In silico analysis of potential off-target sites to gene editing for Mucopolysaccharidosis type I using the CRISPR/Cas9 system: Implications for population-specific treatments.

Mucopolysaccharidosis type I (MPS I) is caused by alpha-L-iduronidase deficiency encoded by the IDUA gene. Therapy with CRISPR/Cas9 is being developed for treatment, however a detailed investigation of off-target effects must be performed. This study aims to evaluate possible off-targets for a sgRNA aiming to correct the most common variant found in MPS I patients (p.Trp402*). A total of 272 potential off-target sequences was obtained and 84 polymorphic sites were identified in these sequences with a frequency equal to or greater than 1% in at least one of the populations. In the majority of cases, polymorphic sites decrease the chance of off-target cleavage and a new PAM was created, which indicates the importance of such analysis. This study highlights the importance of screening off-targets in a population-specific context using Mucopolysaccharidosis type I as an example of a problem that concerns all therapeutic treatments. Our results can have broader applications for other targets already clinically in use, as they could affect CRISPR/Cas9 safety and efficiency.