PHOX2B and ocular melanoma: The Phox2 genes are involved in OM development, and since a recent paper suggested a role for Phox2a together with Lmx1b in the generation and control of OMNs and red nucleus neurons (RNNs) [4], it is likely that Phox2a and Phox2b expressing cells in the midbrain are (immature) visceral and somatic motorneurons.