# NM_001386140.1(MTTP):c.1226_1227delinsTT (p.Arg409Ile)

https://sugi.bio/variant/mttp-p-arg409ile

## Summary

**MTTP p.Arg409Ile (c.1226_1227delinsTT)** is classified **Uncertain significance** in MTTP (ClinVar, Single submitter, 1 submitter; last evaluated 2021-08-18). No gnomAD frequency available for this variant.

**At a glance:** Uncertain significance · review: Single submitter · rsID rs2110224707 · 1 submitter · no gnomAD frequency available for this variant

## For patients & families {#patients}

This is a change in the MTTP gene that is currently of uncertain significance — a definitive interpretation has not yet been established, submitted by 1 submitter.

*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 | [MTTP](https://sugi.bio/atlas/gene/MTTP/) |
| Protein change (HGVS p.) | p.Arg409Ile |
| Coding change (HGVS c.) | c.1226_1227delinsTT |
| MANE Select transcript | [NM_001386140](https://www.ncbi.nlm.nih.gov/nuccore/NM_001386140) |
| dbSNP | [rs2110224707](https://www.ncbi.nlm.nih.gov/snp/rs2110224707/) |
| Variant type | Indel |
| Location | chr4:99600723-99600724 (GRCh38) |
| ClinVar | [VCV1412047](https://www.ncbi.nlm.nih.gov/clinvar/variation/1412047/) |

**All HGVS expressions:** `NC_000004.11:g.100521880_100521881delinsTT`, `NC_000004.12:g.99600723_99600724delinsTT`, `NG_011469.1:g.41641_41642delinsTT`, `NM_000253.4:c.1226_1227delinsTT`, `NM_001300785.2:c.977_978delinsTT`, `NM_001386140.1:c.1226_1227delinsTT`

## 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 4.781, GERP -1.04, phastCons 1 — highly conserved position (PP3-type support)
- Regional missense constraint: **o/e 0.89** across the covering region of the MANE Select transcript (99,574,910–99,622,845), spanning 47,935 bp. Chi-square p 0.00018. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI: **not assessed** — the release is built from a substitutions-only source, so it holds no indel 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}

**MTTP** population constraint: LOEUF 0.672, pLI 6.7227e-07, missense-Z 1.9465; ClinGen dosage — haploinsufficiency gene assoc. with recessive phenotype, triplosensitivity 0/3. *Lower LOEUF and higher pLI indicate a gene that tolerates loss-of-function poorly; ClinGen dosage is the curated haploinsufficiency call.*

## Protein context {#protein}

Residue **409** lies in the vitellogenin domain; an α-helix.

AlphaFold model confidence (whole protein): pLDDT 86.73, 56% of residues very-high.

**2 experimental structure(s)** (PDB): [6I7S](https://www.rcsb.org/structure/6I7S), [8EOJ](https://www.rcsb.org/structure/8EOJ).

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

*Describes the biological roles of MTTP (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:** MTTP's established molecular role includes protein heterodimerization activity. p.Arg409Ile falls in the vitellogenin domain.


### Pathways affected {#pathways}

MTTP participates in **3 Reactome pathways** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| [Chylomicron assembly](https://reactome.org/content/detail/R-HSA-8963888) | curated |
| [LDL remodeling](https://reactome.org/content/detail/R-HSA-8964041) | curated |
| [VLDL assembly](https://reactome.org/content/detail/R-HSA-8866423) | curated |

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

**Molecular function:** protein heterodimerization activity, phospholipid transfer activity, phosphatidylcholine transfer activity, cholesterol transfer activity, triglyceride transfer activity, ceramide 1-phosphate transfer activity.

**Biological process:** protein secretion, phospholipid transport, triglyceride transport, plasma lipoprotein particle assembly.

## Clinical significance {#significance}

**Uncertain significance** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2021-08-18.

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

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Labcorp Genetics (formerly Invitae), Labcorp | Uncertain significance | criteria provided, single submitter | clinical testing | 2021-08-18 |

**Reported phenotype names (ClinVar):** not provided, none provided, RECLASSIFIED - ADRA2C POLYMORPHISM, RECLASSIFIED - ADRB1 POLYMORPHISM.

## Similar variants {#similar}

Related MTTP variant pages (same residue, condition, or type): [MTTP p.Gly444Asp](/variant/mttp-p-gly444asp), [MTTP p.Ala410fs](/variant/mttp-p-ala410fs), [MTTP p.Ala758fs](/variant/mttp-p-ala758fs), [MTTP p.Asn237delinsArgCysValTer](/variant/mttp-p-asn237delinsargcysvalter), [MTTP p.Asn685fs](/variant/mttp-p-asn685fs), [MTTP p.Gly163fs](/variant/mttp-p-gly163fs), [MTTP p.Phe767fs](/variant/mttp-p-phe767fs), [MTTP p.Thr245fs](/variant/mttp-p-thr245fs).

### 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 1412047). 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.*