FCN2

Chr 9

ficolin 2

Also known as: EBP-37, FCNL, P35, ficolin-2

NCBI Gene: 2220 ENSG00000160339 UniProt: Q15485

The product of this gene belongs to the ficolin family of proteins. This family is characterized by the presence of a leader peptide, a short N-terminal segment, followed by a collagen-like region, and a C-terminal fibrinogen-like domain. This gene is predominantly expressed in the liver, and has been shown to have carbohydrate binding and opsonic activities. Alternatively spliced transcript variants encoding different isoforms have been identified. [provided by RefSeq, Jul 2008]

Active trials

Pathogenic / LP

119

ClinVar variants

Pubs (1 yr)

-0.4

Missense Z

1.53

LOEUF

Clinical Summary— FCN2

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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

45 Pathogenic / Likely Pathogenic· 65 VUS of 119 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.

1.53LOEUF

pLI 0.000

Z-score -0.03

OE 1.01 (0.68–1.53)

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.

-0.36Z-score

OE missense 1.07 (0.96–1.21)

204 obs / 190.0 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.1.01 (0.68–1.53)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.1.07 (0.96–1.21)

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.1.11

0≤1.21.6

LoF obs/exp: 16 / 15.9Missense obs/exp: 204 / 190.0Syn Z: -0.77

0.7229th %ile

GOF

0.6541th %ile

LOF

0.2970th %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.