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Monitoring Stem Cell Research 
of various growth factors in the serum. The cells are, however, are 
cultured on a feeder layer. 
An area of great interest in EG cell derivation is the basis of the 
underlying mechanism for the conversion, derivation or 
transformation (terms reflecting our ignorance of the process) of 
primordial germ cells to EG cells. Kimura et al. (2003) report that the 
loss of a tumor suppressor gene in mice, PTEN (phosphatase and 
tensin homology deleted form chromosome ten, aka MMACl and 
TEPl), leads to a high incidence of testicular teratomas and 
enhances the production of EG cells from PGCs of the mutant mice. 
While it is highly unlikely that the loss of this gene in the culture of 
normal PGCs leads to the derivation of EG cells, it may implicate 
downstream signaling pathways that are involved in cell cycle 
progression, cell survival and cell migration as important players in 
the process. 
PRE-PUBLICATION VERSION 
