BioCentury
ARTICLE | Translation in Brief

Beyond PAM

How allele-specific CRISPR-Cas9 editing could treat dominant genetic diseases

March 7, 2018 12:37 AM UTC

Researchers from the Massachusetts Eye and Ear Infirmary (MEEI) and Harvard Medical School have created a CRISPR-Cas9 system that can distinguish between mutant and wild-type alleles, potentially enabling the use of CRISPR-based gene editing to treat a wider range of dominantly inherited diseases than conventional CRISPR systems.

Previous studies in mice have demonstrated the feasibility of allele-specific gene editing when the disease-causing allele carries protospacer adjacent motif (PAM) sequences, targeted by wild-type Streptococcus pyogenes CRISPR-associated protein 9 (Cas9), that are not present in the wild-type allele. PAM sites are required for Cas9 binding in most DNA editing applications but many dominant alleles -- those of which one copy is sufficient to cause the disease -- do not harbor PAM sites that differ from the wild-type allele...