Is SYNJ1 p.Pro1256Ser (c.3766C>T) pathogenic?

SYNJ1 p.Pro1256Ser (c.3766C>T) is classified Uncertain significance in SYNJ1 (ClinVar, Single submitter, 1 submitter; last evaluated 2022-06-27). Very rare (popmax 0.00267%, afr); Associated with developmental and epileptic encephalopathy, 53.

What condition is associated with SYNJ1 p.Pro1256Ser (c.3766C>T)?

SYNJ1 p.Pro1256Ser (c.3766C>T) is associated with developmental and epileptic encephalopathy, 53, early-onset Parkinson disease 20 (ClinVar).

How common is SYNJ1 p.Pro1256Ser (c.3766C>T) in the general population?

SYNJ1 p.Pro1256Ser (c.3766C>T) is very rare (popmax 0.00267%, afr) (gnomAD).

SYNJ1 p.Pro1256Ser

c.3766C>T · rs138334718 · VCV1425394

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00267%, afr)

Conditions

developmental and epileptic encephalopathy, 53

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
REVEL	0.166	moderately benign-leaning
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 1.2	GERP 0.98, phastCons 0.74
Regional constraint	o/e 0.99	unconstrained · MANE · 12 kb · p 0.77 · regional, not allelic
Overall
CADD	17.58	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00267% African / African-American · 2/75,024 alleles

Filtering AF 0.000442% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000166%

Overall 0.000186% 3/1,614,100 alleles · very rare

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.00267%	37,512
South Asian	0.0011%	91,076

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: SYNJ1
Protein: p.Pro1256Ser
Coding: c.3766C>T
MANE Select: NM_203446
dbSNP: rs138334718
Type: single nucleotide variant
Location: chr21:32639057 (GRCh38)
Gene constraint: LOEUF 0.539 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 68.09 · 5 PDB
Residue 1256: the 'disordered' region

Full SYNJ1 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

developmental and epileptic encephalopathy, 53 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: early-onset Parkinson disease 20

Similar variants

SYNJ1 p.Pro1256Leu Uncertain significance ★★ same residue
SYNJ1 c.1201-2A>G Likely pathogenic ★★ same condition
SYNJ1 c.2461+2T>C Likely pathogenic ★★ same condition
SYNJ1 c.3478+1G>A Likely pathogenic ★★ same condition
SYNJ1 p.Arg219Gln Pathogenic ★★ same condition
SYNJ1 p.Arg534Ter Pathogenic/Likely pathogenic ★★ same condition
SYNJ1 p.Arg709Ter Pathogenic/Likely pathogenic ★★ same condition
SYNJ1 p.Gln748Ter 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/synj1-p-pro1256ser (accessed [today's date]).

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