TBC1D3B

Chr 17

TBC1 domain family member 3B

Also known as: PRC17, TBC1D3I

NCBI Gene: 414059 ENSG00000274808 UniProt: A6NDS4

This gene encodes a protein that is similar to TBC1 domain family, member 3. This protein contains a TBC (Tre-2, Bub2p, and Cdc16p) domain, which is found in proteins involved in RAB GTPase signaling and vesicle trafficking. There are multiple copies of this gene located within a cluster of chemokine genes on chromosome 17q. [provided by RefSeq, Apr 2009]

Active trials

Pathogenic / LP

ClinVar variants

Pubs (1 yr)

-0.0

Missense Z

1.46

LOEUF

Clinical Summary— TBC1D3B

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Population Constraint (gnomAD)

Constrained for loss-of-function variants (OE-LoF 0.33) despite low pLI — interpret in context.

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ClinVar Variants

32 Pathogenic / Likely Pathogenic· 5 VUS of 48 total submissions

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.

1.46LOEUF

pLI 0.219

Z-score 1.08

OE 0.33 (0.12–1.46)

Tolerant

Highly tolerant — LoF variants common in population

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.

-0.03Z-score

OE missense 1.01 (0.79–1.31)

42 obs / 41.4 exp

Tolerant

Tolerant to missense variation

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.0.33 (0.12–1.46)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.1.01 (0.79–1.31)

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.0.70

0≤1.21.6

LoF obs/exp: 1 / 3.0Missense obs/exp: 42 / 41.4Syn Z: 1.00

0.75top 25%

GOF

0.79top 25%

LOF

0.2582th %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.