Is CNP p.Ala218Val (c.653C>T) pathogenic?

CNP p.Ala218Val (c.653C>T) is classified Uncertain significance in CNP (ClinVar, Single submitter, 1 submitter; last evaluated 2025-04-11). AlphaMissense: likely benign (0.1188); Ultra-rare (popmax 0.0589%, afr).

How common is CNP p.Ala218Val (c.653C>T) in the general population?

CNP p.Ala218Val (c.653C>T) is ultra-rare (popmax 0.0589%, afr) (gnomAD).

What do computational predictors say about CNP p.Ala218Val (c.653C>T)?

AlphaMissense predicts likely benign (score 0.1188) — an in-silico prediction, not a clinical call.

CNP p.Ala218Val

c.653C>T · VCV4004401

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.1188 · ACMG-weighted

gnomAD v4.1

Rare

ultra-rare (popmax 0.0589%, afr)

Missense predictors

0/3 damaging

AlphaMissense, REVEL, SaProt

Computational evidence

Protein change
AlphaMissense	0.1188	likely benign
REVEL	0.16	moderately benign-leaning
SaProt	LLR -6.70	tolerated
⇒ AlphaMissense, REVEL and SaProt all call this tolerated.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 4.8	GERP 2.4, phastCons 1
Regional constraint	o/e 1.00	unconstrained · MANE · 5,251 bp · p 0.97 · regional, not allelic
Overall
CADD	22.2	PHRED · no single calibrated threshold — expert panels disagree

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

AlphaMissense carries the ACMG weight for missense; REVEL and SaProt are independent agreement signals.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0589% African / African-American · 44/74,762 alleles

Filtering AF 0.045% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.0402%

Overall 0.00385% 62/1,611,192 alleles · ultra-rare

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.0589%	1,699
Remaining individualsnot grpmax-eligible	0.00481%	20,783
European (non-Finnish)	0.00127%	78,543

Rarity supports pathogenicity (ACMG PM2); frequency above a disease-specific BA1/BS1 threshold argues against it. A variant frequent in one ancestry group can be near-absent in others, so a single global figure can mislead.

Variant & gene context

Gene: CNP
Protein: p.Ala218Val
Coding: c.653C>T
MANE Select: NM_033133
Type: single nucleotide variant
Location: chr17:41968717 (GRCh38)
Gene constraint: LOEUF 0.379 · pLI 1.00 (gnomAD)
Structure: AlphaFold pLDDT 87.54 · 1 PDB
Residue 218: an α-helix

Full CNP gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Similar variants

CNP p.Arg353Trp Uncertain significance ★★ ⚠ same type
CNP p.Gly365= Benign ★★ same type
CNP p.Ala269Val Uncertain significance ★ ⚠ same type
CNP p.Ala281Val Uncertain significance ★ ⚠ same type
CNP p.Ala92Thr Uncertain significance ★ ⚠ same type
CNP p.Arg114Gln Uncertain significance ★ ⚠ same type
CNP p.Arg128Gln Uncertain significance ★ ⚠ same type
CNP p.Arg203Cys Uncertain significance ★ ⚠ same type

Built on 18 open, versioned datasets — ClinVar, gnomAD, AlphaMissense, REVEL, ClinGen & more — plus Sugi Variant's own cross-source analysis. Source data 2026-01–2026-10, ClinVar 2026-10. Full sources & versions →

Cite Sugi Variant

Gür T. Sugi Variant: A Deterministic Per-Variant Germline Reference from a Knowledge Graph for Humans and AI Agents. 2026. doi:10.5281/zenodo.21509445. This variant: https://sugi.bio/variant/cnp-p-ala218val (accessed [today's date]).

Preprint & method: sugi.bio/variant/method Machine-readable: this page as Markdown