# NM_006662.3(SRCAP):c.2818C>T (p.Arg940Trp)

https://sugi.bio/variant/srcap-p-arg940trp

## Summary

**SRCAP p.Arg940Trp (c.2818C>T)** is classified **Uncertain significance** in SRCAP (ClinVar, Single submitter, 1 submitter; last evaluated 2024-06-22). AlphaMissense: likely benign (0.2789); Very rare (popmax 0.00111%, sas); Associated with developmental delay, hypotonia, musculoskeletal defects, and behavioral abnormalities.

**At a glance:** Uncertain significance · review: Single submitter · 1 submitter · 2 linked conditions · AlphaMissense likely benign · very rare (popmax 0.00111%, sas)

## For patients & families {#patients}

This is a change in the SRCAP gene that is currently of uncertain significance — a definitive interpretation has not yet been established, submitted by 1 submitter, and is linked to developmental delay, hypotonia, musculoskeletal defects, and behavioral abnormalities.

*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 | [SRCAP](https://sugi.bio/atlas/gene/SRCAP/) |
| Protein change (HGVS p.) | p.Arg940Trp |
| Coding change (HGVS c.) | c.2818C>T |
| MANE Select transcript | [NM_006662](https://www.ncbi.nlm.nih.gov/nuccore/NM_006662) |
| Variant type | single nucleotide variant |
| Location | chr16:30720162-30720162 (GRCh38) |
| ClinVar | [VCV3580100](https://www.ncbi.nlm.nih.gov/clinvar/variation/3580100/) |

**All HGVS expressions:** `NC_000016.10:g.30720162C>T`, `NC_000016.9:g.30731483C>T`, `NG_032135.1:g.26022C>T`, `NG_032135.2:g.25993C>T`, `NM_006662.3:c.2818C>T`

## Computational & population evidence {#evidence}

**Concordance:** Mixed / partial computational evidence (see below).

- AlphaMissense **likely benign** (0.2789)
- REVEL 0.61 (indeterminate)
- Conservation: phyloP 2.787, GERP 0.723, phastCons 1 — highly conserved (differs from AlphaMissense)
- **SaProt:** not scored — SaProt is structure-aware and AlphaFold DB has no model for this protein. That is a property of the dataset, not of the variant, and is not evidence either way.
- CADD: **PHRED 25.7**. 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 0.69** across the covering region of the MANE Select transcript (30,716,115–30,720,723), spanning 4,608 bp. Chi-square p 6.7e-06. Describes the region, not this allele; gnomAD v4.1.1's own constrained determination. *Descriptive; no ACMG code applied.*
- SpliceAI: **below the reporting threshold**. This position is scored for a different substitution (C>G, Δ0.24 acceptor loss), so this allele was evaluated and its deltas all fell under Δ0.2 — a prediction of no splicing effect for this allele, not a gap in our data. *No ACMG code assigned.*
- Population frequency (gnomAD v4.1): grpmax **0.00111%** (sas) · 1/90,464 in the highest group · 5/1,599,424 alleles overall — very rare (popmax 0.00111%, sas).

| Ancestry group | Allele frequency | 1 in |
| --- | --- | --- |
| Remaining individuals (not grpmax-eligible) | 0.00485% | 20,629 |
| South Asian (grpmax) | 0.00111% | 90,464 |
| European (non-Finnish) | 8.56e-05% | 1,168,344 |

Remaining individuals shows a higher raw frequency than the grpmax group. gnomAD excludes bottlenecked groups — Finnish, Ashkenazi Jewish, Amish and "Remaining individuals" — from grpmax, because founder effects make their frequencies unrepresentative for filtering. The table is sorted by frequency, so an excluded group can sit above the grpmax row.

*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}

**SRCAP** population constraint: LOEUF 0.223, pLI 1, missense-Z 3.6475; 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):

- **Floating-Harbor syndrome** — Definitive (AD)

## Protein context {#protein}

Residue **940** lies in a UniProt-annotated variant site (in dehmba).

**22 experimental structure(s)** (PDB): [6IGM](https://www.rcsb.org/structure/6IGM), [8X15](https://www.rcsb.org/structure/8X15), [8X19](https://www.rcsb.org/structure/8X19), [8X1C](https://www.rcsb.org/structure/8X1C), [9CA7](https://www.rcsb.org/structure/9CA7), [9CA8](https://www.rcsb.org/structure/9CA8) — incl. mutant structure 9UBD.

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

*Describes the biological roles of SRCAP (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:** SRCAP's established molecular role includes transcription coactivator activity.


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

**Molecular function:** transcription coactivator activity, ATP-dependent chromatin remodeler activity.

**Biological process:** positive regulation of transcription by RNA polymerase II, cAMP/PKA signal transduction.

## Clinical significance {#significance}

**Uncertain significance** — review status Single submitter *(criteria provided, single submitter)*, last evaluated 2024-06-22.

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

### Submitter classifications {#submitters}

| Submitter | Classification | Review | Method | Date |
| --- | --- | --- | --- | --- |
| Fulgent Genetics, Fulgent Genetics | Uncertain significance | criteria provided, single submitter | clinical testing | 2024-06-22 |

## Associated conditions {#conditions}

[developmental delay, hypotonia, musculoskeletal defects, and behavioral abnormalities](https://sugi.bio/atlas/disease/developmental-delay-hypotonia-musculoskeletal-defects-and-behavioral-abnormalities/), [Floating-Harbor syndrome](https://sugi.bio/atlas/disease/floating-harbor-syndrome/).

**Reported phenotype names (ClinVar):** Developmental delay, hypotonia, musculoskeletal defects, and behavioral abnormalities, Floating-Harbor syndrome, SRCAP-Related Floating-Harbor Syndrome, Short stature with delayed bone age, expressive language delay, a triangular face with a prominent nose and deep-set eyes, Pelletier-Leisti syndrome.

## Similar variants {#similar}

Related SRCAP variant pages (same residue, condition, or type): [SRCAP p.Arg940Gln](/variant/srcap-p-arg940gln), [SRCAP p.Arg2329Ter](/variant/srcap-p-arg2329ter), [SRCAP p.Arg2435Ter](/variant/srcap-p-arg2435ter), [SRCAP p.Arg2444Ter](/variant/srcap-p-arg2444ter), [SRCAP p.Arg2718Ter](/variant/srcap-p-arg2718ter), [SRCAP p.Arg2748Ter](/variant/srcap-p-arg2748ter), [SRCAP p.Gln2407Ter](/variant/srcap-p-gln2407ter), [SRCAP p.Gln2419Ter](/variant/srcap-p-gln2419ter).

### 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 3580100). 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.*