Fig. 3. Loss of SLIT2 function causes the formation of supernumerary ureteric buds. Expression of a Hoxb7-GFP transgene marks nephric duct-derived epithelia in mouse embryos at 11.5 days of gestation (anterior towards the top). (Left) The normal ureteric bud has emerged from the nephric duct. (Right) Supernumerary ureteric buds have formed anterior to the normal one in a Slit2-null mutant.