# NM_001128178.3(NPHP1):c.764T>C (p.Ile255Thr)

https://sugi.bio/variant/nphp1-p-ile255thr

## Summary

**NPHP1 p.Ile255Thr (c.764T>C)** is classified **Uncertain significance** in NPHP1 (ClinVar, Single submitter, 1 submitter; last evaluated 2025-10-07). AlphaMissense: likely benign (0.2386); Absent from gnomAD v4.1; Associated with Inborn genetic diseases.

**At a glance:** Uncertain significance · review: Single submitter · 1 submitter · 1 linked condition · AlphaMissense likely benign · absent from gnomAD v4.1

## For patients & families {#patients}

This is a change in the NPHP1 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 | [NPHP1](https://sugi.bio/atlas/gene/NPHP1/) |
| Protein change (HGVS p.) | p.Ile255Thr |
| Coding change (HGVS c.) | c.764T>C |
| MANE Select transcript | [NM_001128178](https://www.ncbi.nlm.nih.gov/nuccore/NM_001128178) |
| Variant type | single nucleotide variant |
| Location | chr2:110164695-110164695 (GRCh38) |
| ClinVar | [VCV4626323](https://www.ncbi.nlm.nih.gov/clinvar/variation/4626323/) |

**All HGVS expressions:** `NC_000002.11:g.110922272A>G`, `NC_000002.12:g.110164695A>G`, `NG_008287.1:g.45368T>C`, `NM_000272.5:c.764T>C`, `NM_001128178.3:c.764T>C`, `NM_001128179.3:c.578T>C`, `NM_001374256.1:c.764T>C`, `NM_001374257.1:c.764T>C`, `NM_207181.4:c.764T>C`

## Computational & population evidence {#evidence}

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

- AlphaMissense **likely benign** (0.2386)
- REVEL 0.336 (indeterminate)
- SaProt LLR -6.869 (tolerated) — agrees with AlphaMissense
- → **In-silico consensus:** AlphaMissense and SaProt both call this tolerated; REVEL is indeterminate
- SpliceAI predicts **acceptor gain** (Δ 0.20) — a splice-altering prediction on an uncertain variant — a signal for review
- Conservation: phyloP 9.131, GERP 1.18, phastCons 1 — highly conserved (differs from AlphaMissense)
- CADD: **PHRED 22.2**. 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 0.96** across the covering region of the MANE Select transcript (110,123,794–110,204,968), spanning 81,174 bp. Chi-square p 0.26. 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 **0.00**, acceptor gain **0.20**, donor gain **0.02**. Largest is acceptor gain.
- SpliceAI deltas (masked): acceptor loss **0.00**, donor loss **0.00**, acceptor gain **0.20**, donor gain **0.02**.
- Population frequency: **absent from gnomAD v4.1** — a rarity signal (ACMG PM2-supporting), not evidence of pathogenicity on its own.

*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}

**NPHP1** population constraint: LOEUF 0.92, pLI 4.482e-10, missense-Z 0.65749. *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):

- **nephronophthisis 1** — Definitive (AR)

## Protein context {#protein}


AlphaFold model confidence (whole protein): pLDDT 76.22, 45% of residues very-high.

**2 experimental structure(s)** (PDB): [1S1N](https://www.rcsb.org/structure/1S1N), [6O1Q](https://www.rcsb.org/structure/6O1Q).

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

*Describes the biological roles of NPHP1 (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}

NPHP1 participates in **1 Reactome pathway** (⚕ = disease pathway):

| Pathway (Reactome) | Evidence |
| --- | --- |
| [Anchoring of the basal body to the plasma membrane](https://reactome.org/content/detail/R-HSA-5620912) | curated |

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

**Biological process:** positive regulation of bicellular tight junction assembly.

## Clinical significance {#significance}

**Uncertain significance** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2025-10-07.

**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 | 2025-10-07 |

## 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 NPHP1 variant pages (same residue, condition, or type): [NPHP1 p.Gly287Arg](/variant/nphp1-p-gly287arg), [NPHP1 c.771+136C>A](/variant/nphp1-c-771-plus-136c-a), [NPHP1 c.771+26A>G](/variant/nphp1-c-771-plus-26a-g), [NPHP1 c.771+38G>T](/variant/nphp1-c-771-plus-38g-t), [NPHP1 p.Arg389His](/variant/nphp1-p-arg389his), [NPHP1 p.Arg628Gln](/variant/nphp1-p-arg628gln), [NPHP1 p.Asn59His](/variant/nphp1-p-asn59his), [NPHP1 p.Asp569Val](/variant/nphp1-p-asp569val).

### 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 4626323). 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.*