Scientists uncover new genetic cause of lupus

9 May 2018
A team of scientists and clinicians at VIB, KU Leuven and UZ Leuven has identified a novel mutation causing an unusual form of the autoimmune disease lupus. The genetic analysis of a Belgian family sheds new light on the disease mechanisms underlying lupus, which could possibly yield new therapeutic approaches for patients. The findings are published in the Journal of Allergy and Clinical Immunology in the week leading up to World Lupus Day.

Lupus is an autoimmune disorder, meaning that the body’s immune system mistakenly attacks its own tissues. Lupus can affect multiple organs but its cause is often not clear. Usually a combination of genetic and environmental factors is at play.

The Leuven researchers have now discovered a novel genetic mutation in a patient that presented at the age of 12 with both lupus and problems in the ability of the immune system to fight common infections. This unusual combination of symptoms was quite puzzling.
By analyzing the patient’s DNA and that of the parents, the scientists could trace the problem down to a specific mutation in the gene encoding the Ikaros protein. The protein in turn binds DNA to regulate the expression of other proteins.

Erika Van Nieuwenhove, clinician and scientist at VIB-KU Leuven, explains how the mutation caused the patient’s immune system to be hyperactive: “Because of the mutation, Ikaros can no longer bind its target DNA properly. We also observed that certain immune cells of the patients were hyperactive, even in the absence of stimulation. The link between both observations turned out to be CD22, a protein that normally dampens the immune response. In normal conditions, Ikaros stimulates the expression of this inhibitor, but this was not the case in this patient.”

About 5 million people worldwide have lupus, but a causative mutation in Ikaros is very rare. “Small changes in Ikaros are associated with susceptibility to adult-onset lupus, but because the effects are weak it is hard to work out what Ikaros is doing to the immune system,” explains prof. Adrian Liston (VIB-KU Leuven), who heads the lab for translational immunology and is lead author of the study. “In this particular family, however, a mutation created a large change in Ikaros, causing early-onset lupus. The mutation was strong enough to allow us to work out how changes in Ikaros cause lupus and immune deficiency.”

Although the patient in this study has a very rare form of lupus, the discovery nevertheless helps to map the overall disease mechanisms, underscores prof. Carine Wouters, pediatric rheumatologist at University Hospitals Leuven and co-lead of the study: “The mechanism we uncovered in this patient could also be meaningful in a different context with other patients. Now that we understand what goes wrong in this particular case, it could help us think of better targeted treatments for others as well.”

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Publication
A kindred with mutant Ikaros and autoimmunity, Van Nieuwenhove et al., 2018 Journal of Allergy and Clinical Immunology

Funding
The study was supported by ERC and FWO.

Questions from patients
A breakthrough in research is not the same as a breakthrough in medicine. The realizations of VIB researchers can form the basis of new therapies, but the development path still takes years. This can raise a lot of questions. That is why we ask you to please refer questions in your report or article to the email address that VIB makes available for this purpose: patienteninfo*Replace*With*At*Sign*vib.be. Everyone can submit questions concerning this and other medically-oriented research directly to VIB via this address.


Carine Wouters, Adrian Liston, Erika Van Nieuwenhove, Stephanie Humblet-Baron
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