Functional Evaluation of AMD-Associated Risk Variants of Complement Factor B

Area of Science:

• Genetics and Molecular Biology
• Ophthalmology
• Immunology

Background:

• Neovascular age-related macular degeneration (AMD) pathogenesis involves angiogenesis.
• Complement factor B (CFB) gene variants, specifically 32W and 32Q, are linked to reduced neovascular AMD risk compared to the common 32R allele.

Purpose of the Study:

• To investigate whether the protective CFB R32Q variant influences the neovascularization process in a manner consistent with its reduced association with AMD.
• To functionally characterize the biological activities of CFB variants R32R, R32W, and R32Q in angiogenesis.

Main Methods:

• Expression and purification of human CFB variants (32R, 32W, 32Q).
• Utilized an ex vivo mouse fetal metatarsal explant model to assess angiogenesis.
• Quantified angiogenesis via immunostaining; measured C3 and VEGF protein levels using ELISAs; assessed gene expression (Cfb, C3, Vegf) via quantitative PCR.

Main Results:

• The three CFB variants exhibited distinct biological activities in the mouse metatarsal assay.
• CFBR32 demonstrated significantly greater angiogenic activity than CFBQ32 and CFBW32, which showed similar activities.
• Observed differences in macrophage phenotypes associated with CFBQ32 and CFBW32 may influence their angiogenic effects.

Conclusions:

• The observed biological activities of CFB variants R32R, R32W, and R32Q correlate with their known associations with AMD risk.
• Provided functional evidence supporting the role of these CFB variants in angiogenesis, potentially relevant to neovascular AMD pathogenesis.