HBB and beta thalassemia: They have been used to deliver CRISPR/Cas9 components to edit the HBB gene that causes beta-thalassemia in hematopoietic stem cells, as well as to correct a genetic mutation that causes Leber congenital amaurosis (LCA) in retinal pigment epithelial cells (Yang et al. 2013; Sun et al. 2017).