I am trying to understand the assay for iPS cells in the Takahashi & Yamanaka 2006 paper.
They inserted a beta-geo cassette, which contains the neomycin resistance gene, into the Fbx15 gene. The idea is that the beta-geo cassette will be expressed when Fbx15 will be expressed, thus conferring G418 resistance to only those cells expressing Fbx15.
They say that "Although specifically expressed in mouse ES cells and early embryos, Fbx15 is dispensable for the maintenance of pluripotency and mouse development." Does this mean that Fbx15 will be expressed in induced pluripotent stem cells, and won't be expressed upon differentiation? (What is special about Fbx15 that will distinguish iPS cells from somatic cells, including those that might derive from iPS cells, as when pluripotency is not maintained?)