Fig. 2 |. Direct reprogramming across germ layers.

Direct reprogramming can induce cell fate conversions between cell lineages that are derived from the same embryonic germ layer but can also cross the germ layer barrier. That is, cells derived from one germ layer can be converted to cell types originating from another germ layer. Fibroblasts originating from the mesoderm have been used as starting cells in most direct reprogramming experiments owing to their availability and high plasticity. Other cell types, such as macroglial cells from the ectoderm and α-cells from the endoderm, have also been used for successful direct reprogramming. The combinations of reprogramming factors used for each cell type conversion are shown; pioneer factors that are crucial for successful direct reprogramming are highlighted. Small molecules and microRNAs are also used for direct reprogramming (not shown).