A potential enhancer fragment from upstream of erm (most of the region of overlap between the GMR9D11 and GMR9D10 fragments - lacks 350bp at the 3' end of the overlap) followed by the core promoter and 5' UTR of Hsp70 is fused upstream of the z second intron followed by sequences encoding the transmembrane domain of Hsap\CD4 fused to tdTomato. An endoplasmic reticulum export signal from Hsap\KCNJ2 is fused to the C-terminus of the tdTomato sequences. 3'UTR and polyA sequences from His2Av are present downstream of the coding region.