New gene analysis provides a better diagnosis of mental disabilities

New gene analysis provides a better diagnosis of mental disabilities

Analysis of the whole genetic mass, so-called whole-genome sequencing, can be used to diagnose intellectual disability with greater precision than other genetic analysis methods.

For the individual who undergoes a survey of the entire genetic mass, only a regular blood test is required.

Next step: genetic diseases

At the beginning of 2020, the Karolinska University Laboratory will be one of the first in the world to use the method as the first diagnostic test for intellectual disability in newborns, children and adults. In the future, it can also be used in fetal diagnostics, and further developed to make other diagnoses - for example, for serious diseases suspected of having genetic background.

A new analysis tool, developed at the Karolinska Institutet, will now be introduced as the first line of clinical diagnostics at the Karolinska University Laboratory.

An estimated 1.5 percent of Sweden’s population has an intellectual disability, which in most cases, is caused by genetic changes. These can range from small point mutations (one or a few base pairs) within individual genes or repetition of some base pairs, to significant structural chromosome changes involving one or more genes.

Various genetic anomalies behind intellectual disability

Today, most people with intellectual disabilities are offered a clinical investigation, which includes genetic analyzes with so-called gendosis array and DNA analysis for so-called Fragile X syndrome. With these tests, about 12 percent get a molecular causal diagnosis. Based on the clinical picture, other genetic tests are then ordered – from analysis of single genes to analysis of the entire genome (whole-genome sequencing).

– The technology gap in genetic diagnostics has led to the discovery of many new genetic abnormalities in recent years that cause intellectual disabilities. Currently, there are more than 800 different diagnoses described in the literature, which means that it can take a long time to diagnose, says Anna Lindstrand, associate professor at the Department of Molecular Medicine and Surgery.

She has led a study at Karolinska Institutet where researchers have developed their own analysis tools. In combination with whole-genome sequencing, they can detect both point mutations, structural chromosome aberrations, and genetic repeats.

The researchers paralleled both gene-array and whole-genome sequencing for 100 individuals. They were then able to show that more than twice as many patients (27 percent) were able to get a causal diagnosis with their in-house developed genome analysis compared to the array technology.

Cheap and versatile test

– Genome sequencing has become so affordable in a short time that it can now be used as a comprehensive test to find different genetic changes. The price of sequencing a person’s entire genetic mass is now only marginally higher than other genetic analyzes used today to detect genetic anomalies, says Anna Lindstrand.

As one of the first clinical laboratories in the world, the Karolinska University Laboratory will now introduce whole-genome sequencing as the first-line clinical diagnostic of intellectual disability.

Conclusion

The research is a multidisciplinary collaboration through the Karolinska Undiagnosed Diseases Program (K-UDP). In recent years, the aim of the collaboration has been to improve the diagnosis of rare syndromes, skeletal dysplasia, neuromuscular diseases, metabolic diseases, immune deficiencies, and isolated intellectual disability. Specifically, the focus has been to develop and deepen the analysis of whole-genome sequencing data to identify more types of genetic anomalies with this test.

Scientific article:

From cytogenetics to cytogenomics: whole-genome sequencing as a first-line test comprehensively captures the diverse spectrum of disease-causing genetic variation underlying intellectual disability .

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