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Friday, July 29, 2011

Genome sequencing finally provides treatment

Ever since the human genome was sequenced over a decade ago, people have been wondering when this new font of information would be used to treat disease.  For the Beery family, that day is today.

At age two, the Beery twins were diagnosed with cerebral palsy.  However, as the children grew, it became clear that this diagnosis did not explain their symptoms.  At six, they were rediagnosed with a disease called ‘dopa-responsive dystonia’, which is treatable by administering the neurotransmitter dopamine.  This worked until the kids were in their teens, when one of them began to have breathing problems.

At this point, the children’s mother brought them to the Baylor Human Genome Sequencing Center for genetic analysis.  Both twins, their parents and the twins’ older brother had their genomes sequenced.  The geneticists found that the twins had inherited two dysfunctional copies of the gene for sepiapterin reductase (SPR).  In other words, each of their parents had one mutated copy of the gene and one normal copy, and the twins were unlucky enough to have inherited both mutated copies.  SPR is not only responsible for dopamine production, but also for the production of serotonin and noradrenalin, two other neurotransmitters.

Upon acquiring this new information, the children’s doctor began supplementing the twins with not only dopamine, but also serotonin.  Within a month, the twins showed a dramatic improvement.  To be clear, this treatment protocol was chosen specifically because of the sequencing data.  Without the genome sequences of the family, doctors would never have known to take this course of action.

Interestingly, the two parents had two completely different mutations in their SPR genes.  The father’s mutation led to a protein with the wrong amino acid inserted in the middle, whereas the mother’s mutation led to a severely shortened protein.  The researchers speculate that the two types of mutation may be responsible for different, though less severe symptoms in the parents.