The transcription factor GATA3 is a downstream effector of Hoxb1 specification in rhombomere 4

In this paper, we show that the transcription factor GATA3 is dynamically e xpressed during hindbrain development. Function of GATA3 in ventral rhombom ere (r) 4 is dependent on functional GATA2, which in turn is under the cont rol of Hoxb1. In particular, the absence of Hoxb1 results in the loss of GA TA2 expression in r4 and the absence of GATA2 results in the loss of GATA3 expression. The lack of GATA3 expression in r4 inhibits the projection of c ontralateral vestibuloacoustic efferent neurons and the migration of facial branchiomotor neurons similar to Hoxb1-deficient mice. Ubiquitous expressi on of Hoxb1 in the hindbrain induces ectopic expression of GATA2 and GATA3 in ventral r2 and r3. These findings demonstrate that GATA2 and GATA3 lie d ownstream of Hoxb1 and provide the first example of Hox pathway transcripti on factors within a defined population of vertebrate motor neurons.