Instead of generating embryonic stem cell lines via nuclear transfer, Hwang's group produced the stem cells from days-old embryos, a technique that had already been established by James Thomson at University of Wisconsin in 1998.
Chemo-radiotherapy specifically degrades muscle mass, and depresses the function of mitochondria, the tiny structures that act as the boiler room of the cell, generating energy.
Changing the quantities of proteins such as the one made by PSD-93 would probably change the nature of the affected cell quite radically, and might even be responsible for generating the different types of nerve cell that are known to exist.