Direct Reprogramming of Human Fibroblasts into Induced Neural Progenitor Cells Using Suicide Gene Embodied Episomal Vectors for Rapid Selection of Exogenous DNA-Free Cells

Direct neural reprogramming involves a rapid conversion of somatic cells into neural cells without passing through the intermediate pluripotent stage. This phenomenon can be mediated in the starting somatic cells by the introduction of lineage-specific master transcription factors or by pluripotency factors routinely used in iPS cell generation. In the latter process known as Pluripotency factor-mediated Direct Reprogramming (PDR), the pluripotency factors are used to elicit epigenetic changes producing a permissive state in the starting cells which are then driven to the neural lineages by simple manipulations of the culture conditions. When genes are exogenously introduced to achieve such conversion, their persistent expression after completion of the reprogramming can affect the properties of the resulting cells. Here, we describe a robust method for direct neural reprogramming using the episomal vectors that incorporate a suicide gene scFCY1 (encoding cytosine deaminase) that allows rapid and efficient generation of a homogenous population of transgene-free human-induced neural progenitor cells (hiNPCs). The resulting NESTIN+/PAX6(+)/CDH2(+) hiNPCs can be expanded and cryopreserved and can be further differentiated into neurons and glia.