Is OTC p.Ser321Ter (c.962C>A) pathogenic?

OTC p.Ser321Ter (c.962C>A) is classified Pathogenic in OTC (ClinVar, Single submitter, 2 submitters; last evaluated 2025-05-28). Absent from gnomAD v4.1; Associated with ornithine carbamoyltransferase deficiency.

What condition is associated with OTC p.Ser321Ter (c.962C>A)?

OTC p.Ser321Ter (c.962C>A) is associated with ornithine carbamoyltransferase deficiency (ClinVar).

How common is OTC p.Ser321Ter (c.962C>A) in the general population?

OTC p.Ser321Ter (c.962C>A) is absent from gnomAD v4.1 (gnomAD).

How is Ornithine transcarbamylase deficiency inherited?

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

OTC p.Ser321Ter

c.962C>A · rs72558475 · VCV97373

Pathogenic Single submitter

Classification

Pathogenic

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 2 submitters

Consequence

nonsense (stop-gain)

predicted LoF

gnomAD v4.1

Absent

absent from gnomAD v4.1

Conditions

ornithine carbamoyltransferase deficiency

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 in a haploinsufficient gene (ClinGen)
NMD	escapes	premature termination codon within the last 50 nt of the penultimate exon (9 of 10, 43 nt from its 3' end) — the truncated protein is likely expressed. PVS1 input, not an applied code
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 7.6	GERP 2.2, phastCons 1
Overall
CADD	36.0	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

Absent from gnomAD v4.1. Not observed in any sequenced alleles — a rarity signal (ACMG PM2-supporting), not evidence of pathogenicity on its own.

Variant & gene context

Gene: OTC
Protein: p.Ser321Ter
Coding: c.962C>A
MANE Select: NM_000531
dbSNP: rs72558475
Type: single nucleotide variant
Location: chrX:38411956 (GRCh38)
Structure: AlphaFold pLDDT 91.94 · 4 PDB

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

Disease context

ornithine carbamoyltransferase deficiency — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Ornithine transcarbamylase deficiency (Orphanet):

Inheritance: X-linked recessive
Onset: All ages
Prevalence: 1-9 / 100 000 (Europe)

Similar variants

OTC p.Ser321= Likely benign ★★ same residue
OTC p.Ser321Pro Likely pathogenic ★ same residue
OTC p.Ser321Leu Likely pathogenic ★ same residue
OTC c.298+2T>G Pathogenic ★★ same condition
OTC c.299-1G>A Likely pathogenic ★★ same condition
OTC c.386+1G>A Pathogenic ★★ same condition
OTC c.540+1G>A Pathogenic ★★ same condition
OTC c.540+1G>T 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/otc-p-ser321ter (accessed [today's date]).

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