Protein-based direct reprogramming of fibroblasts to neuronal lineage cells

Abstract

Direct reprogramming of non-neural lineages to functional neurons holds great potential for neural development, neurological disease modeling, and regenerative medicine. Recent work has shown that single transcription factor Ascl1 can directly reprogram fibroblasts into neuronal cells under co-culture system with glial cells. It is confirmed that Ascl1 is the key driver in the reprogramming of induced neuronal cells (iNCs). However, most reprogramming methods use genetic materials and/or potentially mutagenic molecules to generate iNCs. Herein, we used 30Kc19 protein as a novel fusion partner of transcription factor Ascl1 to induce direct reprogramming of fibroblasts to neuronal cells. We demonstrated soluble expression and stability of Ascl1 protein was increased and maintained by co-expression with 30Kc19 protein, respectively. We confirmed that intracellular delivery of the fusion protein resulted in iNC generation. Protein-induced neuronal cells (p-iNCs) expressed neuronal protein markers (MAP2, Tuj1) and transcriptional genes (Ascl1, Brn2, and Myt1l). Protein-based direct reprogramming system eliminates the potential risk associated with the use of genetic materials. This method is anticipated to be useful for safe generation of patient-specific human neuronal cells for future applications in regenerative medicine.