From Rare to Common: How Rare Diseases Could Advance Schizophrenia Treatment

Rapidly advancing our understanding of rare diseases is a key area of focus for us at WuXiNextCODE. We believe genomics can both transform our ability to understand and diagnose rare conditions, and that this is going to point us is the direction of developing new treatments. At the same time, there is a growing body of evidence and even approved new therapies that show that an understanding of rare diseases can also shed new light on the genetics of complex diseases, such as heart disease, arthritis, and schizophrenia.

Understanding complex diseases is a mammoth challenge because multiple genes are usually involved as well as environmental factors. It’s particularly hard with neurologic conditions. No animal models can really mimic what happens in people’s brains, and human studies usually only provide hints of the information needed to identify potential treatments.

But rare diseases are often caused by single variants that perturb specific and identifiable biological pathways. That’s why recent genetic studies of rare types of early-onset psychosis have inspired so much interest among researchers studying schizophrenia. This disease affects more than 50 million people worldwide, but early-onset cases are very rare, suggesting they may be extreme manifestations.

A new line of inquiry into this condition emerged after a group of our close collaborators at Boston Children’s Hospital, including a scientist now at WuXi NextCODE, used chromosomal microarray analysis and whole exome sequencing in a six-year-old with profound symptoms of psychosis. They discovered this patient had a variation in the ATP1A3 gene, which was not previously associated with schizophrenic symptoms. The team wondered: was that mutation helping cause his symptoms? Would the same mutation be found in other children with early-onset schizophrenia? Could this new lead point to a biological pathway common to many people, young and old, with these same symptoms?

That would be a real breakthrough, both for this child and potentially for many other people.

The Puzzle of Schizophrenia Genetics

Schizophrenia is one of the most serious and common mental illnesses. It is often very difficult to treat, in part because of available drugs’ side effects. There are already about a dozen anti-psychotics on the market for this condition. Besides causing serious side effects, treatment must also usually be life-long. Doctors often have to try different drugs until they find something that works and which the patient can tolerate. Even then, the patient’s response can change over time.

The genetics of the disease are still not well understood. Studies of families and populations show it is heritable – the more affected close relatives someone has, the more likely that person will develop it. Many families are afflicted by both schizophrenia and bipolar disease, suggesting the two conditions are biologically related.  Both conditions seem to be associated with multiple mutations to possibly dozens of genes. Still, even in identical twins – who share exactly the same mutations – it’s not uncommon for only one twin to be affected.  Clearly, there is something other than genes afoot.

Scientists, notably including our colleagues at deCODE genetics, have put their fingers on a few genes and key pathways. Another large genomic study, with more than 30,000 cases and 100,000 controls, pointed to over 100 potential spots in the genome with mutations associated with schizophrenia. Both have found an association with mutations in a region called MHC (Major Histocompatibility Complex), a result that reinforced a then percolating idea that schizophrenia might be related to immune dysfunction.  And then just this week, Chinese researchers reported a new trove of suggestive genetic factors. But despite these massive gene hunts, we are still far from a complete picture of what genes cause this disease and how.

A Promising New Lead?

As described in the BCH blog Vector, The BCH team who found that ATp1A3 mutation in the six-year-old boy decided to do some more digging. The chromosomal microarray analysis showed that he was missing an entire chunk of DNA – one copy of the chromosomal region 16p13.11.  Next, they searched their database and found several other children with variations in that area.  One had a duplication of the 16p13.11 region, rather than a deletion. She had started experiencing hallucinations at the age of 4.  Those findings prompted the BCH researchers to launch a large-scale study, which has already enrolled at least 50 children with early-onset psychosis and will be able to leverage WuXi NextCODE’s informatics and global knowledgebase to find more cases, at BCH and beyond.

The researchers hope that ultimately their studies will not only help children with early-onset schizophrenia but also point to the biological pathways that cause the more prevalent form of the disease, which usually strikes adolescents and young adults.

Such research will hopefully provide firm leads on novel pathways that can be used to identify new drug targets. There is a tremendous need for new medicines. Most of the antipsychotic drugs we have today were developed back in the 1950s and act on the dopamine and/or serotonin receptors. They don’t improve all of patients’ symptoms, and as noted earlier, they can have serious side effects.

By uncovering new biological pathways, groups like the researchers at BCH, able to leverage massive global genomic data like that we are able to provide, aim to uncover such targets and begin the journey to providing better options for patients with rare and common diseases alike.

If you are attending ASHG this month, join us to hear more about how rare disease studies can inform our understanding of common diseases at two of our “Genomes for Breakfast” events:  Using Population Genomics to Understand Common and Rare Disease (Oct. 18), and Using NGS to Diagnose Rare Disease – Experiences from three continents (Oct. 19).