To knock down Lmo3 expression in mice, we injected single- cell embryos with lentivirus expressing either shLmo3.8 or shScr. We reasoned that infection of individual mice at the embryo stage with shLmo3 lentivirus would yield animals with a range of Lmo3 expression due to variation in the number of viruses integrated into the genome of each founder (Lois et al., 2002) as well as potential effects of the integration site, generating an allelic series for behavioral testing. After behavioral testing (see below), the brains of founder animals were analyzed for expression of GFP, which is encoded by the integrated virus. We found that GFP was widely expressed in the brains of animals containing either integrated shScr or shLmo3.8 lentivirus. GFP fluorescence was visible as bright spots in cell bodies and processes of neurons in many brain regions, including cells in the cortex, nucleus accumbens, and cerebellum (Fig. 3A–F). No gross differences were observed in the levels and patterns of GFP fluorescence between groups of animals that had been injected with shScr or shLmo3.8 lentivirus. However, the levels of GFP fluorescence
