An international team of researchers used DNA sequencing to spot cases of difficult-to-diagnose diseases in infants – marking the first time this technology is used in the clinic.
Sequencing – decoding thousands of genes simultaneously – has been used since 2009 to uncover genes related to diseases in laboratories, New Scientist explains.
BUT NOW, real patients who don’t know what’s wrong with them and don’t know their family history of the disease can work with clinicians who have few clues about what genes are causing the problem… and have results!
In particular, the researchers looked at mitochondrial diseases – a group of neuromuscular disorders caused by abnormally functioning mitochondria (the energy powerhouse of our cells). They’re found in one out of every 5000 people.
These sorts of disease are tough to diagnose because of their wide variety of genetic causes and symptoms (which include blindness, seizures, vomiting, and muscle pain, for example). Current methods for diagnosis are based on evaluation, standard genetic testing, and some biochemical testing – which could take years. And even then, these data don’t always catch the disease.
- They selected 42 unrelated infants with known mitochondrial diseases.
- For each child, they sequenced the DNA of the mitochondrial genome.
- These include the 100 genes that have been linked to these diseases and the 1000 or so genes involved in mitochondrial biology.
- Then the team compared the patients' genomes with databases of genetic variation recorded in the general population to distinguish between harmless variations and disease-causing ones.
They found that for severe forms of mitochondrial diseases in infants, about 25% of – previously intractable – cases can be genetically solved using sequencing.
- 10 of the children had mutations in genes previously linked to mitochondrial diseases, and so they could be given a precise diagnosis.
- Mutations not previously associated with any disease were found in another 13 children.
The findings should help shape our expectations of the success rate of sequencing when its transferred into a clinical setting.
Image: JohnGoode via Flickr