The CreERT2 loxP system allows obtaining an inducible knockout in cells expressing tamoxifen inducible Cre recombinase CreERT2 and containing loxP sites flanking the target gene by adding 4 hydroxy tamoxifen to the culture medium zithromax 5 day pack a professor of hematology oncology and director of the bone marrow and stem cell transplant unit at the University of California, Los Angeles UCLA