Is BBS2 p.Arg643Cys (c.1927C>T) pathogenic?

BBS2 p.Arg643Cys (c.1927C>T) is classified Uncertain significance in BBS2 (ClinVar, Multiple submitters, 6 submitters; last evaluated 2024-04-16). AlphaMissense: likely benign (0.1507); Ultra-rare (popmax 0.0588%, afr); Associated with Bardet-Biedl syndrome.

What condition is associated with BBS2 p.Arg643Cys (c.1927C>T)?

BBS2 p.Arg643Cys (c.1927C>T) is associated with Bardet-Biedl syndrome, Bardet-Biedl syndrome 2, retinitis pigmentosa 74 (ClinVar).

How common is BBS2 p.Arg643Cys (c.1927C>T) in the general population?

BBS2 p.Arg643Cys (c.1927C>T) is ultra-rare (popmax 0.0588%, afr) (gnomAD).

How is Bardet-Biedl syndrome inherited?

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

What do computational predictors say about BBS2 p.Arg643Cys (c.1927C>T)?

AlphaMissense predicts likely benign (score 0.1507) — an in-silico prediction, not a clinical call.

BBS2 p.Arg643Cys

c.1927C>T · rs147397090 · VCV858439

Uncertain significance Multiple submitters

Classification

Uncertain significance

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 6 submitters

AlphaMissense

likely benign

0.1507 · ACMG-weighted

gnomAD v4.1

Rare

ultra-rare (popmax 0.0588%, afr)

Missense predictors

1/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

Bardet-Biedl syndrome

Computational evidence

Protein change
AlphaMissense	0.1507	likely benign
REVEL	0.7	pathogenic-leaning
SaProt	LLR -6.35	tolerated
⇒ REVEL calls this damaging; AlphaMissense and SaProt do not.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 6.5	GERP 1.8, phastCons 1
Regional constraint	o/e 0.87	unconstrained · MANE · 35 kb · p 9.6e-05 · regional, not allelic
Overall
CADD	23.8	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

Grpmax group 0.0588% African / African-American · 44/74,872 alleles

Filtering AF 0.0449% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.0401%

Overall 0.00366% 59/1,613,484 alleles · ultra-rare

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.0588%	1,702
Admixed American	0.005%	19,989
Remaining individualsnot grpmax-eligible	0.0032%	31,238
Finnishnot grpmax-eligible	0.00156%	63,954
South Asian	0.0011%	91,022
European (non-Finnish)	0.000678%	147,465

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: BBS2
Protein: p.Arg643Cys
Coding: c.1927C>T
MANE Select: NM_031885
dbSNP: rs147397090
Type: single nucleotide variant
Location: chr16:56485722 (GRCh38)
Gene constraint: LOEUF 0.892 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 89.49
Residue 643: a UniProt-annotated variant site (in bbs2)

Full BBS2 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

Also linked: Bardet-Biedl syndrome 2 retinitis pigmentosa 74

For Bardet-Biedl syndrome (Orphanet):

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

Similar variants

BBS2 p.Arg643His Uncertain significance ★★ ⚠ same residue
BBS2 c.118-1G>T Likely pathogenic ★★ same condition
BBS2 c.118-2A>C Likely pathogenic ★★ same condition
BBS2 c.118-2A>G Likely pathogenic ★★ same condition
BBS2 c.1225+2T>C Likely pathogenic ★★ same condition
BBS2 c.1225+2T>G Likely pathogenic ★★ same condition
BBS2 c.1397+1G>A Pathogenic/Likely pathogenic ★★ same condition
BBS2 c.1397+2T>C 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/bbs2-p-arg643cys (accessed [today's date]).

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