CHRNA2

Chr 8AD

cholinergic receptor nicotinic alpha 2 subunit

NCBI Gene: 1135 ENSG00000120903 UniProt: Q15822

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels formed by a pentameric arrangement of alpha and beta subunits to create distinct muscle and neuronal receptors. Neuronal receptors are found throughout the peripheral and central nervous system where they are involved in fast synaptic transmission. This gene encodes an alpha subunit that is widely expressed in the brain. The proposed structure for nAChR subunits is a conserved N-terminal extracellular domain followed by three conserved transmembrane domains, a variable cytoplasmic loop, a fourth conserved transmembrane domain, and a short C-terminal extracellular region. Mutations in this gene cause autosomal dominant nocturnal frontal lobe epilepsy type 4. Single nucleotide polymorphisms (SNPs) in this gene have been associated with nicotine dependence. [provided by RefSeq, Nov 2009]

Primary Disease Associations & Inheritance

Epilepsy, nocturnal frontal lobe, type 4MIM #610353

UniProtSeizures, benign familial infantile, 6

599

ClinVar variants

Pathogenic / LP

0.00

pLI score

Active trials

Clinical Summary— CHRNA2

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Gene-Disease Validity (ClinGen)

sleep-related hypermotor epilepsy · ADLimited

Limited evidence — not for standalone diagnostic reporting

2 total gene-disease associations curated

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Population Constraint (gnomAD)

Low constraint (pLI 0.00) — loss-of-function variants are relatively tolerated in the population.

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ClinVar Variants

50 Pathogenic / Likely Pathogenic· 318 VUS of 599 total submissions

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Clinical Trials

1 active or recruiting trial — potential therapeutic options may be available

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

Tolerant — LoF & missense variants common in population

LoF Constraint?LOEUF (Loss-of-function Observed/Expected Upper bound Fraction) is the upper bound of the 90% CI for LoF OE — the preferred gnomAD v4 metric. Lower = more intolerant to LoF. LOEUF < 0.35 = highly constrained.

1.26LOEUF

pLI 0.000

Z-score 0.70

OE 0.83 (0.56–1.26)

Tolerant

Highly tolerant — LoF variants common in population

Missense Constraint?Missense Z-score: standard deviations fewer missense variants observed vs. expected. Z > 3.09 (p < 0.001) = gene does not tolerate missense variation. OE missense < 0.6 is also considered constrained.

-0.30Z-score

OE missense 1.05 (0.96–1.15)

334 obs / 318.9 exp

Tolerant

Tolerant to missense variation

Observed / Expected Ratios?Shaded band = 90% confidence interval. Vertical tick = point estimate. Grey threshold line = gnomAD constraint cutoff for that variant class.

LoF OE?Ratio of observed to expected LoF variants. Upper CI bound (LOEUF) ≤ 0.35 = strong LoF constraint signal.0.83 (0.56–1.26)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.1.05 (0.96–1.15)

0≤0.61.4

Synonymous OE?Control metric — synonymous variants are largely neutral and expected near OE = 1.0. Significant deviation may indicate annotation issues.1.06

0≤1.21.6

LoF obs/exp: 16 / 19.3Missense obs/exp: 334 / 318.9Syn Z: -0.54