FCN3 Gene

CN3 (CN3 stands for "ficolin 3") is a protein coding gene located at chromosome 1p36.11. The encoded proteins, the ficolins are a group of proteins consisting of a collagen-like domain and a fibrinogen-like domain.

Two types of ficolins exist in human serum, both of which have lectin activity. The protein encoded by this gene is a thermolabile beta-2 macroglycoprotein that is found throughout human serum and belongs to the ficolin/opsonin p35 lectin family.

The protein, originally identified based on its reactivity with sera from patients with systemic lupus erythematosus, has been shown to have calcium-independent lectin activity. The protein, in conjunction with MASPs and sMAP, can activate the complement pathway and thus contribute to host defense by activating the lectin pathway. Alternative splicing occurs at this locus, and two variants have been identified, each encoding a specific isoform.

Diseases associated with FCN3 include ficolin 3 deficiency (Immunodeficiency due to ficolin 3 deficiency; OMIM: 613860).

Related signaling pathways include the immune response, lectin-induced complement pathway, and innate immune system. Ficolin3 may have a function in innate immunity through activation of the lectin complement pathway.

1. Michalski M et al. (2015) Primary ficolin-3 deficiency--is it associated with increased susceptibility to infections? (Letter) Immunobiology 220: 711-713.
2. Michalski M et al. (2012) H-ficolin (ficolin-3) concentrations and FCN3 gene polymorphism in neonates. Immunobiology 217: 730-737.
3. Munthe-Fog L et al (2009) Immunodeficiency associated with FCN3 mutation and ficolin-3 deficiency. New Eng J Med 360: 2637-2644.
4. Schlapbach LJ et al (2011) Congenital H-ficolin deficiency in premature infants with severe necrotising enterocolitis. (Letter) Gut 60: 1438-1439.