Is MTHFR p.Ala155= (c.465G>T) pathogenic?

MTHFR p.Ala155= (c.465G>T) is classified Likely benign in MTHFR (ClinVar, Multiple submitters, 4 submitters; last evaluated 2024-12-05). Rare (popmax 0.215%, sas); Associated with homocystinuria due to methylene tetrahydrofolate reductase deficiency.

What condition is associated with MTHFR p.Ala155= (c.465G>T)?

MTHFR p.Ala155= (c.465G>T) is associated with homocystinuria due to methylene tetrahydrofolate reductase deficiency (ClinVar).

How common is MTHFR p.Ala155= (c.465G>T) in the general population?

MTHFR p.Ala155= (c.465G>T) is rare (popmax 0.215%, sas) (gnomAD).

MTHFR p.Ala155=

Q: How is Homocystinuria due to methylene tetrahydrofolate reductase deficiency inherited?

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

c.465G>T · rs566125423 · VCV699346

Likely benign Multiple submitters

Classification

Likely benign

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 4 submitters

gnomAD v4.1

Rare

rare (popmax 0.215%, sas)

Conditions

homocystinuria due to methylene tetrahydrofolate reductase deficiency

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP -16	GERP -3.1
Overall
CADD	0.063	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.215% South Asian · 196/91,052 alleles

Filtering AF 0.191% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.181%

Overall 0.0128% 206/1,613,338 alleles · rare

Ancestry group	Frequency	1 in
South Asiangrpmax	0.215%	465
Remaining individualsnot grpmax-eligible	0.0144%	6,936
European (non-Finnish)	8.47e-05%	1,180,022

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: MTHFR
Protein: p.Ala155=
Coding: c.465G>T
MANE Select: NM_005957
dbSNP: rs566125423
Type: single nucleotide variant
Location: chr1:11801171 (GRCh38)
Gene constraint: LOEUF 0.859 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 89.13 · 4 PDB
Residue 155: a β-strand

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

Disease context

homocystinuria due to methylene tetrahydrofolate reductase deficiency — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Homocystinuria due to methylene tetrahydrofolate reductase deficiency (Orphanet):

Inheritance: Autosomal recessive
Onset: Infancy, Neonatal

Similar variants

MTHFR c.1166+1G>T Likely pathogenic ★★ same condition
MTHFR c.1166+5G>C Pathogenic/Likely pathogenic ★★ same condition
MTHFR c.1347+1G>A Pathogenic ★★ same condition
MTHFR c.1348-1G>C Likely pathogenic ★★ same condition
MTHFR c.1530+1G>A Likely pathogenic ★★ same condition
MTHFR c.1530+1G>T Likely pathogenic ★★ same condition
MTHFR c.1632+2T>G Pathogenic/Likely pathogenic ★★ same condition
MTHFR c.1752+1G>T 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/mthfr-p-ala155 (accessed [today's date]).

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