Michael Holmes comments on CRISPER Sickle Cell research

http://www.nature.com/news/crispr-deployed-to-combat-sickle-cell-anaemia-1.20782

In a paper published 12 October in Science Translational Medicine¹, researchers reported some success in correcting the mutation in mice, though they concede that human applications are still years away. The efficiency of the process is also slightly too low for practical use, cautions author Jacob Corn, a biochemist at the University of California, Berkeley.

The refined technique will be a boon for researchers looking at other applications of gene editing, says Michael Holmes, vice-president of research at Sangamo Biosciences in Richmond, California. But it also highlights another problem: the attempts at gene editing leave plenty of genes with a deletion where the Cas9 enzyme cut. Some of those deletions could result in abnormal haemoglobin production — causing another serious condition called β-thalassaemia.
Sangamo also ran up against this problem, Holmes says, and decided to try a different approach. The company, and several others in the field, are using gene editing to disrupt expression of a gene that suppress the production of fetal-haemoglobin: a form of haemaglobin that is expressed in the developing fetus and resists sickling. Boosting the production of fetal-haemoglobin could thereby reduce the amount of sickle-shaped haemoglobin in adults.