Individuals carrying extra copies of a cluster of genes encoding a family of small antimicrobial proteins are at increased risk of developing psoriasis, reports a study online in Nature Genetics. Psoriasis is a common inflammatory skin disease affecting up to 2% of the population in developed countries.
Recently, scientists have recognized that some individuals carry more than two copies of certain genes, while others carry less, and have speculated that these so-called 'copy number variants' might influence an individual's risk of developing common diseases. One such region, present at a range of 2-12 copies per individual in the population, contains a cluster of genes encoding a family of secreted proteins known as beta-defensins. Since beta-defensins are expressed in skin and can induce inflammation in response to infections or other environmental triggers, John Armour and colleagues speculated that variation in beta-defensin copy number might influence the risk of developing psoriasis. In two independent studies involving individuals from the Netherlands and Germany, the authors found that individuals with psoriasis had, on average, more copies of the beta-defensin genes compared to individuals without the disease.
Beta-defensins are components of the innate immune system that serve to protect against a wide range of infectious agents. They are rapidly induced in response to infection or injury and can trigger the release of other proteins, such as the interleukins IL-8, IL-18 and IL-20, that promote inflammation and which have a known role in psoriasis.
John Armour (University of Nottingham, UK)
Abstract available online.
(C) Nature Genetics press release.
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