F12

Chr 5ADAR

coagulation factor XII

Also known as: HAE3, HAEX, HAF

NCBI Gene: 2161 ENSG00000131187 UniProt: P00748

This gene encodes coagulation factor XII which circulates in blood as a zymogen. This single chain zymogen is converted to a two-chain serine protease with an heavy chain (alpha-factor XIIa) and a light chain. The heavy chain contains two fibronectin-type domains, two epidermal growth factor (EGF)-like domains, a kringle domain and a proline-rich domain, whereas the light chain contains only a catalytic domain. On activation, further cleavages takes place in the heavy chain, resulting in the production of beta-factor XIIa light chain and the alpha-factor XIIa light chain becomes beta-factor XIIa heavy chain. Prekallikrein is cleaved by factor XII to form kallikrein, which then cleaves factor XII first to alpha-factor XIIa and then to beta-factor XIIa. The active factor XIIa participates in the initiation of blood coagulation, fibrinolysis, and the generation of bradykinin and angiotensin. It activates coagulation factors VII and XI. Defects in this gene do not cause any clinical symptoms and the sole effect is that whole-blood clotting time is prolonged. [provided by RefSeq, Jul 2008]

Primary Disease Associations & Inheritance

Angioedema, hereditary, 3MIM #610618

Factor XII deficiencyMIM #234000

Active trials

Pathogenic / LP

302

ClinVar variants

Pubs (1 yr)

0.9

Missense Z

0.78

LOEUF

Clinical Summary— F12

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Gene-Disease Validity (ClinGen)

congenital factor XII deficiency · ARDefinitive

Definitive — sufficient evidence for diagnostic panels

2 total gene-disease associations curated

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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

74 Pathogenic / Likely Pathogenic· 127 VUS of 302 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.

0.78LOEUF

pLI 0.000

Z-score 2.57

OE 0.52 (0.35–0.78)

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.

0.92Z-score

OE missense 0.86 (0.79–0.95)

307 obs / 356.1 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.0.52 (0.35–0.78)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.86 (0.79–0.95)

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.0.95

0≤1.21.6

LoF obs/exp: 17 / 32.9Missense obs/exp: 307 / 356.1Syn Z: 0.48

0.6452th %ile

GOF

0.6737th %ile

LOF

0.2874th %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 · 1 literature citation

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.

Literature Evidence

GOFThe data strongly suggested that T328K is a gain-of-function mutation that markedly increases F12 amadolytic activity but that does not alter F12 plasma levels.PMID:17186468

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