign** — review status Multiple submitters *(criteria provided, multiple submitters, no conflicts)*, last evaluated 2026-02-04.

**Submitter consensus:** conflicting (9 Benign, 1 Likely benign).

**Submission history:** 10 submissions (2012–2026); classifications have differed over time.

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Genetic Services Laboratory, University of Chicago | Likely benign | no assertion criteria provided | clinical testing |  |
| GeneDx | Benign | criteria provided, single submitter | clinical testing | 2013-06-18 |
| PreventionGenetics, part of Exact Sciences | Benign | criteria provided, single submitter | clinical testing |  |
| Genome-Nilou Lab | Benign | criteria provided, single submitter | clinical testing | 2021-07-01 |
| Mayo Clinic Laboratories, Mayo Clinic | Benign | criteria provided, single submitter | clinical testing | 2021-10-17 |
| Labcorp Genetics (formerly Invitae), Labcorp | Benign | criteria provided, single submitter | clinical testing | 2026-02-04 |
| Natera, Inc. | Benign | no assertion criteria provided | clinical testing | 2017-03-28 |
| Eurofins Ntd Llc (ga) | Benign | criteria provided, single submitter | clinical testing | 2012-12-03 |
| Illumina Laboratory Services, Illumina | Benign | criteria provided, single submitter | clinical testing | 2018-01-13 |
| Breakthrough Genomics, Breakthrough Genomics | Benign | criteria provided, single submitter | not provided |  |

## Associated conditions {#conditions}

[citrullinemia](https://sugi.bio/atlas/disease/citrullinemia/), [citrullinemia type I](https://sugi.bio/atlas/disease/citrullinemia-type-i/).

**Reported phenotype names (ClinVar):** Citrullinemia, not specified, Citrullinemia type I, not provided, AllHighlyPenetrant, none provided, ASS DEFICIENCY, argininosuccinate synthetase deficiency.

## Similar variants {#similar}

Related ASS1 variant pages (same residue, condition, or type): [ASS1 p.His167Arg](/variant/ass1-p-his167arg), [ASS1 c.1194-1G>C](/variant/ass1-c-1194-minus-1g-c), [ASS1 c.174+1G>A](/variant/ass1-c-174-plus-1g-a), [ASS1 c.174+1G>T](/variant/ass1-c-174-plus-1g-t), [ASS1 c.175-1119G>A](/variant/ass1-c-175-minus-1119g-a), [ASS1 c.364-2A>C](/variant/ass1-c-364-minus-2a-c), [ASS1 c.364-2A>G](/variant/ass1-c-364-minus-2a-g), [ASS1 c.364-2A>T](/variant/ass1-c-364-minus-2a-t).

### 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 92369). 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.*