Specific reasons for the difference in developmental potential are not known. However, different donor cells (stem cells, progenitor cells, and fibroblast cells), which all showed different developmental potential after NT, also expressed different levels of chromatin remodeling genes
and have different patterns of DNA methylation. The difference in chromatin remodeling genes suggests that undifferentiated cells have a different chromatin structure than differentiated cells, and the structure of chromatin may play an important role during reprogramming. The search for an ideal donor cell is certainly not finished.