CRB2

Chr 9AR

crumbs cell polarity complex component 2

Also known as: FSGS9, VMCKD

NCBI Gene: 286204 ENSG00000148204 UniProt: Q5IJ48

This gene encodes a member of a family of proteins that are components of the Crumbs cell polarity complex. In mammals, members of this family are thought to play a role in many cellular processes in early embryonic development. A similar protein in Drosophila determines apicobasal polarity in embryonic epithelial cells. Mutations in this gene are associated with focal segmental glomerulosclerosis 9, and with ventriculomegaly with cystic kidney disease. [provided by RefSeq, Aug 2016]

Primary Disease Associations & Inheritance

Focal segmental glomerulosclerosis 9MIM #616220

Ventriculomegaly with cystic kidney diseaseMIM #219730

UniProtRetinitis pigmentosa

Active trials

Pathogenic / LP

494

ClinVar variants

Pubs (1 yr)

1.1

Missense Z

0.89

LOEUF

Clinical Summary— CRB2

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Gene-Disease Validity (ClinGen)

focal segmental glomerulosclerosis 9 · ARDefinitive

Definitive — sufficient evidence for diagnostic panels

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Population Constraint (gnomAD)

Low constraint (pLI 0.00) — loss-of-function variants are relatively tolerated in the population.

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ClinVar Variants

52 Pathogenic / Likely Pathogenic· 176 VUS of 494 total submissions

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GeneReview available — CRB2

Authoritative clinical overview · Recommended first read

Open GeneReview ↗

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

Tolerant — LoF & missense variants common in population

LoF Constraint?LOEUF (Loss-of-function Observed/Expected Upper bound Fraction) is the upper bound of the 90% CI for LoF OE — the preferred gnomAD v4 metric. Lower = more intolerant to LoF. LOEUF < 0.35 = highly constrained.

0.89LOEUF

pLI 0.000

Z-score 2.16

OE 0.65 (0.48–0.89)

Tolerant

Typical tolerance to LoF variation

Missense Constraint?Missense Z-score: standard deviations fewer missense variants observed vs. expected. Z > 3.09 (p < 0.001) = gene does not tolerate missense variation. OE missense < 0.6 is also considered constrained.

1.11Z-score

OE missense 0.89 (0.83–0.94)

662 obs / 747.1 exp

Tolerant

Mild missense constraint

Observed / Expected Ratios?Shaded band = 90% confidence interval. Vertical tick = point estimate. Grey threshold line = gnomAD constraint cutoff for that variant class.

LoF OE?Ratio of observed to expected LoF variants. Upper CI bound (LOEUF) ≤ 0.35 = strong LoF constraint signal.0.65 (0.48–0.89)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.89 (0.83–0.94)

0≤0.61.4

Synonymous OE?Control metric — synonymous variants are largely neutral and expected near OE = 1.0. Significant deviation may indicate annotation issues.1.02

0≤1.21.6

LoF obs/exp: 29 / 44.5Missense obs/exp: 662 / 747.1Syn Z: -0.25

0.6162th %ile

GOF

0.7126th %ile

LOF

0.3066th %ile

This gene has evidence for multiple mechanisms of pathogenicity (gain-of-function and dominant-negative). Both the Badonyi & Marsh prediction and the broader genomic evidence point to gain-of-function as the predominant mechanism. Different variants in this gene may act through different mechanisms — interpret in context of the specific variant.

GOFprediction above median

DNprediction above median

Note: In-silico variant effect predictors (SIFT, PolyPhen, REVEL, CADD) may underestimate pathogenicity of missense variants in genes with GOF or DN mechanisms. Consider functional evidence and clinical context.

Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312.