Highly efficient prime editors for mammalian genome editing based on porcine retrovirus reverse transcriptase

Prime editing is a versatile and precise genome-editing tool. Most prime editors (PEs) rely on reverse transcriptase (RT) derived from Moloney murine leukemia virus (MMLV). Here, we established a PE, pvPE, using a RT derived from a porcine endogenous retrovirus (PERV) from a Bama mini-pig. Through various optimization strategies, including RT engineering, structural modifications, and La protein fusion, we gradually upgraded to pvPE-V4. This version achieved 24.38-101.69-fold higher efficiency compared with pvPE-V1 and up to 2.39-fold higher efficiency than another upgraded PE, PE7, with significantly fewer unintended edits across multiple mammalian cell lines. We further show that nocodazole (Noc) significantly enhanced pvPE efficiency by 2.25-fold on average. Using our pvPE system, we efficiently modified three genes simultaneously in porcine fibroblasts and subsequently generated cloned pigs that could serve as valuable models for Alzheimer's disease (AD) in humans. Our results highlight the broad application prospects of pvPE systems in mammalian genome editing.