A group of international researchers have identified a genetic mutation thats responsible for causing lupus.<\/p>\n
Its the first time that a mutation on a specific gene has been linked to the autoimmune disease. While not all patients carry this mutation, the researchers believe that their discovery will help to find better treatments.<\/p>\n
A paper describing the discovery is published in Nature.<\/p>\n
Senior author Dr Vicki Athanasopoulos, a researcher at the Australian National Universitys John Curtin School of Medical Research, says that researchers have known that theres a genetic component for a while but its recent advances in genetic technology that have allowed them to make this breakthrough.<\/p>\n
We know that the environment plays a big role, and hormones, and things like that. But from studies using identical twins, monozygotic twins, we know that there is a genetic component, says Athanasopoulos.<\/p>\n
Theres been these databases, which contain genes that we think are associated with lupus. But this is the first time weve actually been able to prove that a particular gene, when its mutated, will cause lupus.<\/p>\n
A lot of that is because of advances in technology where we can now generate mutations in the genomes of animals, for example or cell lines using whats called CRISPR-Cas9 technology.<\/p>\n
The problematic gene itself codes for a protein called Toll-like receptor 7, or TLR7. It operates in the immune system, where it helps to sense RNA that comes from viruses.<\/p>\n
The researchers examined a mutation in the TLR7 gene that was present in a seven-year-old girl with severe lupus.<\/p>\n
When they used CRISPR to cause this mutation in mice, the mice also developed lupus-like symptoms.<\/p>\n
Mice carrying the mutant TLR7 protein developed a condition that mimicked severe autoimmune disease in human patients, providing evidence that the TLR7 mutation causes lupus, says lead author Grant Brown, a PhD student at ANU.<\/p>\n
This evidence, combined with other experiments on mutated TLR7 proteins, allowed the researchers to conclude that this gene was a culprit.<\/p>\n
Theres more than one mutation on the TLR7 gene that might have this effect.<\/p>\n
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We did have other lupus patients that had different mutations in the same gene, says Athanasoloulos.<\/p>\n
We looked at some of those, and they seem to behave in a similar way, in that the mutation makes the protein overactive.<\/p>\n
But they also found lupus patients who dont have a mutated TLR7 gene.<\/p>\n
Thats what were trying to unravel: what is causing disease in those particular patients? says Athanasopoulos.<\/p>\n
The TLR7 gene may also play a role in similar chronic conditions.<\/p>\n
We strongly believe that TLR7 and the pathway that it acts in might actually be important in other autoimmune diseases, says Athanasopoulos.<\/p>\n
We are looking to see how important this gene is in other autoimmune diseases. But we suspect that its going to play a role.<\/p>\n
And the genetic mutation potentially explains why lupus is nine times more common in women than in men: the TLR7 gene sits on the X chromosome.<\/p>\n
This means females with an overactive TLR7 gene can have two functioning copies, potentially doubling the harm, explains senior author Professor Carola Vinuesa, a researcher at ANU and the UKs Francis Crick Institute.<\/p>\n
The researchers are hoping that their CRISPR-based mouse model can be used to test potential lupus treatments which target the TLR7 mutation.<\/p>\n
This newly generated mouse model provides us with a framework to continue to understand the immune system and how autoimmune diseases develop in humans, says Brown.<\/p>\n
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