The transgene comprises the cDNA encoding enhanced green fluorescent protein (EGFP), from the jellyfish Aequoria victoria, downstream of the "CAG promoter" -- which consists of the cytomegalovirus immediate early (CMV-EI) enhancer followed by a 1.3-kb DNA segment including the promoter, first exon and first intron of the chicken beta-actin gene, with the 3' splice junction sequence replaced by that of the rabbit hemoglobin beta gene -- and followed by the rabbit beta-hemoglobin polyadenylation signal and 3' flanking sequence.