Hoxb3 negatively regulates Hoxb1 expression in mouse hindbrain patterning

► We generated a gain-of-function Hoxb3Tg transgenic mutant which expressed Hoxb3 in hindbrain r4. ► Hoxb3Tg embryos lost Hoxb1 expression in the mutant r4 and phenocopy Hoxb1 null mutants. ► By molecular analyses we showed that Hoxb3 can suppress Hoxb1 expression directly. ► We demonstrated that Hoxb3 can restrict Hoxb1 expression to r4 by a negative regulatory mechanism.