AILSA CHANG, HOST:
A new study shows how certain genes can lead to brain disorders like autism, epilepsy and schizophrenia. NPR's Jon Hamilton reports that the research also hints at ways to prevent or treat those disorders.
JON HAMILTON, BYLINE: Scientists have identified hundreds of genes that are associated with autism and other disorders of brain development. Dr. Sergiu Pasca of Stanford University says finding all these genes was a good first step.
SERGIU PASCA: The challenge now is to figure out what they're actually doing, how disruptions in these genes are actually causing disease. And that has been really difficult.
HAMILTON: Because you can't do genetic experiments on humans. You can experiment on animal brains, but they don't really develop anything that looks like autism or schizophrenia. So Pasca and a team of scientists tried an approach using clumps of human brain cells called brain organoids.
PASCA: We can actually make different parts of the nervous system in a dish from stem cells.
HAMILTON: The team used these organoids to study how genes affect special brain cells called interneurons, which are thought to play a role in several psychiatric disorders. Pasca says that during pregnancy and the first years of life, these brain cells must complete a remarkable journey.
PASCA: Interneurons are born in deep regions of the brain, and then they have to migrate all the way to the cortex. So now you can imagine that during that migration a lot of things could go awry.
HAMILTON: Pasca's team simulated the migration of interneurons by creating two types of organoids. One resembles an area deep in the brain called the subpallium, where most interneurons are generated. Pasca says the other organoid resembles the cerebral cortex, where interneurons are supposed to end up.
PASCA: And then we've put them together - allow these interneurons to move towards the cerebral cortex.
HAMILTON: With typical organoids, the process worked just the way it's supposed to. So next, Pasca's team used a gene-editing technique called CRISPR to alter the organoids. Pasca says CRISPR allowed them to study the effect of more than 400 genes. And out of those genes...
PASCA: About 10% are actually interfering either with the generation of these interneurons of the cerebral cortex or with their migration.
HAMILTON: Pasca says in the cortex, interneurons serve as a sort of brake, slowing down brain cell activity. Meanwhile, other cells act as the accelerator. Without adequate braking, brain cells can fire out of control, disrupting networks and even causing epileptic seizures. Dr. Guo-li Ming of the University of Pennsylvania says the study shows how variations on lots of different genes could keep interneurons from doing their job.
GUO-LI MING: That would be a disaster. The circuitry would be wrong and the signaling would be wrong. Ultimately, the brain function would be wrong.
HAMILTON: Ming, who was not connected with the study, says her lab would like to use the approach in their own research.
MING: We've been interested in schizophrenia, which is another psychiatric disorder with neurodevelopmental origin.
HAMILTON: Kristen Brennand, a professor of psychiatry at Yale, says scientists' understanding of neurodevelopmental disorders is decades behind their understanding of diseases like cancer.
KRISTEN BRENNAND: Thirty years ago, we might have thought all intestinal cancers should be treated the same way and all lung cancers should be treated the same way. Now we know a lot better.
HAMILTON: Doctors study the genes of cancer cells rather than their location to determine which treatment is most likely to work. Brennand says the new study should help bring a similar approach to the care of patients with autism, epilepsy and schizophrenia.
BRENNAND: This improved genetic understanding will let us do better at diagnosing patients, I hope, but also treating them, because we'll know which pathways we can target to intervene.
HAMILTON: The new study appears in the journal Nature.
Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.
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