Is MTHFR p.Ala175Ser (c.523G>T) pathogenic?

MTHFR p.Ala175Ser (c.523G>T) is classified Uncertain significance in MTHFR (ClinVar, No assertion criteria, 1 submitter; last evaluated 2025-01-11). AlphaMissense: likely benign (0.1991); Absent from gnomAD v4.1; Associated with homocystinuria due to methylene tetrahydrofolate reductase deficiency.

What condition is associated with MTHFR p.Ala175Ser (c.523G>T)?

MTHFR p.Ala175Ser (c.523G>T) is associated with homocystinuria due to methylene tetrahydrofolate reductase deficiency (ClinVar).

How common is MTHFR p.Ala175Ser (c.523G>T) in the general population?

MTHFR p.Ala175Ser (c.523G>T) is absent from gnomAD v4.1 (gnomAD).

What do computational predictors say about MTHFR p.Ala175Ser (c.523G>T)?

AlphaMissense predicts likely benign (score 0.1991) — an in-silico prediction, not a clinical call.

MTHFR p.Ala175Ser

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.523G>T · VCV4057955

Uncertain significance No assertion criteria

Classification

Uncertain significance

ClinVar

Review

No assertion criteria ☆☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.1991 · ACMG-weighted

gnomAD v4.1

Absent

absent from gnomAD v4.1

Missense predictors

1/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

homocystinuria due to methylene tetrahydrofolate reductase deficiency

Computational evidence

Protein change
AlphaMissense	0.1991	likely benign
REVEL	0.776	moderately pathogenic-leaning
SaProt	LLR -9.97	tolerated
⇒ REVEL calls this damaging; AlphaMissense and SaProt do not.
Splicing
SpliceAI	<0.2	no splice effect predicted · four deltas, not one · how we know
Constraint at this position
Conservation	phyloP 7.6	GERP 1.7, phastCons 1
Regional constraint	o/e 0.85	unconstrained · MANE · 12 kb · p 1.7e-05 · regional, not allelic
Overall
CADD	25.4	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

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: MTHFR
Protein: p.Ala175Ser
Coding: c.523G>T
MANE Select: NM_005957
Type: single nucleotide variant
Location: chr1:11800275 (GRCh38)
Gene constraint: LOEUF 0.859 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 89.13 · 4 PDB
Residue 175: a binding site; an α-helix; a UniProt-annotated variant site (in mthfrd; reduced methylenetetrahydrofolate reductase activity; reduced affinity for nadph)

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 p.Ala175Thr Pathogenic/Likely pathogenic ★★ same residue
MTHFR p.Ala175Glu Uncertain significance ★ ⚠ same residue
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

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-ala175ser (accessed [today's date]).

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