Credit: Salk Institute
Genome editing technology allows for seamless correction of disease-causing mutations in cells from patients with β-thalassemia, investigators have reported in Genome Research.
The team noted that β-thalassemia results from inherited mutations in the hemoglobin beta (HBB) gene, which prompt reduced HBB expression in red blood cells, as well as anemia.
The only established curative treatment is hematopoietic stem cell transplant, but this requires a matched donor.
Gene therapy could eliminate this need.
To correct HBB mutations directly in a patient’s genome, Yuet Wai Kan, MD, of the University of California, San Francisco, and his colleagues first generated induced pluripotent stem cells (iPSCs) from patients’ skin cells.
The team then used CRISPR/Cas9 technology to precisely engineer a double-strand DNA break at the HBB locus in the iPSCs, allowing a donor plasmid with the corrected sites to be efficiently integrated, thus replacing the mutated sites.
The donor plasmid also contained selectable markers to identify cells with corrected copies of the gene. These selectable markers were subsequently removed with transposase and a second round of selection, generating a seamless, corrected version of HBB in the patient’s genome.
The investigators found the corrected iPSCs could differentiate into mature blood cells, and these blood cells showed restored expression of hemoglobin.
However, the team said a lot more work is needed before these cells could be transplanted to treat a patient with β-thalassemia.
“Although we and others are able to differentiate iPSCs into blood cell progenitors as well as mature blood cells, the transplantation of the progenitors into mouse models to test them has, so far, proven very difficult,” Dr Kan said. “I believe it will take quite a few more years before we can apply it in a clinical setting.”
