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New asthma risk genes suggest link with other diseases

Analysis of a study published in a science journal   |   By Dr Philippa Brice   |   Published 13 September 2011
Study: Identification of IL6R and chromosome 11q13.5 as risk loci for asthma
By: Ferreira M.A.R. et al. (40 authors total)
In: The Lancet
Link: http://dx.doi.org/10.1016/S0140-6736(11)60874-X
What this study set out to do:

Identify novel genetic variants affecting asthma risk and their implications for potential mechanisms underlying the disease. 

How they went about it:

A genome-wide association study (GWAS) was performed in a group of 2,669 asthmatics and 4,528 controls from Australia. These results were combined by meta-analysis with those from an independent study of 26,475 individuals, and seven genetic loci showing links with asthma identified. Finally, these associations were tested in samples from a total of 3,322 asthmatics and 22,036 controls. 

Outcome:

These studies identified a genetic variant in the interleukin-6 receptor (IL6R) gene on chromosome 1 that was highly associated with asthma risk, and a second significant (though less strong) association with a genetic variant on chromosome 11. The other five loci did not show significant association with asthma in the final stage of the study.  

Conclusion:

The two variants in IL6R and on chromosome 11 are novel risk loci for asthma. Other evidence supports a role for the IL6R variant in asthma risk as it is associated with levels of the IL-6 protein receptor, which are increased in patients with asthma and stimulate an immune response in the lung. An existing drug for rheumatoid arthritis (tocilizumab) that binds to IL-6R may also be effective in asthma patients with the novel risk variant. 

Our view:

These new genetic variants identified via analysis of very large numbers of patient and control samples are exciting because they suggest links between asthma and other inflammatory diseases such as Crohn's disease, coeliac disease and psoriasis via overlapping, immune-mediated mechanisms. 

Further discussion:

The authors also note that their results are ‘consistent with the contribution of hundreds or potentially thousands of variants with weak effects on asthma risk’ requiring even larger GWAS for reliable identification.

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