# NM_002435.3(MPI):c.256G>A (p.Val86Ile)

https://sugi.bio/variant/mpi-p-val86ile

## Summary

**MPI p.Val86Ile (c.256G>A)** is classified **Uncertain significance** in MPI (ClinVar, Single submitter, 1 submitter; last evaluated 2025-02-07). AlphaMissense: likely benign (0.1359); Ultra-rare (popmax 0.0107%, afr); Associated with Inborn genetic diseases.

**At a glance:** Uncertain significance · review: Single submitter · 1 submitter · 1 linked condition · AlphaMissense likely benign · ultra-rare (popmax 0.0107%, afr)

## For patients & families {#patients}

This is a change in the MPI gene that is currently of uncertain significance — a definitive interpretation has not yet been established, submitted by 1 submitter, and is linked to Inborn genetic diseases.

*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:** [Find a genetic counselor (NSGC)](https://findageneticcounselor.nsgc.org/).

## Identity {#identity}

| Field | Value |
| --- | --- |
| Gene | [MPI](https://sugi.bio/atlas/gene/MPI/) |
| Protein change (HGVS p.) | p.Val86Ile |
| Coding change (HGVS c.) | c.256G>A |
| MANE Select transcript | [NM_002435](https://www.ncbi.nlm.nih.gov/nuccore/NM_002435) |
| Variant type | single nucleotide variant |
| Location | chr15:74891490-74891490 (GRCh38) |
| ClinVar | [VCV3874169](https://www.ncbi.nlm.nih.gov/clinvar/variation/3874169/) |

**All HGVS expressions:** `NC_000015.10:g.74891490G>A`, `NC_000015.9:g.75183831G>A`, `NG_008921.1:g.6422G>A`, `NG_008921.2:g.6450G>A`, `NM_001289155.2:c.256G>A`, `NM_001289156.2:c.106G>A`, `NM_001289157.2:c.256G>A`, `NM_001330372.2:c.196G>A`, `NM_002435.3:c.256G>A`

## Computational & population evidence {#evidence}

**Concordance:** ClinVar classifies this **uncertain**; the computational predictors unanimously lean **tolerated** — a triage signal, not a reclassification.

- AlphaMissense **likely benign** (0.1359)
- REVEL 0.571 (indeterminate)
- SaProt LLR -8.136 (tolerated) — agrees with AlphaMissense
- → **In-silico consensus:** AlphaMissense and SaProt both call this tolerated; REVEL makes no call
- SpliceAI predicts **donor loss** (Δ 0.24) — a splice-altering prediction on an uncertain variant — a signal for review
- Conservation: phyloP 8.646, GERP 1.98, phastCons 1 — highly conserved (differs from AlphaMissense)
- CADD: **PHRED 23.4**. 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 0.98** across the covering region of the MANE Select transcript (74,890,074–74,897,727), spanning 7,653 bp. Chi-square p 0.66. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI deltas (raw): acceptor loss **0.00**, donor loss **0.24**, acceptor gain **0.00**, donor gain **0.00**. Largest is donor loss, 1 bp away.
- SpliceAI deltas (masked): acceptor loss **0.00**, donor loss **0.00**, acceptor gain **0.00**, donor gain **0.00**.
  Masked SpliceAI — what Ensembl VEP and the Broad lookup serve by default — is below the reporting threshold here, so those tools show **no splice signal** for this allele. Masking zeroes a loss scored against a position that is not an annotated splice site, and a gain that merely strengthens an existing one, so the raw score above is describing a cryptic site rather than the site the variant sits on. *No ACMG code is assigned either way.*
- Population frequency (gnomAD v4.1): grpmax **0.0107%** (afr) · FAF95 0.00528% · FAF99 0.00381% · 8/74,926 in the highest group · 10/1,614,080 alleles overall — ultra-rare (popmax 0.0107%, afr).

| Ancestry group | Allele frequency | 1 in |
| --- | --- | --- |
| African / African-American (grpmax) | 0.0107% | 9,366 |
| European (non-Finnish) | 0.000169% | 590,023 |

*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}

**MPI** population constraint: LOEUF 1.04, pLI 9.3378e-10, missense-Z 0.59212. *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):

- **MPI-congenital disorder of glycosylation** — Definitive (AR)

## Protein context {#protein}


AlphaFold model confidence (whole protein): pLDDT 96.50, 97% of residues very-high.

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

*Describes the biological roles of MPI (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:** MPI's established molecular role includes mannose-6-phosphate isomerase activity. In Reactome, MPI is annotated in disease pathway(s) including **Defective MPI causes MPI-CDG**.

**Disease mechanism (Reactome):** MPI loss or alteration is curated in [Defective MPI causes MPI-CDG](https://reactome.org/content/detail/R-HSA-4043916).

### Pathways affected {#pathways}

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

| Pathway (Reactome) | Evidence |
| --- | --- |
| ⚕ [Defective MPI causes MPI-CDG](https://reactome.org/content/detail/R-HSA-4043916) | curated |
| [Synthesis of GDP-mannose](https://reactome.org/content/detail/R-HSA-446205) | curated |

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

**Molecular function:** mannose-6-phosphate isomerase activity.

**Biological process:** mannose to fructose-6-phosphate catabolic process, obsolete GDP-D-mannose biosynthetic process from fructose-6-phosphate.

## Clinical significance {#significance}

**Uncertain significance** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2025-02-07.

**Submitter consensus:** unanimous (1/1 Uncertain significance).

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Ambry Genetics | Uncertain significance | criteria provided, single submitter | clinical testing | 2025-02-07 |

## Associated conditions {#conditions}

[Inborn genetic diseases](https://sugi.bio/atlas/disease/inborn-genetic-diseases/).

**Reported phenotype names (ClinVar):** Inborn genetic diseases.

## Similar variants {#similar}

Related MPI variant pages (same residue, condition, or type): [MPI p.Val86=](/variant/mpi-p-val86), [MPI p.Asn273Ser](/variant/mpi-p-asn273ser), [MPI p.Asp80Asn](/variant/mpi-p-asp80asn), [MPI p.Glu331Ala](/variant/mpi-p-glu331ala), [MPI p.Lys360Arg](/variant/mpi-p-lys360arg), [MPI p.Pro326Ser](/variant/mpi-p-pro326ser), [MPI p.Thr177Ile](/variant/mpi-p-thr177ile), [MPI p.Val158Ile](/variant/mpi-p-val158ile).

### Data sources & attribution {#sources}

ClinVar (NCBI — public domain, built 2026-10-14); 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 3874169). 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.*