09.2018 | THE SCIENTIST 37© PATRICK LANDMANN/SCIENCE SOURCE© PATRICK LANDMANN/SCIENCE SOURCE
I
f Chengzu Long hadn’t been quite so unlucky, he might never
have attempted to study and treat Duchenne muscular dystro-
ph y. As a PhD student in Eric Olson’s lab at the University of
Texas Southwestern Medical Center, Long had spent years knock-
ing out genes in mice to try to identify their role in muscle devel-
opment and disease, only to find that each of the resulting knock-
outs had no discernible differences from wildtype individuals.
In the fall of 2013, with only about a year left until his
planned graduation, Long decided to take a different approach:
rather than generate yet another knockout mouse that might
again lack a phenotype, he would use the new CRISPR-Cas9
gene-editing technique to correct a disease-causing mutation,
such as those that cause muscle wasting in Duchenne muscular
dystrophy. “I thought to myself, I’m really good at making mice
without a phenotype, so maybe we can use CRISPR to cure an
existing mutation,” says Long, now an assistant professor at New
York University.
Like many muscle disorders, or myopathies, Duchenne is
caused by mutations in a single gene—the X chromosome’s DMD
gene, which encodes the protein dystrophin. Without a functional
dystrophin protein, Duchenne patients gradually lose their mobil-
ity as their muscles degenerate. Most die by their early 30s fromScientists race to develop CRISPR therapies
that could save the lives of kids
with muscle-wasting conditions.BY SANDEEP RAVINDRAN