# NM_000064.4(C3):c.1677C>T (p.Cys559=)

https://sugi.bio/variant/c3-p-cys559

## Summary

**C3 p.Cys559= (c.1677C>T)** is classified **Likely benign** in C3 (ClinVar, Multiple submitters, 3 submitters; last evaluated 2026-04-06). Very rare (popmax 0.00263%, nfe); Associated with atypical hemolytic-uremic syndrome.

**At a glance:** Likely benign · review: Multiple submitters · rsID rs759423157 · 3 submitters · 3 linked conditions · very rare (popmax 0.00263%, nfe)

## For patients & families {#patients}

This is a change in the C3 gene that is classified as likely benign — not considered disease-causing, submitted by 3 submitters, and is linked to atypical hemolytic-uremic syndrome.

*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 dominant, Autosomal recessive, Not applicable |
| Age of onset (of this condition) | All ages |
| Prevalence | 1-9 / 1 000 000 (United States) |
| Clinical trials | 40 registered for this condition — see ClinicalTrials.gov |
| Diagnostic panels | C3 is a diagnostic-grade gene on 7 Genomics England panels |

**Commonly reported features of Atypical hemolytic uremic syndrome** (across patients with this condition; presentation varies — frequencies from Orphanet):

- Proteinuria — Very frequent (99-80%)
- Hematuria — Very frequent (99-80%)
- Abnormality of blood and blood-forming tissues — Very frequent (99-80%)
- Thrombocytopenia — Very frequent (99-80%)
- Acute kidney injury — Very frequent (99-80%)
- Microangiopathic hemolytic anemia — Very frequent (99-80%)
- Abnormality of metabolism/homeostasis — Very frequent (99-80%)
- Abnormal lactate dehydrogenase activity — Very frequent (99-80%)

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0008702/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [C3](https://sugi.bio/atlas/gene/C3/) |
| Protein change (HGVS p.) | p.Cys559= |
| Coding change (HGVS c.) | c.1677C>T |
| MANE Select transcript | [NM_000064](https://www.ncbi.nlm.nih.gov/nuccore/NM_000064) |
| dbSNP | [rs759423157](https://www.ncbi.nlm.nih.gov/snp/rs759423157/) |
| Variant type | single nucleotide variant |
| Location | chr19:6710648-6710648 (GRCh38) |
| ClinVar | [VCV1647760](https://www.ncbi.nlm.nih.gov/clinvar/variation/1647760/) |

**All HGVS expressions:** `LRG_27:g.15004C>T`, `NC_000019.10:g.6710648G>A`, `NC_000019.9:g.6710659G>A`, `NG_009557.1:g.15004C>T`, `NM_000064.4:c.1677C>T`

## Computational & population evidence {#evidence}

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

- **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 -1.778, GERP -3.18 — not a conserved position (phyloP < 0.1, ACGS BP7 cut)
- CADD: **PHRED 0.874**. 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 **0.00263%** (nfe) · FAF95 0.00188% · FAF99 0.00164% · 31/1,179,620 in the highest group · 38/1,612,696 alleles overall — very rare (popmax 0.00263%, nfe).

| Ancestry group | Allele frequency | 1 in |
| --- | --- | --- |
| Remaining individuals (not grpmax-eligible) | 0.00961% | 10,405 |
| European (non-Finnish) (grpmax) | 0.00263% | 38,052 |
| Admixed American | 0.00167% | 59,972 |

Remaining individuals 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}

**C3** population constraint: LOEUF 0.541, pLI 1.2692e-06, missense-Z 4.4464. *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):

- **C3 glomerulonephritis** — Moderate (AD)
- **atypical hemolytic-uremic syndrome with C3 anomaly** — Definitive (AD)

## Protein context {#protein}

Residue **559** lies in a disulfide bond.

AlphaFold model confidence (whole protein): pLDDT 79.84, 23% of residues very-high.

**80 experimental structure(s)** (PDB): [11MG](https://www.rcsb.org/structure/11MG), [11MH](https://www.rcsb.org/structure/11MH), [1C3D](https://www.rcsb.org/structure/1C3D), [1GHQ](https://www.rcsb.org/structure/1GHQ), [1W2S](https://www.rcsb.org/structure/1W2S), [2A73](https://www.rcsb.org/structure/2A73) — incl. mutant structure 3RJ3.

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

*Describes the biological roles of C3 (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:** C3's established molecular role includes C5L2 anaphylatoxin chemotactic receptor binding. In Reactome, C3 is annotated in disease pathway(s) including **Purinergic signaling in leishmaniasis infection**.

**Disease mechanism (Reactome):** C3 loss or alteration is curated in [Purinergic signaling in leishmaniasis infection](https://reactome.org/content/detail/R-HSA-9660826).

### Pathways affected {#pathways}

C3 participates in **11 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [Purinergic signaling in leishmaniasis infection](https://reactome.org/content/detail/R-HSA-9660826) | curated |
| [Activation of C3 and C5](https://reactome.org/content/detail/R-HSA-174577) | curated |
| [Alternative complement activation](https://reactome.org/content/detail/R-HSA-173736) | curated |
| [G alpha (i) signalling events](https://reactome.org/content/detail/R-HSA-418594) | curated |
| [Immunoregulatory interactions between a Lymphoid and a non-Lymphoid cell](https://reactome.org/content/detail/R-HSA-198933) | curated |
| [Neutrophil degranulation](https://reactome.org/content/detail/R-HSA-6798695) | curated |
| [Peptide ligand-binding receptors](https://reactome.org/content/detail/R-HSA-375276) | curated |
| [Post-translational protein phosphorylation](https://reactome.org/content/detail/R-HSA-8957275) | curated |
| [Regulation of Complement cascade](https://reactome.org/content/detail/R-HSA-977606) | curated |
| [Regulation of Insulin-like Growth Factor (IGF) transport and uptake by Insulin-like Growth Factor Binding Proteins (IGFBPs)](https://reactome.org/content/detail/R-HSA-381426) | curated |
| [Affinity selection of immunoglobulins](https://reactome.org/content/detail/R-HSA-9938027) | electronic |

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

**Molecular function:** C5L2 anaphylatoxin chemotactic receptor binding, receptor ligand activity.

**Biological process:** positive regulation of protein phosphorylation, complement activation, positive regulation of vascular endothelial growth factor production, positive regulation of D-glucose transmembrane transport, regulation of triglyceride biosynthetic process, positive regulation of lipid storage.

## Clinical significance {#significance}

**Likely benign** — review status Multiple submitters *(criteria provided, multiple submitters, no conflicts)*, last evaluated 2026-04-06.

**Submitter consensus:** unanimous (3/3 Likely benign).

**Submission history:** 3 submissions (2025–2026); classifications have been stable.

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Genomenon, Inc, Genomenon, Inc | Likely benign | criteria provided, single submitter | curation | 2025-09-30 |
| Labcorp Genetics (formerly Invitae), Labcorp | Likely benign | criteria provided, single submitter | clinical testing | 2025-02-24 |
| Women's Health and Genetics/Laboratory Corporation of America, LabCorp | Likely benign | criteria provided, single submitter | clinical testing | 2026-04-06 |

## Associated conditions {#conditions}

[atypical hemolytic-uremic syndrome](https://sugi.bio/atlas/disease/atypical-hemolytic-uremic-syndrome/), [complement component 3 deficiency](https://sugi.bio/atlas/disease/complement-component-3-deficiency/), [C3 glomerulonephritis](https://sugi.bio/atlas/disease/c3-glomerulonephritis/).

**Reported phenotype names (ClinVar):** Atypical hemolytic-uremic syndrome, not provided, C3 glomerulonephritis, Complement component 3 deficiency, not specified, AllHighlyPenetrant, Nephropathy due to CFHR5 Deficiency, C3 GLOMERULOPATHY 3, none provided.

## Similar variants {#similar}

Related C3 variant pages (same residue, condition, or type): [C3 c.1003+1G>A](/variant/c3-c-1003-plus-1g-a), [C3 c.2863+1G>T](/variant/c3-c-2863-plus-1g-t), [C3 c.4030-2A>G](/variant/c3-c-4030-minus-2a-g), [C3 p.Arg161Trp](/variant/c3-p-arg161trp), [C3 p.Arg592Gln](/variant/c3-p-arg592gln), [C3 p.Arg592Trp](/variant/c3-p-arg592trp), [C3 p.Arg764Ter](/variant/c3-p-arg764ter), [C3 p.Ile1157Thr](/variant/c3-p-ile1157thr).

### 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 1647760). 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.*