GENE TARGETING OF X-CHROMOSOME-LINKED CHRONIC GRANULOMATOUS-DISEASE LOCUS IN A HUMAN MYELOID-LEUKEMIA CELL-LINE AND RESCUE BY EXPRESSION OFRECOMBINANT GP91(PHOX)

The X chromosome-linked chronic granulomatous disease (X-CGD) locus, w hich encodes the gp91phox subunit of the phagocyte respiratory-burst o xidase cytochrome b, was disrupted by homologous recombination in the PLB-985 human myeloid cell line to develop an in vitro model of X-CGD. Superoxide formation was absent in targeted cells after differentiati on to granulocytes but was rescued by stable transfection and expressi on of wild-type gp91phox cDNA. The targeted cell line should be useful in experiments aimed at defining functional regions within gp91phox b y expression of mutant gp91phox cDNAs, complementing studies of natura lly occurring mutations in X-CGD. In addition, the mutant line provide s a model system in which to establish an experimental basis for the t reatment of X-CGD patients with gene replacement therapy. Rescued clon es containing even modest amounts of recombinant gp91phox had respirat ory-burst activity comparable to the wild-type PLB-985 tine, suggestin g that functional correction of X-CGD neutrophils may not require high -level expression of gp91phox.