CRISPR/Cas9 can cure Sickle Cell Disease in Stem Cells

Sashreek Ganguli, Amity University Kolkata

Sickle cell disease (SCD) is a set of blood disorders inherited from parents. It is a genetic disorder caused due to A-to-T base mutation within codon 6 of the HBB/Beta-globin gene (which is a part of haemoglobin A/ HgbA) responsible for the glutamic acid to valine substitution. It affects the motility of RBCs in the bloodstream as the RBCs tend to deviate from their original shape to a sickle-like shape. This results in reduced oxygen transport and also affects erythropoiesis causing various difficulties. Stem cell transplantation (allo-HSCT) is a remedial therapy for SCD. However, recipients often suffer from graft-vs-host disease and/or the problems of long-term immune-suppression. 

Here, CRISPR/Cas9-mediated HBB gene correction of SCD patient-derived hematopoietic stem cells (HSCs) along with autologous transplantation presents a new pattern in gene therapy. A variety of CRISPR/Cas9-based gene correction methods for HBB have now been validated in human hematopoietic stem and progenitor cells (HSPCs). A promising technology for gene correcting human HSPCs involves CRISPR/Cas9-mediated genome cutting along with recombinant adeno-associated virus serotype 6 (AAV6) homologous recombination (HR)-based repair. Hence, a humanized globin-cluster SCD mouse model was used to analyse Cas9-AAV6-mediated HBB-correction in functional HSCs within the preview of autologous transplantation. The results showed 10x longer RBC half-lives in gene-corrected HSCT recipients.  Recipients with the high levels of HgbA had reduced occurrence of abnormal RBC morphology, RBC sickling.  25% allelic correction, in the myeloid lineage specifically, is enough to get these results. 

Source: Cas9-AAV6 Gene Correction of Beta-Globin in Autologous HSCs Improves Sickle Cell Disease Erythropoiesis in Mice, Adam C. Wilkinson1,2,5*, Daniel P. Dever1,3,5, Ron Baik1,3, Joab Camarena1,3, Ian Hsu1,2, Carsten T.Charlesworth1,2, Chika Morita1,2, Hiromitsu Nakauchi1,3,4*, Matthew H. Porteus1,3* https://www.biorxiv.org/content/10.1101/2020.10.13.338319v1