Tuning cell fate: from insights to vertebrate regeneration

Abstract

Epigenetic interventions are required to induce reprogramming from one cell type to another. At present, various cellular reprogramming methods such as somatic cell nuclear transfer, cell fusion, and direct reprogramming using transcription factors have been reported. In particular, direct reprogramming from somatic cells to induced pluripotent stem cells (iPSCs) has been achieved using defined factors that play important epigenetic roles. Although the mechanisms underlying cellular reprogramming and vertebrate regeneration, including appendage regeneration, remain unknown, dedifferentiation occurs at an early phase in both the events, and both events are contrasting with regard to cell death. We compared the current status of changes in cell fate of iPSCs with that of vertebrate regeneration and suggested that substantial insights into vertebrate regeneration should be helpful for safe applications of iPSCs to medicine.

Keywords: Dedifferentiation; Direct Conversion; Pluripotency; Primed Conversion; Reprogramming; Transcription Factors; Vertebrate Regeneration; induced Pluripotent Stem Cells (iPSCs).

Figure 1. Vertebrate regeneration in mouse neonates hearts.

Figure 2. Scheme of cell fate changes based on Waddington’s epigenetic landscape. Direct reprogramming is the reversion of terminally differentiated cells such as fibroblasts to a pluripotent state. Direct conversion is the alteration from one cell type to another, such as fibroblasts to cardiomyocytes. Dedifferentiation is defined as a reversion of specialized phenotypes into an undifferentiated state. Transdetermination is the switching of somatic stem/progenitor cells from one determined state to another closely related state.^,

Figure 3. Study design of nuclear reprogramming Transcriptional factor (TF)-mediated reprogramming (upper left); reprogramming TFs such as Oct4, Sox2, Klf4, and c-Myc (OSKM) are introduced into iPSCs from somatic cells. Cell fusion (upper right); two or more different types of cells are fused using methods such as electrical cell fusion, polyethylene glycol cell fusion, or Sendai virus-induced cell fusion. Somatic cell nuclear transfer (SCNT; lower); nuclei from donor cells are transferred into enucleated oocytes. Blastocysts derived from SCNT-oocytes can then be cultured as nuclear transfer-embryonic stem cells (NT-ESCs) or can be implanted into pseudopregnant mice to produce offspring.

Figure 4. Cardiac differentiation of OSKM-mediated mouse embryonic fibroblasts (MEFs) via primed conversion (A) Phase contrast microscopic view of OSKM-mediated MEFs 14 d after OSKM infection. OSKM-mediated MEFs were differentiated into cardiomyocytes. (B) Reverse transcription polymerase chain reaction (RT-PCR) analysis of gene expression. (C) Fluorescent microscopic view with immunofluorescent staining of OSKM-mediated MEFs, which were stained with DAPI, OCT4, Gata4, and α-actinin antibodies.