Is CHRNA2 p.Ser116Arg (c.348C>A) pathogenic?

CHRNA2 p.Ser116Arg (c.348C>A) is classified Likely benign in CHRNA2 (ClinVar, Single submitter, 1 submitter; last evaluated 2022-10-17). AlphaMissense: likely benign (0.1895); Very rare (popmax 0.00268%, afr); Associated with familial sleep-related hypermotor epilepsy.

What condition is associated with CHRNA2 p.Ser116Arg (c.348C>A)?

CHRNA2 p.Ser116Arg (c.348C>A) is associated with familial sleep-related hypermotor epilepsy (ClinVar).

How common is CHRNA2 p.Ser116Arg (c.348C>A) in the general population?

CHRNA2 p.Ser116Arg (c.348C>A) is very rare (popmax 0.00268%, afr) (gnomAD).

How is Sleep-related hypermotor epilepsy inherited?

Typically Autosomal dominant (Orphanet). A genetic counselor can assess individual risk for a family.

What do computational predictors say about CHRNA2 p.Ser116Arg (c.348C>A)?

AlphaMissense predicts likely benign (score 0.1895) — an in-silico prediction, not a clinical call.

CHRNA2 p.Ser116Arg

c.348C>A · rs779790900 · VCV1644134

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.1895 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.00268%, afr)

Missense predictors

0/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

familial sleep-related hypermotor epilepsy

Computational evidence

Protein change
AlphaMissense	0.1895	likely benign
REVEL	0.072	moderately benign-leaning
SaProt	LLR -6.23	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 -5.7	GERP -3.9
Regional constraint	o/e 0.91	unconstrained · MANE · 7,404 bp · p 0.095 · regional, not allelic
Overall
CADD	1.09	PHRED · no single calibrated threshold — expert panels disagree

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

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00268% African / African-American · 2/74,710 alleles

Filtering AF 0.000502% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000367%

Overall 0.00087% 14/1,609,930 alleles · very rare

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.00268%	37,355
Remaining individualsnot grpmax-eligible	0.0016%	62,318
European (non-Finnish)	0.000935%	106,956

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: CHRNA2
Protein: p.Ser116Arg
Coding: c.348C>A
MANE Select: NM_000742
dbSNP: rs779790900
Type: single nucleotide variant
Location: chr8:27467330 (GRCh38)
Gene constraint: LOEUF 1.195 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 77.88 · 1 PDB
Residue 116: a β-strand

Full CHRNA2 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

familial sleep-related hypermotor epilepsy — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Sleep-related hypermotor epilepsy (Orphanet):

Inheritance: Autosomal dominant
Onset: Adolescent, Adult, Childhood

Similar variants

CHRNA2 p.Ser116Ile Benign/Likely benign ★★ same residue
CHRNA2 p.Ser116= Likely benign ★ same residue
CHRNA2 p.Ser116Gly Likely benign ★ ⚠ same residue
CHRNA2 c.1464+4C>T Uncertain significance ★★ same condition
CHRNA2 c.1464+5G>A Uncertain significance ★★ same condition
CHRNA2 c.294+1G>A Uncertain significance ★★ same condition
CHRNA2 c.294+5G>A Uncertain significance ★★ same condition
CHRNA2 c.449+3A>T Uncertain significance ★★ same condition

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/chrna2-p-ser116arg (accessed [today's date]).

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