We find that the BMP target gene Id1 imposes a proximal posterior identity on undifferentiated cells, priming them towards mesoderm.
HOX genes assign the correct identity to undifferentiated body segments along several developmental axes (Krumlauf, 1994; Carroll, 1995; Moens and Selleri, 2006; Wellik, 2007; Zakany and Duboule, 2007).
Therefore, in agreement with recent data for other SOX2+ve progenitors in various adult epithelial tissues (Arnold et al., 2011), a proportion of embryonic SOX2 SOX9-positive progenitorSOX2 SOX9-positiventiated and maintain their identity until adulthood.
The identity, stability, and undifferentiated state of lines can be assessed with less than 5 μg of genomic DNA and 100 ng of total RNA.
We found that short tandem repeat (STR) analysis, human leukocyte antigen (HLA) typing, single nucleotide polymorphism (SNP) genomic analysis, mitochondrial DNA sequencing, and gene expression analysis by microarray can be used to fully describe any hESC culture in terms of its identity, stability, and undifferentiated state.
Thus each of these cell types retains some identity despite all being undifferentiated, a function suggested to be linked to the H3K27 methylase activity of Ezh2 [36].
For this purpose, they have to remain in an undifferentiated state and maintain their stem cell identity over a series of cell divisions.
The tests include measures of identity, stability, and self-renewal, and the undifferentiated state of the cells.
The pathways implicated in cell fate decisions are clearly relevant to transformation as most forms of breast cancer involve deregulation of signalling pathways (Egg, Fgf, Notch, Wnt) that also determine cell identity when cells are initially specified from undifferentiated precursor cells [ 53].
Recently, a combination of three defined factors (Ascl1, Brn2 and Myt1) has been identified to be able to directly convert fibroblasts into induced neuronal (iN) cells, indicating that the cell identity switch could occur without going through an undifferentiated state [32].
The loss of RB1 in an ERMS or an ARMS model modifies the tumour phenotype to mimic an undifferentiated pleomorphic sarcoma (Rubin et al, 2011) or a pleomorphic RMS identity (Kikuchi et al, 2013), respectively.
