Map of disease-causing mutations in neurodevelopmental disorders and cancer revealed

Scientists have created the first extensive map showing how all possible genetic changes can affect health in the gene DDX3X, leading to valuable insights into the underlying mechanisms of neurodevelopmental disorders and cancer.

The new technique outperforms rivals that only rely on AI, revealing the significance of 90 per cent of previously unexplained genetic changes' impact on health. It promises to speed up diagnosis and bring new avenues for treatment.

Harnessing cutting-edge gene editing technologies, researchers focused their attention on the DDX3X gene, to directly assess the impact of over 12,000 genetic changes. A quarter of these alterations were identified as stopping the DDX3X protein from working properly.

The findings, published today in Nature Communications, are freely available to doctors so that they can be immediately used to help diagnose patients. This will facilitate diagnosis of DDX3X-related neurodevelopmental disorder and may stimulate the development of new treatments.

The researchers are applying this technique at scale to many other genes relevant for neurodevelopmental disorders and cancer, teaming with scientists around the world to form the Atlas of Variant Effect Alliance for future discoveries.

Since 2015, the DDX3X gene has been linked to a specific neurodevelopmental disorder, mainly affecting girls and women. DDX3X-related neurodevelopmental-disorder is typically associated with intellectual disability, developmental delays, and often includes features such as seizures. Genetic changes in the gene have also been previously linked to certain forms of cancer, but it was unclear whether this caused too much or too little activity of the DDX3X protein.

Diagnosing developmental disorders is highly challenging, especially in young children where symptoms may be still developing. Families often have many medical appointments and undergo many tests before they receive a specific diagnosis. Detecting these early through genetic screening can greatly enhance treatment effectiveness and improve quality of life for individuals affected3 but until now there has been limited understanding of which harmful genetic changes to look out for.

In this new study, the scientists set out to uncover the impact of all possible genetic changes within the DDX3X gene on protein function and health, including neurodevelopmental disorders and cancer.

Unlike computer-based predictive tools, the team directly tested thousands of these genetic changes by artificially altering the genetic code of human cells grown in a dish, in a process known as ‘saturation genome editing’. To understand the effects of having these genetic alterations, they compared the experimental data with health data from the UK Biobank cohort, and from databases of genetic changes seen in people with neurodevelopmental disorders and cancer.

They identified that 3,432 of the 12,776 different genetic changes prevented the protein from working properly. For most of these genetic changes, doctors previously could not predict whether they affected health. Using the technique, the team were able to discover the significance of up to 93 per cent of genetic changes for which the impact on health was previously unknown. They were able to achieve an accuracy of 99 per cent in pinpointing the DDX3X genetic changes relevant to neurodevelopmental disorders.

Genetic changes in DDX3X have also been known to occur in cancer. However, it was not known whether these genetic changes caused too much or too little activity of the DDX3X protein. The current study was able to demonstrate that the genetic changes seen in cancer prevent the DDX3X protein from working properly, an important insight that will facilitate the development of new cancer treatments targeting the gene.

An author of the study said: “We currently can read the letters in the genetic code (A, C, T and G), but often do not understand what they mean. Even apparently minor changes can profoundly impact a child's development in genetic conditions. Our approach, which goes beyond computation to assess the effect of mutations, enables us to reliably differentiate between harmless and harmful rare genetic changes. As part of the Atlas of Variant Effects Alliance, we will continue to uncover essential insights hidden within our genetic code.”

A senior group leader said: “DDX3X is altered in a range of cancers and in particular in childhood brain cancers. Understanding exactly which mutations are disease-causing facilitates diagnosis and can help ensure patients get the most suitable treatment for their disease.”