Brain diseases linked to nerve cell junction defects

LONDON (Reuters) - More than 135 brain diseases including autism, chronic pain, schizophrenia and dementia are linked to defects in proteins in the junctions between nerve cells, scientists have found.

Researchers have been able for the first time to map the protein structure of human synapses, the junctions between nerve cells responsible for transmitting information, offering scientists a new way of looking at diseases that affect millions of people around the world.

It also opens potential new ways of finding and developing drugs for brain diseases, and may in future allow doctors to make genetic diagnoses of the conditions, said Seth Grant, the neuroscientist at Cambridge University's Sanger Institute who led the study.

"We now recognize that these synapse proteins are the molecular basis of many brain diseases," he told reporters before presenting his findings at the Forum for European Neuroscience in Amsterdam on Monday. "We know of no other molecular structure which is responsible for more brain diseases -- so we think it's a major discovery."

Grant's team used a technique called proteomics to analyze all the proteins in human brain cells. Humans have around a million billion brains cells and these are connected by synapses, which play a pivotal role because they create circuits that allow the brain to learn and remember things.

The scientists found around 1,500 proteins in human synapses, each of which is encoded by a gene. They then managed to link genetic defects in some of these with key diseases such as autism, bipolar disorder, depression and schizophrenia.

"By understanding the composition of the synapse, we can also ask which proteins are important to diseases, and therefore get a sense of the disease burden that the synapse is involved with," Grant said.

"Rather than thinking that a gene causes a particular disease, what we're seeing now is that the gene mutation disrupts the (protein) complexes that cause the disease. We found that defects in the genes that encode these human synapse proteins are really a major cause of diseases."

In a follow-up study using mice, Grant's team found that by using various drugs to change the proteins in the synapse, the link to disease was also altered.

Grant said his team now planned to investigate whether the links between defects in synapse proteins and disease that they found in mice are also borne out in humans.

"If they are, then it has the potential to radically refocus scientists' approach to the study of brain diseases," he said.

(Editing by David Stamp)