Hypermethylation and inactivity of the FMR1FMR1 gene is responsible for Fragile X Syndrome, the most common form of intellectual disability in males. Rudolph Jaenisch’s group at the Whitehead Institute for Biomedical Research, Cambridge, developed a version of dCas9-Tet1 which they used to activate FMR1 in induced pluripotent stem cells (iPSCs) from patients with Fragile X Syndrome . When the iPSCs with reactivated FMR1 were differentiated into neurons, neural function was rescued and remained rescued after transplant into mouse brain. Jaenisch’s group also showed that they could also use their system to activate FMR1 in post-mitotic neurons.
Juan Carlos Izpisua Belmonte of the Salk Institute for Biological Studies, CaliforniaCalifornia and his team designed guide RNAs to bring transcriptional activators with dCas9 to activate genes of interest . Instead of fixing the mutated gene in a disease, their approach is to upregulate other genes in the disease pathway that can compensate for the malfunctioning gene. In mouse models for kidney disease and muscular dystrophy their approach improved kidney and muscle function.
Acetylation modifications to histones, the proteins, which package DNA into chromatin change the conformation of the chromatin. Charles Gersbach and Timothy Reddy at Duke UniversityDuke University, fused human acetyltransferase, p300 to dCas9. The fusion protein causes histone H3 lysine 27 to become acetylated at target sites, which activated target genes .
Epigenetic CRISPR/Cas9 is a modified form of the gene editing technology CRISPR, designed to activate genes without cutting DNA by adding or removing methyl groups in specific positions.
This technique allows researchers to see how changes affect gene expression and has been tested in cultured mouse cells and live mice.