Publication in Molecular Therapy

12 January 2017

A paper by Ellen van Agtmaal from the group of Rick Wansink and Bé Wieringa, Dept. of Cell Biology hit the cover of the January issue of Molecular Therapy (Cell Press) with a gene editing strategy for myotonic dystrophy.

Myotonic dystrophy (DM) is the most frequent inherited neuromuscular degenerative disorder in adults, which manifests itself at different ages with variable expression of progressive skeletal muscle wasting, myotonia, heart and gastrointestinal problems, insulin resistance, cataract and alterations in cognitive functions and behavior. DM’s multisystemic symptoms are caused by expansion of an unstable (CTG•CAG)n triplet repeat in the DMPK gene and the overlapping DM1-antisense gene.

The Nijmegen group, in collaboration with colleagues from Paris and Glasgow, explored a DNA-directed therapeutic strategy for treatment of DM. They demonstrate that excision of the triplet repeat from an expanded DMPK allele in myoblasts from DM patients or a DM mouse model can be achieved at high frequency by dual CRISPR/Cas9-cleavage at either side of the repeat sequence. Unexpectedly, single cleavage in either its 5’ or 3’ flank promotes uncontrollable deletion of large segments from the expanded repeat, rather than formation of short indels usually seen after double-strand break repair. Precise removal of the repeat corrected myogenic capacity of patient muscle cells as well as the abnormal nucleocytoplasmic distribution and protein binding behavior of mutant DMPK transcripts. Dual CRISPR/Cas9-guided excision of the (CTG•CAG)n tract is thus applicable for the development of isogenic corrected DM cell lines for fundamental research and will also provide new opportunities for somatic gene therapy for patients with DM.

Ellen van Agtmaal (first author) and Rick Wansink and Bé Wieringa (senior authors) published their findings in Molecular Therapy.