Is ASNS p.Arg63Ter (c.187C>T) pathogenic?

ASNS p.Arg63Ter (c.187C>T) is classified Pathogenic/Likely pathogenic in ASNS (ClinVar, Multiple submitters, 5 submitters; last evaluated 2025-12-02). Very rare (popmax 0.00133%, afr); Associated with congenital microcephaly - severe encephalopathy - progressive cerebral atrophy syndrome.

How common is ASNS p.Arg63Ter (c.187C>T) in the general population?

ASNS p.Arg63Ter (c.187C>T) is very rare (popmax 0.00133%, afr) (gnomAD).

ASNS p.Arg63Ter

Q: What condition is associated with ASNS p.Arg63Ter (c.187C>T)?

ASNS p.Arg63Ter (c.187C>T) is associated with congenital microcephaly - severe encephalopathy - progressive cerebral atrophy syndrome (ClinVar).

Q: How is Congenital microcephaly-severe encephalopathy-progressive cerebral atrophy syndrome inherited?

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

c.187C>T · rs373645939 · VCV421213

Pathogenic/Likely pathogenic Multiple submitters

Classification

Pathogenic/Likely pathogenic

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 5 submitters

Consequence

nonsense (stop-gain)

predicted LoF

gnomAD v4.1

Rare

very rare (popmax 0.00133%, afr)

Conditions

congenital microcephaly - severe encephalopathy - progressive cerebral atrophy syndrome

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Consequence	nonsense (stop-gain)	predicted loss-of-function
NMD	predicted	premature termination codon in exon 3 of 13
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 3.5	GERP -0.086, phastCons 1
Overall
CADD	37.0	PHRED · no single calibrated threshold — expert panels disagree

Predicted loss-of-function is descriptive, not an applied PVS1 code.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00133% African / African-American · 1/74,924 alleles

Filtering AF 0.000688% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000539%

Overall 0.000991% 16/1,614,040 alleles · very rare

Ancestry group	Frequency	1 in
Remaining individualsnot grpmax-eligible	0.0016%	62,490
African / African-Americangrpmax	0.00133%	74,924
European (non-Finnish)	0.00119%	84,289

Remaining individuals shows a higher raw frequency than the grpmax group above it. 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.

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: ASNS
Protein: p.Arg63Ter
Coding: c.187C>T
MANE Select: NM_001673
dbSNP: rs373645939
Type: single nucleotide variant
Location: chr7:97868970 (GRCh38)
Gene constraint: LOEUF 0.745 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 94.36 · 3 PDB
Residue 63: the glutamine amidotransferase type-2 domain

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

Disease context

congenital microcephaly - severe encephalopathy - progressive cerebral atrophy syndrome — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Congenital microcephaly-severe encephalopathy-progressive cerebral atrophy syndrome (Orphanet):

Inheritance: Autosomal recessive
Onset: Infancy, Neonatal

Similar variants

ASNS p.Arg63Gln Uncertain significance ★ ⚠ same residue
ASNS c.1030+1G>A Likely pathogenic ★★ same condition
ASNS c.1138-1G>A Likely pathogenic ★★ same condition
ASNS c.1239-2A>T Likely pathogenic ★★ same condition
ASNS c.1320+1G>C Likely pathogenic ★★ same condition
ASNS c.1320+1G>T Likely pathogenic ★★ same condition
ASNS c.1321-1G>A Likely pathogenic ★★ same condition
ASNS c.1476+1G>A Pathogenic ★★ 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/asns-p-arg63ter (accessed [today's date]).

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