D esigner therapies are treatments tailored to a specific disease, and nowhere is the need greater for new therapies than in a group of nervous system disorders, known as “neurodegenerative diseases.”

Many of these diseases are common and well-known, such as Alzheimer’s or Parkinson’s disease. However, some are very rare, genetic disorders that are the consequence of a defective gene. In all these diseases, a mutant protein that misfolds causes the degeneration and death of neurons. One effective therapeutic strategy is to prevent the rogue protein from ever being made.

Spinocerebellar ataxia type 7 (SCA7) is one such disease in which nerves in different parts of the brain, including the eye, degenerate, which leads to blindness and difficulty walking, speaking, and balancing. SCA7 is dominantly inherited — which means that you just need one bad copy of the mutation to cause disease. The disease occurs when a short section of DNA that encodes ataxin-7 gene is erroneously repeated — like a word in a book printed two or three times. In this case, three chemical units of the DNA sequence — C-A-G — are repeated over and over.