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Universal CRISPR-Cas9 Mutation Correction Strategy in Human Pluripotent Stem Cells

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Review of “A Universal Approach to Correct Various HBB Gene Mutations in Human Stem Cells for Gene Therapy of Beta-Thalassemia and Sickle Cell Disease” from STEM CELLS Translational Medicine by Stuart P. Atkinson

Current CRISPR/Cas9 genome-editing approaches require a specific design strategy for each different mutation that we hope to correct; this becomes a problem in cases such as the HBB gene, for which over 200 mutations have been identified [1] and linked to diseases such as Beta-thalassemia and sickle cell anemia.

In an attempt to increase efficiency, researchers from the laboratory of Linzhao Cheng and Zhaohui Ye (Johns Hopkins University) have recently reported a “universal” CRISPR/Cas9 strategy to correct any and all mutations present in the entire HBB gene in patient-derived induced pluripotent stem cells (hiPSCs) [2]. Will this new STEM CELLS Translational Medicine study provide a simple and effective means to restore HBB protein expression in iPSC-derived cells as part of a potentially exciting new therapeutic strategy? 

Cai et al. first derived iPSC lines from two β-thalassemia patients containing differing HBB mutations; both iPSC lines displayed the capacity to differentiate into erythrocytes, but both lacked HBB protein expression. To solve this problem, the authors designed and applied a universal strategy applicable to any mutations present in the HBB gene, entailing the application of Cas9 and two validated guide RNAs for the targeted insertion of the entire HBB coding cDNA into exon 1 of the HBB locus in mutant iPSCs. 

Encouragingly, directed differentiation of corrected iPSCs led to the generation of HBB protein-expressing erythrocytes, raising the hope that this universal CRISPR/Cas9 approach may represent an effective means to return lost HBB protein function to cells irrespective of the mutation as a first step towards treating disorders such as Beta-thalassemia and sickle cell anemia.

To stay up to date with more CRISPR/Cas9 and iPSC-based studies and potential treatments for a range of mutation-associated diseases, stay tuned to the Stem Cells Portal!

References

  1. Weatherall DJ, Phenotype—genotype relationships in monogenic disease: lessons from the thalassaemias. Nature Reviews Genetics 2001;2:245.
  2. Cai L, Bai H, Mahairaki V, et al., A Universal Approach to Correct Various HBB Gene Mutations in Human Stem Cells for Gene Therapy of Beta-Thalassemia and Sickle Cell Disease. STEM CELLS Translational Medicine 2018;7:87-97.