Transcription factor involved in specification of neuronal cell types and which is required for inner ear and hypothalamus development. Expressed in the developing CNS, including a specific expression in vestibular structures throughout inner ear development. It is expressed in neuronal and neuroepithelial cells during development of the CNS and PNS. Mice display a perturbation in cell fate determination in the lateral aspect of the otic epithelium results in reduced cell proliferation in epithelial cells, which includes the vestibular sensory patches and semicircular duct fusion plates, as well as in the adjacent mesenchyme. Consequently, enlargement and morphogenesis of the pars superior of the otocyst to form a complex labyrinth of cavities and ducts is blocked, as indicated by the lack of any distinguishable semicircular ducts, persistence of the primordial vestibular diverticula, significant loss in the 3 cristae and the macula utriculus, and a fused utriculosaccular chamber. Mice lacking both Hmx2 and Hmx3 show a complete loss of balance, postnatal dwarfism, defects in neuroendocrine system, disturbed hypothalamic-pituitary axis and subsequent die. Defects caused in mice lacking both Hmx2 and Hmx3 can be rescued by expressing the Drosophila Hmx protein. Belongs to the HMX homeobox family.