# NM_000530.8(MPZ):c.65_66insAG (p.Val23fs)

https://sugi.bio/variant/mpz-p-val23fs

## Summary

**MPZ p.Val23fs (c.65_66insAG)** is classified **Pathogenic** in MPZ (ClinVar, Single submitter, 1 submitter; last evaluated 2025-07-15). Associated with Charcot-Marie-Tooth disease type 1.

**At a glance:** Pathogenic · review: Single submitter · 1 submitter · 1 linked condition

## For patients & families {#patients}

This is a change in the MPZ gene that is reported as disease-causing, but on limited review, submitted by 1 submitter, and is linked to Charcot-Marie-Tooth disease type 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.*

**Support & next steps:** [Condition overview & support (NIH GARD)](https://rarediseases.info.nih.gov/diseases/0012433/index) · [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [MPZ](https://sugi.bio/atlas/gene/MPZ/) |
| Protein change (HGVS p.) | p.Val23fs |
| Coding change (HGVS c.) | c.65_66insAG |
| MANE Select transcript | [NM_000530](https://www.ncbi.nlm.nih.gov/nuccore/NM_000530) |
| Variant type | Insertion |
| Location | chr1:161309840-161309841 (GRCh38) |
| ClinVar | [VCV4723275](https://www.ncbi.nlm.nih.gov/clinvar/variation/4723275/) |

**All HGVS expressions:** `LRG_256:g.5132_5133insAG`, `LRG_256t1:c.65_66insAG`, `LRG_317:g.465_466insCT`, `NC_000001.10:g.161279630_161279631insCT`, `NC_000001.11:g.161309840_161309841insCT`, `NG_008055.1:g.5132_5133insAG`, `NG_012767.1:g.465_466insCT`, `NM_000530.8:c.65_66insAG`, `NM_001315491.2:c.65_66insAG`

## 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 1.806, GERP 1.37, phastCons 1 — weakly conserved position
- Molecular consequence: **frameshift** — a predicted loss-of-function variant. Gene population constraint: LOEUF 0.708, pLI 0.11226. *Descriptive; not an applied PVS1 code.*
- Nonsense-mediated decay: the premature termination codon is **in exon 1 of 6**, 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.

*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}

**MPZ** population constraint: LOEUF 0.708, pLI 0.11226, missense-Z 1.4841; ClinGen dosage — haploinsufficiency 2/3, triplosensitivity 1/3. *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):

- **Charcot-Marie-Tooth disease** — Definitive (AD)

## Protein context {#protein}


AlphaFold model confidence (whole protein): pLDDT 82.38, 57% of residues very-high.

**2 experimental structure(s)** (PDB): [3OAI](https://www.rcsb.org/structure/3OAI), [8IIA](https://www.rcsb.org/structure/8IIA).

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

*Describes the biological roles of MPZ (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.*


### Pathways affected {#pathways}

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

| Pathway (Reactome) | Evidence |
| --- | --- |
| [EGR2 and SOX10-mediated initiation of Schwann cell myelination](https://reactome.org/content/detail/R-HSA-9619665) | curated |

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

**Biological process:** myelination, cell-cell adhesion, cell aggregation.

## Clinical significance {#significance}

**Pathogenic** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2025-07-15.

**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 | 2025-07-15 |

## Associated conditions {#conditions}

[Charcot-Marie-Tooth disease type 1](https://sugi.bio/atlas/disease/charcot-marie-tooth-disease-type-1/).

**Reported phenotype names (ClinVar):** Charcot-Marie-Tooth disease, type I, Charcot-Marie-Tooth, Type 1, Charcot-Marie-Tooth disease type 1.

## Similar variants {#similar}

Related MPZ variant pages (same residue, condition, or type): [MPZ p.Val23Met](/variant/mpz-p-val23met), [MPZ p.Val102fs](/variant/mpz-p-val102fs), [MPZ c.235-1G>T](/variant/mpz-c-235-minus-1g-t), [MPZ c.448+1G>A](/variant/mpz-c-448-plus-1g-a), [MPZ c.448+1G>T](/variant/mpz-c-448-plus-1g-t), [MPZ c.448+2T>G](/variant/mpz-c-448-plus-2t-g), [MPZ c.584+2T>G](/variant/mpz-c-584-plus-2t-g), [MPZ c.68-1G>A](/variant/mpz-c-68-minus-1g-a).

### Data sources & attribution {#sources}

ClinVar (NCBI — public domain, built 2026-10-14); gnomAD v4.1 (Broad Institute, built 2026-10-15); 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 4723275). 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.*