Function of 2A peptide in pregastrulation embryos. (A-A") E2.5, (B-B") E4.0 and (C-C") E5.5 embryos expressing Tom-2A-GFP ubiquitously under the control of a CAG promoter. The embryos shown represent the F2 generation with respect to the founder F0 transgenic mouse. In all the embryos shown, the transgene was inherited from a heterozygous father. Cells in both embryonic as well as extra-embryonic tissues show segregation of TdTomato and enhanced green fluorescent protein (EGFP) to mutually exclusive cellular compartments, indicating 2A function in both lineages. (A, B, C) EGFP fluorescence. (A', B', C') TdTomato fluorescence. (A", B", C") Merge of EGFP (green) and TdTomato (magenta) fluorescence. The scale bar in (A) represents 50 μm and applies to all panels.