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