Researchers at the Memorial Sloan-Kettering Cancer Center (New York, NY) and the University of California (San Francisco, CA) have used a lentiviral vector to introduce functional β-globin genes into hematopoietic stem cells, alleviating β-thalassemia in a mouse model of the disease. Although significant hurdles remain before HIV-1 and related lentiviruses can be considered for gene therapy in humans, the new work demonstrates that the vector can introduce and regulate corrected genes during stem cell development (Nature 406, 82–86, 2000). Previous studies on β-globin gene regulation showed that the locus control region (LCR) upstream of the gene is required for properly regulated gene expression, but earlier gene therapy approaches have been unable to incorporate enough of the LCR to achieve regulated expression. Now, researchers have found that a lentiviral vector can transduce a large portion of the LCR into hematopoietic stem cells, and that the transduced gene remains stably integrated. Michel Sadelain, head of the gene transfer and gene expression laboratory at Sloan-Kettering and senior author on the paper, says the system “could be used as a model for introducing genes in other types of stem cells as well.”