Here is another example of CRISPR being used to correct genetic disorders

in this case, Alpha-1 Antitrypsin Deficiency.  One point in common with our Rett's study is that CRISPR was injected into the mice finding the right location to make the genetic changes.  This is different from some other uses of CRISPR where cells, like blood cells, are taken out of the body, and then injected back.  The use of CRISPR is growing.  Check it out.

https://medicalxpress.com/news/2018-07-video-crisprcas9-angelman-syndrome.html