Rare genetic variants in the CFI gene are associated with advanced age-related macular degeneration and commonly result in reduced serum factor I levels

Hum Mol Genet. 2015 Jul 1;24(13):3861-70. doi: 10.1093/hmg/ddv091. Epub 2015 Mar 18.


To assess a potential diagnostic and therapeutic biomarker for age-related macular degeneration (AMD), we sequenced the complement factor I gene (CFI) in 2266 individuals with AMD and 1400 without, identifying 231 individuals with rare genetic variants. We evaluated the functional impact by measuring circulating serum factor I (FI) protein levels in individuals with and without rare CFI variants. The burden of very rare (frequency <1/1000) variants in CFI was strongly associated with disease (P = 1.1 × 10(-8)). In addition, we examined eight coding variants with counts ≥5 and saw evidence for association with AMD in three variants. Individuals with advanced AMD carrying a rare CFI variant had lower mean FI compared with non-AMD subjects carrying a variant (P < 0.001). Further new evidence that FI levels drive AMD risk comes from analyses showing individuals with a CFI rare variant and low FI were more likely to have advanced AMD (P = 5.6 × 10(-5)). Controlling for covariates, low FI increased the risk of advanced AMD among those with a variant compared with individuals without advanced AMD with a rare CFI variant (OR 13.6, P = 1.6 × 10(-4)), and also compared with control individuals without a rare CFI variant (OR 19.0, P = 1.1 × 10(-5)). Thus, low FI levels are strongly associated with rare CFI variants and AMD. Enhancing FI activity may be therapeutic and measuring FI provides a screening tool for identifying patients who are most likely to benefit from complement inhibitory therapy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Complement Factor I / genetics*
  • Complement Factor I / metabolism
  • Female
  • Fibrinogen / metabolism*
  • Genetic Variation
  • Humans
  • Macular Degeneration / genetics*
  • Macular Degeneration / metabolism
  • Macular Degeneration / pathology
  • Male


  • Fibrinogen
  • CFI protein, human
  • Complement Factor I