Lentiviral gene therapy reverts GPIX expression and phenotype in Bernard-Soulier syndrome type C

Bernard-Soulier syndrome (BSS) is a rare congenital disease characterized by macrothrombocytopenia and frequent bleeding. It is caused by pathogenic variants in three genes (GP1BA, GP1BB, or GP9) that encode for the GPIba, GPIbb, and GPIX subunits of the GPIb-V-IX complex, the main platelet surface receptor for von Willebrand factor, being essential for platelet adhesion and aggregation. According to the affected gene, we distinguish BSS type A1 (GP1BA), type B (GP1BB), or type C (GP9). Pathogenic variants in these genes cause absent, incomplete, or dysfunctional GPIb-V-IX receptor and, consequently, a hemorrhagic phenotype. Using gene -edit-ing tools, we generated knockout (KO) human cellular models that helped us to better understand GPIb-V-IX complex assem-bly. Furthermore, we developed novel lentiviral vectors capable of correcting GPIX expression, localization, and functionality in human GP9-KO megakaryoblastic cell lines. Generated GP9-KO induced pluripotent stem cells produced platelets that recapitulated the BSS phenotype: absence of GPIX on the membrane surface and large size. Importantly, gene ther-apy tools reverted both characteristics. Finally, hematopoietic stem cells from two unrelated BSS type C patients were trans-duced with the gene therapy vectors and differentiated to pro-duce GPIX-expressing megakaryocytes and platelets with a reduced size. These results demonstrate the potential of lentivi-ral-based gene therapy to rescue BSS type C.

Automated summary

Bernard-Soulier syndrome (BSS) is a rare congenital disease characterized by macrothrombocytopenia and frequent bleeding. It is caused by pathogenic variants in three genes (GP1BA, GP1BB, or GP9) that encode for the GPIba, GPIbb, and GPIX subunits of the GPIb-V-IX complex, leading to absent or dysfunctional platelet surface receptors. The use of gene editing tools and lentiviral-based gene therapy vectors has shown promise in understanding and potentially rescuing BSS.