Filaggrin is essential for the regulation of epidermal homeostasis. Within the stratum corneum, filaggrin monomers can become incorporated into the lipid envelope, which is responsible for the skin barrier function. Alternatively, these proteins can interact with keratin intermediate filaments. Filaggrin undergoes further processing in the upper stratum corneum to release free amino acids that assist in water retention.
It has been shown that almost 50% of all severe cases of eczema may have at least one mutated filaggrin gene. R501X and 2284del4 are not generally found in non-Caucasian individuals, though novel mutations (3321delA and S2554X) that yield similar effects have been found in Japanese populations. Truncation mutations R501X and 2284del4 are the most common mutations in the Caucasian population, with 7 to 10% of the Caucasian population carrying at least one copy of these mutations.
The barrier defect seen in filaggrin null carriers also appears to lead to increased asthma susceptibility and exacerbations. Filaggrin deficiency is one of the top genome-wide genetic determinants of asthma, along with the variants found that regulate ORMDL3 expression.
In early infancy, the penetrance of filaggrin mutations may be increased by household exposure to cats.
^ abOvaere P, Lippens S, Vandenabeele P, Declercq W (September 2009). "The emerging roles of serine protease cascades in the epidermis". Trends Biochem. Sci.34 (9): 453–63. doi:10.1016/j.tibs.2009.08.001. PMID19726197.
^Weidinger S, Illig T, Baurecht H, Irvine AD, Rodriguez E, Diaz-Lacava A et al. (July 2006). "Loss-of-function variations within the filaggrin gene predispose for atopic dermatitis with allergic sensitizations". J. Allergy Clin. Immunol.118 (1): 214–9. doi:10.1016/j.jaci.2006.05.004. PMID16815158.
^Nomura T, Sandilands A, Akiyama M, Liao H, Evans AT, Sakai K et al. (February 2007). "Unique mutations in the filaggrin gene in Japanese patients with ichthyosis vulgaris and atopic dermatitis". J. Allergy Clin. Immunol.119 (2): 434–40. doi:10.1016/j.jaci.2006.12.646. PMID17291859.
^Palmer CN, Irvine AD, Terron-Kwiatkowski A, Zhao Y, Liao H, Lee SP et al. (April 2006). "Common loss-of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis". Nat. Genet.38 (4): 441–6. doi:10.1038/ng1767. PMID16550169.
^Basu K, Palmer CN, Lipworth BJ, Irwin McLean WH, Terron-Kwiatkowski A, Zhao Y et al. (2008). "Filaggrin null mutations are associated with increased asthma exacerbations in children and young adults". Allergy63 (9): 1211–7. doi:10.1111/j.1398-9995.2008.01660.x. PMID18307574.
^Palmer CN, Ismail T, Lee SP, Terron-Kwiatkowski A, Zhao Y, Liao H et al. (July 2007). "Filaggrin null mutations are associated with increased asthma severity in children and young adults". J. Allergy Clin. Immunol.120 (1): 64–8. doi:10.1016/j.jaci.2007.04.001. PMID17531295.
^Henderson J, Northstone K, Lee SP, Liao H, Zhao Y, Pembrey M et al. (April 2008). "The burden of disease associated with filaggrin mutations: a population-based, longitudinal birth cohort study". J. Allergy Clin. Immunol.121 (4): 872–7.e9. doi:10.1016/j.jaci.2008.01.026. PMID18325573.
^Tavendale R, Macgregor DF, Mukhopadhyay S, Palmer CN (April 2008). "A polymorphism controlling ORMDL3 expression is associated with asthma that is poorly controlled by current medications". J. Allergy Clin. Immunol.121 (4): 860–3. doi:10.1016/j.jaci.2008.01.015. PMID18395550.