HDR-mediated gene editing preserves regulation

Mutations in recombination activating gene 1 (RAG1) can cause severe combined immunodeficiency, but as the gene is tightly regulated, constitutive expression after gene therapy raises concerns for immune dysregulation.

Now, researchers at the San Raffaele-Telethon Institute for Gene Therapy (SR-Tiget) in Milan have developed a CRISPR-Cas9 HDR-mediated approach for integrating a corrective sequence into the human RAG1.

In-frame insertion into exon 2 drove physiologic human RAG1 expression and activity in HSPCs from patients with high gene correction efficiency. When these cells were xenotransplanted into immunodeficient Rag1–/– mice, they led to improved B cell production and overcame the T cell differentiation block.

Anna Villa and Maria Carmina Castiello, both at SR-Tiget, were senior and first authors of the study published yesterday in Science Translational Medicine. You can read it here.