P385 Development of an AAV-mediated Pentatricopeptide Repeat Protein (PPR) delivery system for treatment of myotonic dystrophy type 1 (DM1)

• Published in: Neuromuscular disorders : NMD Vol. 33; pp. S154 - S155
• Main Authors: Imai, T., Miyai, M., Tamai, T., Ohta, M., Hada, K., Yagi, Y., Nakanishi, O., Mochizuki, H., Nakamori, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2023
• ISSN: 0960-8966; 1873-2364
• DOI: 10.1016/j.nmd.2023.07.349

Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystem disorder caused by expansion of the CTG triplet repeats in the 3′ untranslated region of dystrophia myotonica protein kinase (DMPK). It leads to transcription of toxic RNA containing expanded CUG repeats (CUGexp). Splicing factors such as MBNL1 are sequestered by CUGexp and it interferes with normal splicing programs that are essential for various cellular functions. Pentatricopeptide repeat (PPR) proteins, originally found in plants, regulate organelle RNAs by binding in a sequence-specific manner. In this study, we designed a series of PPR proteins that specifically bind to the hexamer of CUG-repeat RNA (CUG-PPRs) and showed that they selectively bound to the CUG hexamer in vitro and improved typical molecular abnormalities caused by CUGexp in murine DM1 model cells. Finally, we demonstrated that a single systemic administration of a recombinant adeno-associated virus (AAV9) with an expression cassette of CUG-PPR1 protein showed a long-term therapeutic efficacy in DM1 model mice in a correlation with global restoration of abnormal splicing activity. We would like also to present at the session that CUG-PPR1 does not reduce neither DMPK mRNA nor the protein levels in patient-derived cells, unlike nucleic acid-based modalities. These results suggest that systemic delivery of CUG-specific PPR molecules by AAV9 might be an effective approach for the treatment of DM1. Furthermore, this study implies a potential of PPR molecules as a new therapeutic modality that can target pathogenic RNA-mediated diseases.