Is MTR p.Ile435= (c.1305T>C) pathogenic?

MTR p.Ile435= (c.1305T>C) is classified Benign in MTR (ClinVar, Single submitter, 1 submitter; last evaluated 2023-11-15). Very rare (popmax 0.00017%, nfe); Associated with methylcobalamin deficiency type cblG.

What condition is associated with MTR p.Ile435= (c.1305T>C)?

MTR p.Ile435= (c.1305T>C) is associated with methylcobalamin deficiency type cblG (ClinVar).

How common is MTR p.Ile435= (c.1305T>C) in the general population?

MTR p.Ile435= (c.1305T>C) is very rare (popmax 0.00017%, nfe) (gnomAD).

How is Homocystinuria without methylmalonic aciduria inherited?

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

MTR p.Ile435=

c.1305T>C · rs775502272 · VCV2886583

Benign Single submitter

Classification

Benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00017%, nfe)

Conditions

methylcobalamin deficiency type cblG

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 -0.66	GERP -5.6, phastCons 0.047
Overall
CADD	6.148	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00017% European (non-Finnish) · 2/1,179,720 alleles

Filtering AF 2.8e-05% ClinGen BA1/BS1 input FAF95, joint · FAF99 1.1e-05%

Overall 0.00378% 61/1,612,264 alleles · very rare

Ancestry group	Frequency	1 in
Finnishnot grpmax-eligible	0.0893%	1,120
Remaining individualsnot grpmax-eligible	0.0032%	31,218
European (non-Finnish)grpmax	0.00017%	589,859

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: MTR
Protein: p.Ile435=
Coding: c.1305T>C
MANE Select: NM_000254
dbSNP: rs775502272
Type: single nucleotide variant
Location: chr1:236835663 (GRCh38)
Gene constraint: LOEUF 0.625 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 87.60 · 9 PDB
Residue 435: the pterin-binding domain; an α-helix

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

Disease context

methylcobalamin deficiency type cblG — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Homocystinuria without methylmalonic aciduria (Orphanet):

Inheritance: Autosomal recessive
Onset: All ages

Similar variants

MTR c.1812+1G>A Likely pathogenic ★★ same condition
MTR c.2474-1G>C Pathogenic ★★ same condition
MTR c.2595-2A>G Likely pathogenic ★★ same condition
MTR c.340-166A>G Pathogenic/Likely pathogenic ★★ same condition
MTR c.609+1088G>A Pathogenic ★★ same condition
MTR c.866-2A>C Pathogenic/Likely pathogenic ★★ same condition
MTR p.Arg1147Ter Pathogenic ★★ same condition
MTR p.Arg585Ter 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/mtr-p-ile435 (accessed [today's date]).

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