Robo4-lacZ knock-in mouse. (A) Schematic of WT or ETSmut LacZ knock-in targeted alleles. The LacZ cDNA, SV40 polyadenylation signal (pA), neomycin resistant gene (Neo), and exons (E1, E4-E6) are indicated. (B) Organs were harvested from F1 wild-type (WT) or ETSmut male heterozygous mice carrying the LacZ gene, and processed for whole-mount staining with X-Gal. (C) β-galactosidase activity of protein extracts from various organs of WT (■) or ETSmut (red bars) knock-in mice. B indicates brain; H, heart; Lu, lung; Li, liver; K, kidney; Sm, skeletal muscle. Data represent mean plus or minus SE of 4 replicates. *P < .05 between organs from WT and ETSmut mice. (D) Serial sections were prepared from organs of WT or ETSmut knock-in mice and stained with CD31 or LacZ antibody. (E) Serial sections were prepared from tumor xenografts prepared in WT or ETSmut mice and stained with X-Gal. (F) Whole-mount E10 embryos (top panel) or day-10 embryoid bodies (bottom panels) from WT and ETSmut knock-in mice or ES clones were stained with X-Gal, respectively.