魚崎 英毅

BACKGROUND: Cardiomyocyte loss occurs in acute and chronic cardiac injury, including cardiotoxicity due to chemotherapeutics like doxorubicin, and contributes to heart failure development. There is a pressing need for cardiac-specific therapeutics that target cardiomyocyte loss, preventing chemotherapy complications without compromising chemotherapeutic efficacy. OBJECTIVES: The authors employed massively parallel combinatorial genetic screening to find microRNA (miRNA) combinations that promote cardiomyocyte survival. METHODS: CombiGEM (combinatorial genetics en masse) screening in a cardiomyocyte cell line was followed by validation in the original cell type and screening in primary cardiomyocytes. The top combination was tested in mouse and developing zebrafish models of doxorubicin cardiotoxicity. RNA sequencing provided insight into possible mechanisms. RESULTS: Multiple miRNA combinations protected cardiomyocytes from doxorubicin in vitro. The most effective (miR-222+miR-455) appeared to act synergistically, and mitigated doxorubicin cardiotoxicity phenotypes in murine and zebrafish in vivo models. RNA sequencing revealed overlapping and synergistic regulation of relevant genes and biological processes in cardiomyocytes, including mitochondrial homeostasis, oxidative stress, muscle contraction, and others. CONCLUSIONS: We identified miR-222 and miR-455 as a combination with potential therapeutic applications for cardioprotection. This study furthers our knowledge of the cardiac effects of miRNAs and their combinations and demonstrates the potential of CombiGEM for cardioprotective combinatorial therapeutic discovery.

SpCas9 and AsCas12a are widely utilized as genome-editing tools in human cells. However, their relatively large size poses a limitation for delivery by cargo-size-limited adeno-associated virus (AAV) vectors. The type V-F Cas12f from Acidibacillus sulfuroxidans is exceptionally compact (422 amino acids) and has been harnessed as a compact genome-editing tool. Here, we developed an approach, combining deep mutational scanning and structure-informed design, to successfully generate two AsCas12f activity-enhanced (enAsCas12f) variants. Remarkably, the enAsCas12f variants exhibited genome-editing activities in human cells comparable with those of SpCas9 and AsCas12a. The cryoelectron microscopy (cryo-EM) structures revealed that the mutations stabilize the dimer formation and reinforce interactions with nucleic acids to enhance their DNA cleavage activities. Moreover, enAsCas12f packaged with partner genes in an all-in-one AAV vector exhibited efficient knock-in/knock-out activities and transcriptional activation in mice. Taken together, enAsCas12f variants could offer a minimal genome-editing platform for in vivo gene therapy.

Abstract Background Base editing via CRISPR-Cas9 has garnered attention as a method for correcting disease-specific mutations without causing double-strand breaks, thereby avoiding large deletions and translocations in the host chromosome. However, its reliance on the protospacer adjacent motif (PAM) can limit its use. We aimed to restore a disease mutation in a patient with severe hemophilia B using base editing with SpCas9-NG, a modified Cas9 with the board PAM flexibility. Methods We generated induced pluripotent stem cells (iPSCs) from a patient with hemophilia B (c.947T>C; I316T) and established HEK293 cells and knock-in mice expressing the patient’s F9 cDNA. We transduced the cytidine base editor (C>T), including the nickase version of Cas9 (wild-type SpCas9 or SpCas9-NG), into the HEK293 cells and knock-in mice through plasmid transfection and an adeno-associated virus vector, respectively. Results Here we demonstrate the broad PAM flexibility of SpCas9-NG near the mutation site. The base-editing approach using SpCas9-NG but not wild-type SpCas9 successfully converts C to T at the mutation in the iPSCs. Gene-corrected iPSCs differentiate into hepatocyte-like cells in vitro and express substantial levels of F9 mRNA after subrenal capsule transplantation into immunodeficient mice. Additionally, SpCas9-NG–mediated base editing corrects the mutation in both HEK293 cells and knock-in mice, thereby restoring the production of the coagulation factor. Conclusion A base-editing approach utilizing the broad PAM flexibility of SpCas9-NG can provide a solution for the treatment of genetic diseases, including hemophilia B.