# NM_000377.3(WAS):c.1021_1022insT (p.Pro341fs)

https://sugi.bio/variant/was-p-pro341fs

## Summary

**WAS p.Pro341fs (c.1021_1022insT)** is classified **Pathogenic** in WAS (ClinVar, Single submitter, 1 submitter; last evaluated 2021-02-02). No gnomAD frequency available for this variant; Associated with thrombocytopenia 1.

**At a glance:** Pathogenic · review: Single submitter · rsID rs2147266379 · 1 submitter · 3 linked conditions · no gnomAD frequency available for this variant

## For patients & families {#patients}

This is a change in the WAS gene that is reported as disease-causing, but on limited review, submitted by 1 submitter, and is linked to thrombocytopenia 1.

*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 | 22 registered for this condition — see ClinicalTrials.gov |

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0005176/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [WAS](https://sugi.bio/atlas/gene/WAS/) |
| Protein change (HGVS p.) | p.Pro341fs |
| Coding change (HGVS c.) | c.1021_1022insT |
| MANE Select transcript | [NM_000377](https://www.ncbi.nlm.nih.gov/nuccore/NM_000377) |
| dbSNP | [rs2147266379](https://www.ncbi.nlm.nih.gov/snp/rs2147266379/) |
| Variant type | Insertion |
| Location | chrX:48688749-48688750 (GRCh38) |
| ClinVar | [VCV1418621](https://www.ncbi.nlm.nih.gov/clinvar/variation/1418621/) |

**All HGVS expressions:** `LRG_125:g.9953_9954insT`, `NC_000023.10:g.48547138_48547139insT`, `NC_000023.11:g.48688749_48688750insT`, `NG_007877.1:g.9953_9954insT`, `NM_000377.3:c.1021_1022insT`

## Computational & population evidence {#evidence}

**Concordance:** 1 independent predictor **concordant** with the ClinVar classification.

- **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 5.631, GERP 1.23, phastCons 1 — highly conserved position (PP3-type support)
- Molecular consequence: **frameshift** — a predicted loss-of-function variant. ClinGen curates **sufficient evidence for haploinsufficiency** in this gene, supporting a loss-of-function disease mechanism. *Descriptive; not an applied PVS1 code.*
- Nonsense-mediated decay: the premature termination codon is **in exon 10 of 12**, so the transcript is predicted to undergo NMD.
- SpliceAI: **not assessed** — the release is built from a substitutions-only source, so it holds no insertion variants. That is a property of the dataset, not of the variant, and is not evidence against a splicing effect.
- Population frequency: **no gnomAD frequency available for this variant** — rarity (ACMG PM2) and BA1/BS1 cannot be assessed for this variant.

*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}

**WAS** population constraint: ClinGen dosage — haploinsufficiency 3/3, triplosensitivity 0/3. *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):

- **X-linked severe congenital neutropenia** — Definitive (XL)
- **Wiskott-Aldrich syndrome** — Definitive (XL)

## Protein context {#protein}

Residue **341** lies in the 'disordered' region.

AlphaFold model confidence (whole protein): pLDDT 70.84, 26% of residues very-high.

**7 experimental structure(s)** (PDB): [1CEE](https://www.rcsb.org/structure/1CEE), [1EJ5](https://www.rcsb.org/structure/1EJ5), [1T84](https://www.rcsb.org/structure/1T84), [2A3Z](https://www.rcsb.org/structure/2A3Z), [2K42](https://www.rcsb.org/structure/2K42), [2OT0](https://www.rcsb.org/structure/2OT0).

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

*Describes the biological roles of WAS (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:** WAS's established molecular role includes SH3 domain binding. p.Pro341fs falls in the disordered region. In Reactome, WAS is annotated in disease pathway(s) including **FCGR3A-mediated phagocytosis**.

**Disease mechanism (Reactome):** WAS loss or alteration is curated in [FCGR3A-mediated phagocytosis](https://reactome.org/content/detail/R-HSA-9664422).

### Pathways affected {#pathways}

WAS participates in **7 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [FCGR3A-mediated phagocytosis](https://reactome.org/content/detail/R-HSA-9664422) | electronic |
| [CDC42 GTPase cycle](https://reactome.org/content/detail/R-HSA-9013148) | curated |
| [Generation of second messenger molecules](https://reactome.org/content/detail/R-HSA-202433) | curated |
| [RAC1 GTPase cycle](https://reactome.org/content/detail/R-HSA-9013149) | curated |
| [RHOJ GTPase cycle](https://reactome.org/content/detail/R-HSA-9013409) | curated |
| [RHO GTPases Activate WASPs and WAVEs](https://reactome.org/content/detail/R-HSA-5663213) | electronic |
| [Regulation of actin dynamics for phagocytic cup formation](https://reactome.org/content/detail/R-HSA-2029482) | electronic |

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

**Molecular function:** SH3 domain binding, protein kinase binding, small GTPase binding, identical protein binding, phospholipase binding.

**Biological process:** regulation of T cell antigen processing and presentation, immune response, regulation of actin polymerization or depolymerization, regulation of lamellipodium assembly, actin filament polymerization, Cdc42 protein signal transduction.

## Clinical significance {#significance}

**Pathogenic** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2021-02-02.

**Submitter consensus:** unanimous (1/1 Pathogenic).

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Labcorp Genetics (formerly Invitae), Labcorp | Pathogenic | criteria provided, single submitter | clinical testing | 2021-02-02 |

## Associated conditions {#conditions}

[thrombocytopenia 1](https://sugi.bio/atlas/disease/thrombocytopenia-1/), [X-linked severe congenital neutropenia](https://sugi.bio/atlas/disease/x-linked-severe-congenital-neutropenia/), [Wiskott-Aldrich syndrome](https://sugi.bio/atlas/disease/wiskott-aldrich-syndrome/).

**Reported phenotype names (ClinVar):** Thrombocytopenia 1, Wiskott-Aldrich syndrome, X-linked severe congenital neutropenia, X-Linked Thrombocytopenia (XLT), THROMBOCYTOPENIA, X-LINKED, 1, X-linked thrombocytopenia with normal platelets, ALDRICH SYNDROME, IMMUNODEFICIENCY 2, WISKOTT-ALDRICH SYNDROME 1, Wiskott-aldrich syndrome, somatic.

## Similar variants {#similar}

Related WAS variant pages (same residue, condition, or type): [WAS p.Pro341Leu](/variant/was-p-pro341leu), [WAS p.Ile276fs](/variant/was-p-ile276fs), [WAS p.Leu105fs](/variant/was-p-leu105fs), [WAS p.Tyr102fs](/variant/was-p-tyr102fs), [WAS c.273+8_273+9insA](/variant/was-c-273-plus-8-273-plus-9insa), [WAS c.735-16_735-15insGT](/variant/was-c-735-minus-16-735-minus-15insgt), [WAS c.1339-2A>G](/variant/was-c-1339-minus-2a-g), [WAS c.1453+2T>C](/variant/was-c-1453-plus-2t-c).

### Data sources & attribution {#sources}

ClinVar (NCBI — public domain, built 2026-10-14); gnomAD v4.1 (Broad Institute, built 2026-10-14); 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 1418621). 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.*