London | For the first time, scientists in the UKhave discovered a novel function of a protein which is linked to amyotrophic lateral sclerosis and frontotemporal dementia, providing a new insight into the most common genetic cause of the degenerative diseases.
The pioneering study, conducted by scientists from the the University of Sheffield found that the C9orf72 protein, which is encoded by the C9ORF72 gene, functions in the autophagy pathway something which is defective in patients with the most common inherited form of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
Scientists believe that one of the ways the C9ORF72 mutation may cause ALS and FTD is by reducing the amount of C9orf72 protein present in the cells something which is very hard to verify without a clear understanding of the function of the C9orf72 protein.
The world-leading Sheffield Institute of Translational Neuroscience (SITraN) team led by Kurt De Vos and Andy Grierson investigated the role of the C9orf72 protein in nerve cells and found it regulates the initiation of a vital process called ‘autophagy’, which helps the cell to dispose of damaged proteins and cell parts and recycles cell nutrients.
Our study provides compelling evidence that the C9orf72 protein is required for the initiation of autophagy, a pathway essential for the survival of nerve cells, De Vos said. We could also show that that loss of C9orf72 protein function mimics the specific pathology observed in our ALS and FTD patients, De Vos added.
The study, published in the EMBO Journal, provides better understandings of pathways involved in ALS which are of utmost importance to move towards a therapy. It uncovers what happens in the brain cells of people with a gene mutation that is known to cause FTD dementia. Diseases such as ALS and FTD are commonly associated with large protein clumps that accumulate in affected nerve cells.
Our data now shows that the C9orf72 protein is involved in the cellular pathway that should dispose of these clumps and that the autophagy process is defective in the cells of our ALS and FTD patients, said Grierson, fellow lead investigator. Further studies are needed to confirm if defective autophagy contributes to the disease process, but if this bears out then autophagy drugs may be beneficial for patients, Grierson added.
FTD is the second most common form of dementia in those under the age of 65. It can include some upsetting symptoms and very little is known about its underlying causes. Identifying the effects of faulty genes is a vital first step to being able to design drugs that could best help people living with the condition, said Doug Brown, Director of Research at Alzheimer’s Society.
The gene, known as C9ORF72, was only linked to dementia in the last five years so it’s encouraging that advances are being made to piece together the important role it plays in the brain, Brown said. The C9ORF72 gene was identified in 2011 as the most common cause (40 per cent) of all inherited ALS.