Dissecting Richter's Syndrome in a Multiplexed CRISPR-Based Mouse Model Reveals Key Changes in MYC, Interferon and BCR Signaling Underlying Transformation

Richter's syndrome (RS) represents one of the foremost challenges in CLL management, and its pathogenesis remains largely undefined. We recently leveraged CRISPR-Cas9 in vivo gene editing to develop mouse models of RS by engineering multiplexed loss-of-function lesions typical of CLL (Atm, Trp53, Chd2, Birc3, Mga, Samhd1) in early stem and progenitor cells [Lineage - Sca-1 + c-kit + (LSK)] from MDR-Cd19Cas9 donor mice. These animals express Cas9-GFP in a B-cell restricted fashion and the leukemogenic MDR lesion, which mimics del(13q) when the sgRNA-transduced LSK cells are transplanted in CD45.1 immunocompetent recipients. Through these methods, we observed not only development of CLL, but also transformation into RS, and even captured a stage where CLL and RS were co-existing in the same animal (CLL/RS).