Is MECP2 p.Ser77= (c.231A>G) pathogenic?

MECP2 p.Ser77= (c.231A>G) is classified Likely benign in MECP2 (ClinVar, Single submitter, 1 submitter; last evaluated 2023-11-28). Ultra-rare (popmax 0.0236%, eas); Associated with severe neonatal-onset encephalopathy with microcephaly.

What condition is associated with MECP2 p.Ser77= (c.231A>G)?

MECP2 p.Ser77= (c.231A>G) is associated with severe neonatal-onset encephalopathy with microcephaly (ClinVar).

How common is MECP2 p.Ser77= (c.231A>G) in the general population?

MECP2 p.Ser77= (c.231A>G) is ultra-rare (popmax 0.0236%, eas) (gnomAD).

How is MECP2-related severe neonatal encephalopathy inherited?

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

MECP2 p.Ser77=

c.231A>G · rs781905548 · VCV2971737

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

ultra-rare (popmax 0.0236%, eas)

Conditions

severe neonatal-onset encephalopathy with microcephaly

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 -2.6	GERP -3.7
Overall
CADD	0.801	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0236% East Asian · 8/33,860 alleles

Filtering AF 0.0117% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00849%

Overall 0.000742% 9/1,212,610 alleles · ultra-rare exomes 9/1,098,207 · genomes 0/114,403 · joint denominator

Ancestry group	Frequency	1 in
East Asiangrpmax	0.0236%	4,232
Remaining individualsnot grpmax-eligible	0.0021%	47,658

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: MECP2
Protein: p.Ser77=
Coding: c.231A>G
MANE Select: NM_001110792
dbSNP: rs781905548
Type: single nucleotide variant
Location: chrX:154032389 (GRCh38)
Structure: AlphaFold pLDDT 57.25 · 11 PDB
Residue 77: the 'disordered' region

Full MECP2 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

severe neonatal-onset encephalopathy with microcephaly — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For MECP2-related severe neonatal encephalopathy (Orphanet):

Inheritance: X-linked recessive
Onset: Infancy, Neonatal

Similar variants

MECP2 p.Ser77Ter Pathogenic/Likely pathogenic ★★ same residue
MECP2 p.Ser77Leu Pathogenic ★ ⚠ same residue
MECP2 c.414-3C>G Pathogenic ★★★ same condition
MECP2 c.62+1G>A Pathogenic ★★★ same condition
MECP2 p.Ala291Val Likely pathogenic ★★★ ⚠ same condition
MECP2 p.Arg127His Pathogenic ★★★ same condition
MECP2 p.Arg145Cys Pathogenic ★★★ same condition
MECP2 p.Arg145His 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/mecp2-p-ser77 (accessed [today's date]).

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