A modified cell surface marker gene for transgenic animal studies.

We developed a marker gene encoding a human cell surface molecule called CD8 for use in transgenic animal studies. The CD8 cDNA contains three mutations: one in the extracellular domain which prevents interaction with its ligand MHC class I and the other two in the cytoplasmic domain which inhibit its signalling function. The cDNA was linked to a fragment of the human growth hormone gene and in transgenic animal studies, expression was observed in the appropriate cell types using a CD2 enhancer. The advantage of the CD8 marker gene is that it is incapable of signalling via its only known signalling pathway and its expression can be monitored using monoclonal antibodies and microscopy or flow cytometry.