Bloom-in' flies

Bloom syndrome is a disease characterized by increased tumorigenesis, immunodeficiency and partial sterility. It is caused by mutations in the BLM gene, which encodes a helicase. In the March 30th Science, Kusano et al. describe characterization of the Drosophila Dmblm homolog of BLM (Science 2001, 291:2600-2602). They show that Dmblm corresponds to mus309, which was originally identified in a mutagen-sensitivity screen. Disrupting the Dmblm gene causes mutagen sensitivity and female sterility, whereas transgenic flies expressing Dmblm rescue the mus309 phenotypes. Kusano et al. also show that transgenic flies expressing the DNA-repair gene Ku70 could rescue mus309 phenotypes, implicating Dmblm in the pathways that repair double-strand DNA breaks. Consistently, mus309 male sperm show evidence for increased nondisjunction and chromosome loss.