Table 1.

Summary of published articles that relate to the mechanism of iPS cell generation and characterization

Ref. No.	Title	Summary	Related subjects
[4]	Cell type of origin influences the molecular and functional properties of mouse induced pluripotent stem cells	iPS cells from mouse fibroblasts, hematopoietic and myogenic cells exhibit distinct transcriptional and epigenetic patterns. Cellular origin influences the in vitro differentiation potentials of iPS cells	Tissue origin and differentiation potential
[5]	Induced pluripotent stem cells and embryonic stem cells are distinguished by gene expression signatures	Genome-wide data suggested that the iPSC signature gene expression differences are due to differential promoter binding by the reprogramming factors. Epigenetic memory of the donor tissue could be reset by serial reprogramming	Epigenetic memory
[6]	Epigenetic memory and preferential lineage-specific differentiation in induced pluripotent stem cells derived from human pancreatic islet beta cells	The pancreatic islet beta cell-derived iPS cells maintained open chromatin structure at key beta-cell genes, together with a unique DNA methylation signature. Those iPS cells demonstrated an increased ability to differentiate into insulin-producing cells compared with ES cells	Tissue origin and differentiation potential
[7]	Incomplete DNA methylation underlies a transcriptional memory of somatic cells in human iPS cells	A systematic comparison of iPS cells generated from hepatocytes, skin fibroblasts and melanocytes showed that iPS cells retain transcriptional memory of the original cells. The persistent expression of somatic genes can be partially explained by incomplete promoter DNA methylation	Incomplete promoter DNA methylation
[8]	Epigenetic memory in induced pluripotent stem cells	IPS cells harbor residual DNA methylation signatures characteristic of their somatic tissue of origin, which favors their differentiation along lineages related to the donor cell. The differentiation and methylation of nuclear transfer-derived pluripotent stem cells were more similar to ES cells	Epigenetic memory
[9]	Donor cell type can influence the epigenome and differentiation potential of human induced pluripotent stem cells	As a consequence of both incomplete erasure of tissue-specific methylation and aberrant de novo methylation, umbilical cord blood- and neonatal keratinocyte-iPS cells were distinct in genome-wide DNA methylation profiles and differentiation potential, implying that iPS cells retain ‘epigenetic memory’ of their tissue of origin	Tissue origin and differentiation potential
[10]	Cancer-related epigenome changes associated with reprogramming to induced pluripotent stem cells	Cancer-related epigenetic abnormalities arise early during reprogramming and persist in iPS cell colonies. These include hundreds of abnormal gene silencing events, patterns of aberrant responses to epigenetic-modifying drugs resembling those for cancer cells	Epigenetic abnormalities
[11]	Immunogenicity of induced pluripotent stem cells	In contrast to ES cells, abnormal gene expression in some cells differentiated from iPS cells can induce T cell-dependent immune responses in syngeneic recipients	Immune responses
[13]	Direct cell reprogramming is a stochastic process amenable to acceleration	The number of cell divisions is a key parameter driving epigenetic reprogramming to pluripotency. Almost all mouse donor cells are theoretically eventually give rise to iPS cells with continued growth and transcription factor expression	Stochastic model
[21]	DNA methylation dynamics in human induced pluripotent stem cells over time	Stochastic de novo methylation of genomic DNA occurs in iPS cell generation. Cell division proceeds in iPS cells after prolonged culture lead to a cell condition that epigenetically more closely resembles that observed in ES cells	Stochastic model
[67]	Enhanced generation of induced pluripotent stem cells from a subpopulation of human fibroblasts	Fibroblasts that expressed SSEA-3 demonstrated an enhanced iPS cell generation efficiency (~eightfold increase), while no iPSC derivation was obtained from the fibroblasts that did not express SSEA-3	Elite model
[30]	Multilineage-differentiating stress-enduring (Muse) cells are a primary source of induced pluripotent stem cells in human fibroblasts	Muse cells that are aleady pluripotent but are non-tumorigenic preexist in mesenchymal cells. In human fibroblasts, iPS cells are generated exclusively from Muse cells but never from non-Muse cells, suggesting that preexisting adult stem cells that are pluripotent selectively become iPS cells, but the remaining cells make no contribution	Elite model