Genetic Test Pinpoints Cause of Patient Illness

Successful treatment highlights value of whole-genome sequencing

June 17, 2011

An individualized approach to diagnosis and treatment - using whole-genome sequencing - could move out of the research lab and into the doctor's office in the next few years.

About a decade ago, scientists decoded the human genome, creating a gene-by-gene map of our DNA. In the decade since, genetic research has accelerated, but mostly it's stayed in the laboratory. Now, genetic science is taking its first steps into medical practice.

The Beery twins were born in 1996, and were diagnosed with cerebral palsy two years later. But as the children got older, their symptoms suggested a different diagnosis, a lack of the neurotransmitter dopamine. Around age six, the twins started taking a drug called L-dopa, which dramatically lessened their muscle spasms and other symptoms.

Fast forward a decade or so, and new symptoms appeared. To see what other factor might be at work, a team at the Baylor College of Medicine in Texas analyzed DNA samples from each of the twins, looking for a mutation that might be responsible.

Genetic tests then available didn't find anything unusual, however researcher Matthew Bainbridge says sequencing the entire genome of each of the twins later identified mutated copies of a gene called SPR (sepiapterin reductase).

"But mutations in SPR mean that, not only do you not make dopamine in the brain, you also don't make serotonin. And so these kids were getting this L-dopa treatment, which helped them with their lack of dopamine, but they weren't getting anything for their serotonin," he says.