# NM_000222.3(KIT):c.2056C>T (p.Arg686Cys)

https://sugi.bio/variant/kit-p-arg686cys

## Summary

**KIT p.Arg686Cys (c.2056C>T)** is classified **Conflicting classifications of pathogenicity** in KIT (ClinVar, Conflicting submitters, 6 submitters; last evaluated 2026-05-29). AlphaMissense: likely pathogenic (0.8726); Very rare (popmax 0.00678%, nfe); Associated with hereditary neoplastic syndrome.

**At a glance:** Conflicting classifications of pathogenicity · review: Conflicting submitters · rsID rs148771698 · 6 submitters · 2 linked conditions · AlphaMissense likely pathogenic · very rare (popmax 0.00678%, nfe)

## For patients & families {#patients}

This is a change in the KIT gene that is of uncertain or conflicting significance (submitters disagree on it), submitted by 6 submitters, and is linked to hereditary neoplastic 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.*

|  |  |
| --- | --- |
| Clinical trials | 31 registered for this condition — see ClinicalTrials.gov |

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0019921/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [KIT](https://sugi.bio/atlas/gene/KIT/) |
| Protein change (HGVS p.) | p.Arg686Cys |
| Coding change (HGVS c.) | c.2056C>T |
| MANE Select transcript | [NM_000222](https://www.ncbi.nlm.nih.gov/nuccore/NM_000222) |
| dbSNP | [rs148771698](https://www.ncbi.nlm.nih.gov/snp/rs148771698/) |
| Variant type | single nucleotide variant |
| Location | chr4:54729400-54729400 (GRCh38) |
| ClinVar | [VCV409744](https://www.ncbi.nlm.nih.gov/clinvar/variation/409744/) |

**All HGVS expressions:** `LRG_307:g.76406C>T`, `LRG_307t1:c.2056C>T`, `NC_000004.11:g.55595566C>T`, `NC_000004.12:g.54729400C>T`, `NG_007456.1:g.76406C>T`, `NM_000222.3:c.2056C>T`, `NM_001093772.2:c.2044C>T`, `NM_001385284.1:c.2059C>T`, `NM_001385285.1:c.2056C>T`, `NM_001385286.1:c.2044C>T`, `NM_001385288.1:c.2047C>T`, `NM_001385290.1:c.2059C>T`, `NM_001385292.1:c.2047C>T`

## Computational & population evidence {#evidence}

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

- AlphaMissense **likely pathogenic** (0.8726)
- REVEL 0.691 (pathogenic-leaning) — agrees with AlphaMissense
- SaProt LLR -10.743 (damaging) — agrees with AlphaMissense
- → **In-silico consensus:** AlphaMissense, REVEL and SaProt all call this damaging
- Conservation: phyloP 6.009, GERP 2.56, phastCons 1 — highly conserved (agrees)
- CADD: **PHRED 34.0**. 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 0.72** across the covering region of the MANE Select transcript (54,727,882–54,731,996), spanning 4,114 bp. Chi-square p 4.1e-05. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI: **below the reporting threshold**. This position is scored for a different substitution (C>A, Δ0.24 acceptor gain), so this allele was evaluated and its deltas all fell under Δ0.2 — a prediction of no splicing effect for this allele, not a gap in our data. *No ACMG code assigned.*
- Population frequency (gnomAD v4.1): grpmax **0.00678%** (nfe) · FAF95 0.00555% · FAF99 0.00514% · 80/1,179,738 in the highest group · 92/1,613,516 alleles overall — very rare (popmax 0.00678%, nfe).

| Ancestry group | Allele frequency | 1 in |
| --- | --- | --- |
| Remaining individuals (not grpmax-eligible) | 0.0112% | 8,922 |
| European (non-Finnish) (grpmax) | 0.00678% | 14,747 |
| Finnish (not grpmax-eligible) | 0.00469% | 21,323 |
| African / African-American | 0.00134% | 74,876 |
| South Asian | 0.0011% | 91,078 |

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}

**KIT** population constraint: LOEUF 0.24, pLI 1, missense-Z 4.1661; ClinGen dosage — haploinsufficiency 3, triplosensitivity 0 (0–3 scale). *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):

- **gastrointestinal stromal tumor** — Definitive (AD)

## Protein context {#protein}

Residue **686** lies in the protein kinase domain; an α-helix.

AlphaFold model confidence (whole protein): pLDDT 78.52, 51% of residues very-high.

**65 experimental structure(s)** (PDB): [12FJ](https://www.rcsb.org/structure/12FJ), [1PKG](https://www.rcsb.org/structure/1PKG), [1T45](https://www.rcsb.org/structure/1T45), [1T46](https://www.rcsb.org/structure/1T46), [2E9W](https://www.rcsb.org/structure/2E9W), [2EC8](https://www.rcsb.org/structure/2EC8) — incl. mutant structure 3G0F.

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

*Describes the biological roles of KIT (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:** KIT's established molecular role includes transmembrane receptor protein tyrosine kinase activity. p.Arg686Cys falls in the protein kinase domain. In Reactome, KIT is annotated in disease pathway(s) including **Constitutive Signaling by Aberrant PI3K in Cancer**, **Dasatinib-resistant KIT mutants**.

**Disease mechanism (Reactome):** KIT loss or alteration is curated in [Constitutive Signaling by Aberrant PI3K in Cancer](https://reactome.org/content/detail/R-HSA-2219530), [Dasatinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669914), [Imatinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669917).

### Pathways affected {#pathways}

KIT participates in **22 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [Constitutive Signaling by Aberrant PI3K in Cancer](https://reactome.org/content/detail/R-HSA-2219530) | curated |
| ⚕ [Dasatinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669914) | curated |
| ⚕ [Imatinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669917) | curated |
| ⚕ [KIT mutants bind TKIs](https://reactome.org/content/detail/R-HSA-9669921) | curated |
| ⚕ [Masitinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669924) | curated |
| ⚕ [Nilotinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669926) | curated |
| ⚕ [Regorafenib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669929) | curated |
| ⚕ [Signaling by extracellular domain mutants of KIT](https://reactome.org/content/detail/R-HSA-9680187) | curated |
| ⚕ [Signaling by juxtamembrane domain KIT mutants](https://reactome.org/content/detail/R-HSA-9669935) | curated |
| ⚕ [Signaling by kinase domain mutants of KIT](https://reactome.org/content/detail/R-HSA-9669933) | curated |
| ⚕ [Signaling by phosphorylated juxtamembrane, extracellular and kinase domain KIT mutants](https://reactome.org/content/detail/R-HSA-9670439) | curated |
| ⚕ [Sorafenib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669936) | curated |
| ⚕ [Sunitinib-resistant KIT mutants](https://reactome.org/content/detail/R-HSA-9669934) | curated |
| [Developmental Lineage of Mammary Gland Alveolar Cells](https://reactome.org/content/detail/R-HSA-9927426) | curated |
| [Developmental Lineage of Mammary Gland Luminal Epithelial Cells](https://reactome.org/content/detail/R-HSA-9927418) | curated |
| [PI5P, PP2A and IER3 Regulate PI3K/AKT Signaling](https://reactome.org/content/detail/R-HSA-6811558) | curated |
| [PIP3 activates AKT signaling](https://reactome.org/content/detail/R-HSA-1257604) | curated |
| [RAF/MAP kinase cascade](https://reactome.org/content/detail/R-HSA-5673001) | curated |
| [TFAP2 (AP-2) family regulates transcription of growth factors and their receptors](https://reactome.org/content/detail/R-HSA-8866910) | curated |
| [Transcriptional and post-translational regulation of MITF-M expression and activity](https://reactome.org/content/detail/R-HSA-9856649) | curated |
| [Regulation of KIT signaling](https://reactome.org/content/detail/R-HSA-1433559) | electronic |
| [Signaling by SCF-KIT](https://reactome.org/content/detail/R-HSA-1433557) | electronic |

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

**Molecular function:** transmembrane receptor protein tyrosine kinase activity, cytokine binding, protein homodimerization activity.

**Biological process:** mast cell chemotaxis, male gonad development, cytokine-mediated signaling pathway, actin cytoskeleton organization, positive regulation of mast cell cytokine production, Fc receptor signaling pathway.

## Clinical significance {#significance}

**Conflicting classifications of pathogenicity** — review status Conflicting submitters *(criteria provided, conflicting classifications)*, last evaluated 2026-05-29.

**Submitter consensus:** conflicting (4 Uncertain significance, 1 Likely benign).

**Submission history:** 6 submissions (2023–2026); classifications have differed over time.

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| GeneDx | Uncertain significance | criteria provided, single submitter | clinical testing | 2023-05-17 |
| Ambry Genetics | Uncertain significance | criteria provided, single submitter | clinical testing | 2024-07-26 |
| Labcorp Genetics (formerly Invitae), Labcorp | Uncertain significance | criteria provided, single submitter | clinical testing | 2026-01-19 |
| St. Jude Molecular Pathology, St. Jude Children's Research Hospital | Uncertain significance | criteria provided, single submitter | clinical testing | 2023-12-24 |
| Center for Genomic Medicine, Rigshospitalet, Copenhagen University Hospital |  | criteria provided, single submitter | clinical testing | 2025-12-29 |
| Myriad Genetics, Inc. | Likely benign | criteria provided, single submitter | clinical testing | 2026-05-29 |

## Associated conditions {#conditions}

[hereditary neoplastic syndrome](https://sugi.bio/atlas/disease/hereditary-neoplastic-syndrome/), [gastrointestinal stromal tumor](https://sugi.bio/atlas/disease/gastrointestinal-stromal-tumor/).

**Reported phenotype names (ClinVar):** Hereditary cancer-predisposing syndrome, Gastrointestinal stromal tumor, not provided, Neoplasm, Neoplastic Syndromes, Hereditary, Hereditary Cancer Syndrome, Hereditary neoplastic syndrome, Tumor predisposition, Gastrointestinal stroma tumor, Gastrointestinal stromal tumor, somatic.

## Similar variants {#similar}

Related KIT variant pages (same residue, condition, or type): [KIT p.Arg686Leu](/variant/kit-p-arg686leu), [KIT p.Arg686His](/variant/kit-p-arg686his), [KIT p.Arg686=](/variant/kit-p-arg686), [KIT p.Ala621Thr](/variant/kit-p-ala621thr), [KIT p.Asp820Tyr](/variant/kit-p-asp820tyr), [KIT p.Gln190Ter](/variant/kit-p-gln190ter), [KIT p.Leu576Pro](/variant/kit-p-leu576pro), [KIT p.Lys642Glu](/variant/kit-p-lys642glu).

### 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 409744). 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.*