Somatic remobilization of pT2 βGFP in double transgenic tadpoles. Outcross of double transgenic hopper frogs resulted in progeny that inherited both transgenes. In rare instances, we identified double transgenic tadpoles that express intense levels of the GFP transgene reporter in individual cells or in small groups of cells. The change in GFP expression seen in these somatic cells is likely to be due to sporadic remobilization of the pT2 βGFP transposon and the change in GFP intensity is likely due to the influence of the local chromatin environment at the novel integration site. The region of each tadpole shown (dashed box) is indicated on the cartoon inset. (a) Tail of a double transgenic tadpole with a single muscle cell expression intense GFP (arrow). (b) Double transgenic tadpole with high-level GFP expression in a subset of cells in the brachial cartilage (arrow). The immobilized tadpole was also photographed using a dsRED filter and the two images were overlaid to demonstrate that this animal had inherited the CAGGS-SB 10;γcRFP transgene (RFP expression in the lens is indicated by the white arrowhead). GFP: green fluorescent protein; RFP: red fluorescent protein.