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    Topic review

    CFI Gene

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    Submitted by: Vicky Zhou
    (This entry belongs to Entry Collection "MedlinePlus ")

    Definition

    complement factor I

    1. Normal Function

    The CFI gene provides instructions for making a protein called complement factor I. This protein helps regulate a part of the body's immune response known as the complement system. The complement system is a group of proteins that work together to destroy foreign invaders (such as bacteria and viruses), trigger inflammation, and remove debris from cells and tissues. This system must be carefully regulated so it targets only unwanted materials and does not attack the body's healthy cells. Complement factor I and several related proteins protect healthy cells by preventing activation of the complement system when it is not needed.

    2. Health Conditions Related to Genetic Changes

    2.1. Complement factor I deficiency

    At least 10 mutations in the CFI gene have been identified in people with complement factor I deficiency, a disorder characterized by immune system dysfunction. The mutations result in abnormal, nonfunctional, or absent complement factor I.

    The lack (deficiency) of functional complement factor I protein allows uncontrolled activation of the complement system. The unregulated activity of the complement system decreases blood levels of another complement protein called C3, reducing the immune system's ability to fight infections. In addition, the immune system may malfunction and attack its own tissues, resulting in autoimmune disorders.

    2.2. Age-Related Macular Degeneration

    Age-related macular degeneration

    2.3. Atypical Hemolytic-Uremic Syndrome

    Atypical hemolytic-uremic syndrome

    2.4. C3 Glomerulopathy

    C3 glomerulopathy

    2.5. Other Disorders

    Mutations in the CFI gene have also been found in people with glomerulonephritis with isolated C3 deposits. This condition, which may also occur in people with complement factor I deficiency, is characterized by kidney malfunction that can be serious or life-threatening. The CFI gene mutations identified in this disorder result in an abnormal or nonfunctional version of complement factor I. The defective protein allows uncontrolled activation of the complement system. The overactive complement system attacks certain kidney cells, which damages the kidneys and leads to a loss of protein in the urine (proteinuria).

    A common variation (polymorphism) in the CFI gene has also been associated with age-related macular degeneration (AMD). AMD is a leading cause of vision loss among older adults. It is characterized by damage to the retina and a loss of sharp vision (visual acuity). Researchers suggest that the CFI gene variation that has been associated with AMD changes the way the gene is activated (expressed). It is unclear how this change is related to the development of AMD. A combination of genetic and environmental factors likely determines the risk of developing this complex eye disorder.

    3. Other Names for This Gene

    • AHUS3
    • C3b-INA
    • C3b-inactivator
    • C3B/C4B inactivator
    • C3BINA
    • CFAI_HUMAN
    • complement component I
    • complement control protein factor I
    • complement factor I heavy chain
    • complement factor I preproprotein
    • FI
    • IF
    • KAF
    • Konglutinogen-activating factor
    • light chain of factor I

    The entry is from https://medlineplus.gov/genetics/gene/cfi

    References

    1. Baracho GV, Nudelman V, Isaac L. Molecular characterization of homozygoushereditary factor I deficiency. Clin Exp Immunol. 2003 Feb;131(2):280-6.
    2. Fagerness JA, Maller JB, Neale BM, Reynolds RC, Daly MJ, Seddon JM. Variation near complement factor I is associated with risk of advanced AMD. Eur J HumGenet. 2009 Jan;17(1):100-4. doi: 10.1038/ejhg.2008.140.
    3. Kavanagh D, Richards A, Noris M, Hauhart R, Liszewski MK, Karpman D, Goodship JA, Fremeaux-Bacchi V, Remuzzi G, Goodship TH, Atkinson JP. Characterization ofmutations in complement factor I (CFI) associated with hemolytic uremic syndrome.Mol Immunol. 2008 Jan;45(1):95-105.
    4. Nilsson SC, Trouw LA, Renault N, Miteva MA, Genel F, Zelazko M, Marquart H,Muller K, Sjöholm AG, Truedsson L, Villoutreix BO, Blom AM. Genetic, molecularand functional analyses of complement factor I deficiency. Eur J Immunol. 2009Jan;39(1):310-23. doi: 10.1002/eji.200838702.
    5. Ponce-Castro IM, González-Rubio C, Delgado-Cerviño EM, Abarrategui-Garrido C, Fontán G, Sánchez-Corral P, López-Trascasa M. Molecular characterization ofComplement Factor I deficiency in two Spanish families. Mol Immunol. 2008May;45(10):2764-71. doi: 10.1016/j.molimm.2008.02.008.
    6. Richard I. The genetic and molecular bases of monogenic disorders affectingproteolytic systems. J Med Genet. 2005 Jul;42(7):529-39. Review.
    7. Servais A, Frémeaux-Bacchi V, Lequintrec M, Salomon R, Blouin J, Knebelmann B,Grünfeld JP, Lesavre P, Noël LH, Fakhouri F. Primary glomerulonephritis withisolated C3 deposits: a new entity which shares common genetic risk factors with haemolytic uraemic syndrome. J Med Genet. 2007 Mar;44(3):193-9.
    8. Vyse TJ, Morley BJ, Bartok I, Theodoridis EL, Davies KA, Webster AD, WalportMJ. The molecular basis of hereditary complement factor I deficiency. J ClinInvest. 1996 Feb 15;97(4):925-33.
    9. Vyse TJ, Späth PJ, Davies KA, Morley BJ, Philippe P, Athanassiou P, Giles CM, Walport MJ. Hereditary complement factor I deficiency. QJM. 1994Jul;87(7):385-401. Review.
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