In {TAIL ~ other embodiments} the cell or {HEAD ~ its ancestors} was genetically altered with a vector to place X under control of an endogenous transcriptional control element 
In
In { TAIL ~ other embodiments } the cell or { HEAD ~ its ancestors } was genetically altered with a vector to place X under control of an endogenous transcriptional control element
REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH