DNA-binding protein that binds to the 5'-CAAG-3' core sequence. May function as a transcriptional repressor. Seems to act as a transcriptional antagonist of NKX2-5. May play an important role in the development of craniofacial structures such as the eye and ear. Expressed in neural crest-derived tissues, including, nerve ganglia and cranial mesenchyme. On 9.5 dpc expressed in the trigeminal (V) ganglion. On 10.5-11 dpc, expressed in the eye, second branchial arch and the dorsal root ganglion. On 11.5-12 dpc, expressed in the lens and neural epithelium of the eye. On 14-16 dpc, expressed in the sympathetic ganglon and dorso-lateral mesenchyme near the developing ear. Belongs to the HMX homeobox family.