Is MCCC2 p.Arg327Gly (c.979A>G) pathogenic?

MCCC2 p.Arg327Gly (c.979A>G) is classified Uncertain significance in MCCC2 (ClinVar, No assertion criteria, 1 submitter; last evaluated 2025-03-31). AlphaMissense: likely benign (0.2026); Very rare (popmax 0.000254%, nfe); Associated with 3-methylcrotonyl-CoA carboxylase 2 deficiency.

What condition is associated with MCCC2 p.Arg327Gly (c.979A>G)?

MCCC2 p.Arg327Gly (c.979A>G) is associated with 3-methylcrotonyl-CoA carboxylase 2 deficiency (ClinVar).

How common is MCCC2 p.Arg327Gly (c.979A>G) in the general population?

MCCC2 p.Arg327Gly (c.979A>G) is very rare (popmax 0.000254%, nfe) (gnomAD).

How is 3-methylcrotonyl-CoA carboxylase deficiency inherited?

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

What do computational predictors say about MCCC2 p.Arg327Gly (c.979A>G)?

AlphaMissense predicts likely benign (score 0.2026) — an in-silico prediction, not a clinical call.

MCCC2 p.Arg327Gly

c.979A>G · VCV4057535

Uncertain significance No assertion criteria

Classification

Uncertain significance

ClinVar

Review

No assertion criteria ☆☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.2026 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.000254%, nfe)

Missense predictors

2/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

3-methylcrotonyl-CoA carboxylase 2 deficiency

Computational evidence

Protein change
AlphaMissense	0.2026	likely benign
REVEL	0.891	moderately pathogenic-leaning
SaProt	LLR -14.38	damaging
⇒ REVEL and SaProt call this damaging; AlphaMissense does not.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 5.2	GERP 0.57, phastCons 1
Regional constraint	o/e 0.97	unconstrained · MANE · 69 kb · p 0.42 · regional, not allelic
Overall
CADD	24.8	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 0.000254% European (non-Finnish) · 3/1,179,980 alleles

Filtering AF 6.8e-05% ClinGen BA1/BS1 input FAF95, joint · FAF99 1.9e-05%

Overall 0.000342% 5/1,461,806 alleles · very rare

Ancestry group	Frequency	1 in
Finnishnot grpmax-eligible	0.00312%	32,018
European (non-Finnish)grpmax	0.000254%	393,326

Finnish 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: MCCC2
Protein: p.Arg327Gly
Coding: c.979A>G
MANE Select: NM_022132
Type: single nucleotide variant
Location: chr5:71635226 (GRCh38)
Gene constraint: LOEUF 0.832 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 94.82 · 14 PDB
Residue 327: a β-strand; the coa carboxyltransferase c-terminal domain; the 'carboxyltransferase' region

Full MCCC2 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

3-methylcrotonyl-CoA carboxylase 2 deficiency — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For 3-methylcrotonyl-CoA carboxylase deficiency (Orphanet):

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

Similar variants

MCCC2 p.Arg327= Uncertain significance same residue
MCCC2 p.Arg327Lys Uncertain significance ⚠ same residue
MCCC2 c.1000-2A>G Likely pathogenic ★★ same condition
MCCC2 c.1072+1G>A Likely pathogenic ★★ same condition
MCCC2 c.1149+1G>A Pathogenic/Likely pathogenic ★★ same condition
MCCC2 c.1149+1G>T Pathogenic/Likely pathogenic ★★ same condition
MCCC2 c.1216+1G>A Likely pathogenic ★★ same condition
MCCC2 c.1216+2T>A Pathogenic/Likely 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/mccc2-p-arg327gly (accessed [today's date]).

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