FBP1

Chr 9AR

fructose-bisphosphatase 1

Also known as: FBP

NCBI Gene: 2203 ENSG00000165140 UniProt: P09467

Fructose-1,6-bisphosphatase 1, a gluconeogenesis regulatory enzyme, catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate. Fructose-1,6-diphosphatase deficiency is associated with hypoglycemia and metabolic acidosis. [provided by RefSeq, Jul 2008]

Primary Disease Associations & Inheritance

Fructose-1,6-bisphosphatase deficiencyMIM #229700

Active trials

Pathogenic / LP

389

ClinVar variants

Pubs (1 yr)

0.7

Missense Z

0.72

LOEUF

Clinical Summary— FBP1

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Gene-Disease Validity (ClinGen)

fructose-1,6-bisphosphatase deficiency · ARDefinitive

Definitive — sufficient evidence for diagnostic panels

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Population Constraint (gnomAD)

Constrained for loss-of-function variants (OE-LoF 0.32) despite low pLI — interpret in context.

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ClinVar Variants

96 Pathogenic / Likely Pathogenic· 80 VUS of 389 total submissions

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GeneReview available — FBP1

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.

0.72LOEUF

pLI 0.079

Z-score 2.25

OE 0.32 (0.15–0.72)

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.

0.74Z-score

OE missense 0.85 (0.75–0.97)

170 obs / 199.4 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.0.32 (0.15–0.72)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.85 (0.75–0.97)

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.1.20

0≤1.21.6

LoF obs/exp: 4 / 12.7Missense obs/exp: 170 / 199.4Syn Z: -1.45

0.76top 25%

GOF

0.72top 25%

LOF

0.2679th %ile

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

DNprediction above median

GOFprediction 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.