Competing dynamic gene regulatory networks involved in fibroblast reprogramming to hematopoietic progenitor cells.

Direct reprogramming of somatic cells offers a potentially safer therapeutic approach to generate patient-specific hematopoietic cells. However, this strategy is limited by stochasticity of reprogramming. Investigating the gene regulatory networks involved during reprogramming would help generate functional cells in adequate numbers. To address this, we developed an inducible system to reprogram fibroblasts to hematopoietic progenitor cells by ectopically expressing the two transcription factors SCL and LMO2. Transcriptome and epigenome analysis at different stages of reprogramming revealed uniform silencing of fibroblast genes and upregulation of the hemogenic endothelial program. Integrated analysis suggested that the transcription factors FLI1, GATA1/2, and KLF14 are direct targets of SCL/LMO2, which subsequently induce the hematopoietic program. Single-cell RNA sequencing revealed conflicting and competing fate decisions at intermediate stages of reprogramming. Inhibiting signaling pathways associated with competing neuronal fate enhanced reprogramming efficiency. In conclusion, this study identifies early/intermediate reprogramming events and associated pathways that could be targeted to improve reprogramming efficiency.