Reprogramming Committed Murine Blood Cells to Induced Hematopoietic Stem Cells with Defined Factors

Abstract

Hematopoietic stem cells (HSCs) sustain blood formation throughout life and are the functional units of bone marrow transplantation. We show that transient expression of six transcription factors RUNX1T1, HLF, LMO2, PRDM5, PBX1, and ZFP37 imparts multi-lineage transplantation potential onto otherwise committed lymphoid and myeloid progenitors, and myeloid effector cells. Inclusion of MYC-N and MEIS1, and use of polycistronic viruses increase reprogramming efficacy. The reprogrammed cells, designated induced-HSCs (iHSCs), possess clonal multi-lineage differentiation potential, reconstitute stem/progenitor compartments, and are serially transplantable. Single-cell analysis revealed that iHSCs derived under optimal conditions exhibit a gene expression profile that is highly similar to endogenous HSCs. These findings demonstrate that expression of a set of defined factors is sufficient to activate the gene networks governing HSC functional identity in committed blood cells. Our results raise the prospect that blood cell reprogramming may be a strategy for derivation of transplantable stem cells for clinical application.

Direct Cardiac Reprogramming

“…Recent studies demonstrate that direct reprogramming has the potential to yield a diverse range of cell types from fibroblasts, including neurons, cardiomyocytes, endothelial cells, hematopoietic stem/progenitor cells, and hepatocytes ( Figure 1). [16][17][18][19][20][21][22] These findings indicate that cell fate plasticity is much wider than previously anticipated, and that direct reprogramming may offer a new system to study the mechanisms underlying cell fate decisions during development, which is currently a major focus of investigation in basic biology.…”

“…17 The successful generation of engraftable hematopoietic stem cells required in vivo bone marrow environment, a supportive niche for hematopoietic stem/progenitor cells, emphasizing the importance of microenvironment for cell fate conversion. Another approach to generate hematopoietic stem/ progenitor cells is the induction of hematopoietic progenitors mediated through an endothelial cell intermediate, mimicking the developmental process in embryos in which definitive hematopoiesis emerges via an endothelial-to-hematopoietic transition.…”

Bioinformatic and Genomic Analyses of Cellular Reprogramming and Direct Lineage Conversion

“…With these datasets, investigators are able to generate candidate genes which may be capable of direct conversion as well as use defined lineage specific networks as a benchmark for proper lineage reprogramming. Many of these rely on a study of the gene expression networks in the target cells to confirm proper lineage conversion including hematopoietic stem and progenitor cells (iHSC, iHPC, [4,73,85]), embryonic sertoli-like cells (ieSCs, [13]), endothelial cells (iECs, [33]), and melanocytes (iMels, [101]). …”

Reprogramming finds its niche

“…Earlier this year 7 , another group reported the transformation of mature white blood cells from mice into engraftable HSCs that can form all blood-cell lineages. Reprogramming was accomplished with six transcription factors (Runx1t1, Hlf, Lmo2, Prdm5, Pbx1 and Zfp37), and the cells were matured in vivo to generate iHSCs (Fig.…”

“…Surprisingly, comparison of Sandler and colleagues' protocol with those used to reprogram mouse white blood cells 7 or fibroblasts 5 reveals that each method used a different transcription-factor cocktail to generate iHSCs. This may result from species differences, from the ability of each cell type to respond to different transcription factors or from the different epigenetic state of each cell type — that is, genomic modifications that affect gene expression without changing DNA sequence.…”