Genes linked to spinal arthritis

A team of international researchers have identified several new genetic variants that are involved in a type of incurable spine arthritis — ankylosing spondylitis (AS) — offering hope for novel treatments for those with the condition.

AS affects around 200,000 Britons, causing debilitating joint pain, stiffness, inflammation, curvature of the spine and back pain. Over time their spines can end up becoming fixed, resulting in the person being unable to bend or move freely.

Co-author of the new study, Professor Matt Brown from the University of Queensland in Australia, said: 'Our work shows the great value of partnering genetics research with functional investigations to determine the basic biology which leads to common diseases such as ankylosing spondylitis, the causes of which have remained an enigma for so long'.

The latest research, published in the journal Nature Genetics, involved a genome-wide association study of 1,787 British and Australian people affected by AS and a control group of 4,800 healthy people. By looking at the differences in the genetic make-up of all those in the study, the team identified genetic regions associated with the condition. As reported in  BioNews 541, six areas were already known to be involved with the condition; this work has increased the number of genetic loci 'convincingly associated with AS' to nine, as well as identifying a further four new loci.

While effective treatments can suppress the inflammation caused, there are no therapies for the long-term pain, loss of movement and disability. 'As we understand better how these genetic factors operate, we may be able to use that understanding to develop new therapies', said Professor Peter Donnelly, director of the Wellcome Trust Centre for Human Genetics at the University of Oxford, and lead author of the study. However, in its report NHS Choices warn that such approaches will take time.

One genetic variant in particular, ERAP1, had an interesting interaction with another gene that is already known to be associated with AS — HLAB27. While carriers of HLAB27 have up to 80 times the risk of developing AS as those who do not carry it, those with HLAB27 as well as a particular version of ERAP1 have four times less risk of AS than normal.

'The changes in ERAP1 that have a protective effect make [HLAB27] work less well', Professor Donnelly said. 'It seems to slow down the immune system, so it can't cause problems. That naturally leads to the suggestion of possible drug therapies that do the same thing'.

The cricketer Mike Atherton has lived with the condition since he was in his early teens, recalling in the Times that doctors initially dismissed his complaints of sharp pains below his ankles and in his knees as 'growing pains'.