Is TTC8 p.Trp226Arg (c.676T>C) pathogenic?

TTC8 p.Trp226Arg (c.676T>C) is classified Uncertain significance in TTC8 (ClinVar, Single submitter, 1 submitter; last evaluated 2024-11-11). Absent from gnomAD v4.1; Associated with Bardet-Biedl syndrome.

What condition is associated with TTC8 p.Trp226Arg (c.676T>C)?

TTC8 p.Trp226Arg (c.676T>C) is associated with Bardet-Biedl syndrome (ClinVar).

How common is TTC8 p.Trp226Arg (c.676T>C) in the general population?

TTC8 p.Trp226Arg (c.676T>C) is absent from gnomAD v4.1 (gnomAD).

How is Bardet-Biedl syndrome inherited?

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

TTC8 p.Trp226Arg

c.676T>C · rs2140999509 · VCV1485560

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Absent

absent from gnomAD v4.1

Conditions

Bardet-Biedl syndrome

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
REVEL	0.57	indeterminate
Splicing
SpliceAI	<0.2	all four deltas below 0.2 · T>G here scores Δ0.25 · evaluated, not missing
Constraint at this position
Conservation	phyloP 7.9	GERP 1.7, phastCons 1
Regional constraint	o/e 0.98	unconstrained · MANE · 53 kb · p 0.62 · regional, not allelic
Overall
CADD	27.9	PHRED · no single calibrated threshold — expert panels disagree

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: TTC8
Protein: p.Trp226Arg
Coding: c.676T>C
MANE Select: NM_144596
dbSNP: rs2140999509
Type: single nucleotide variant
Location: chr14:88853022 (GRCh38)
Gene constraint: LOEUF 0.8 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 84.48

Full TTC8 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

Bardet-Biedl syndrome — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Bardet-Biedl syndrome (Orphanet):

Inheritance: Autosomal recessive, Oligogenic
Onset: Antenatal, Childhood, Infancy, Neonatal
Prevalence: 1-9 / 100 000 (Specific population)

Similar variants

TTC8 p.Trp226Ter Pathogenic/Likely pathogenic ★★ same residue
TTC8 c.114+2T>C Pathogenic/Likely pathogenic ★★ same condition
TTC8 c.265+1G>A Pathogenic/Likely pathogenic ★★ same condition
TTC8 c.799-2A>G Likely pathogenic ★★ same condition
TTC8 p.Gln187Ter Pathogenic/Likely pathogenic ★★ same condition
TTC8 p.Gln247Ter Pathogenic/Likely pathogenic ★★ same condition
TTC8 p.Gln86Ter Pathogenic ★★ same condition
TTC8 p.Thr163= 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/ttc8-p-trp226arg (accessed [today's date]).

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